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"VAPOR BARRIERS IN RESIDENTIAL CONSTRUCTION: WHEN, WHERE, AND IF TO UTILIZE THEM"

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CAPT FRAILIE DERON L

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THE DEPARTMENT OF THE AIR FORCE AFIT/CL\, BLDG 125 2950 P STREET WPAFB OH 45433

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VAPOR BARRIERS IN RESIDENTIAL CONSTRUCTION: WHEN, WHERE, AND IF TO UTILIZE THEM

Project and Report prepared by

Deron L. Frailie In partial fulfill of the requirements for completion of

Master of Science in Architecture, Construction Management Option Virginia Polytechnic Institute and State University

Fall 2003

5 Dec 03

Committee: Yvan Beliveau, Ph.D and P.E. (Committee Chair)

Michael O'Brien, R.A. Ronald Wakefield, Ph.D.

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Table of Contents

Proposal 4

Abstract 5

Executive Summary 6

1.0 Literature Review for Vapor Barriers in Residential Construction Applications 26

1.1 Introduction 27

1.2 Keywords and Definitions 28

1.3 Review of Literature 29 1.3.1 What is moisture? 29 1.3.2 How is moisture generated? 31

1.3.2.1 UquidFlow 32 1.3.2.1.1 Mass/Storage Walls 32 1.3.2.1.2 Perfect Barriers 33 1.3.2.1.3 Screened Drainage Walls 33

1.3.2.2 Capillary Suction 34 1.3.2.3 Air Movement 34 1.3.2.4 Vapor Diffusion 38

1.3.3 How do you deal with the moisture transport mechanisms? 39 1.3.3.1 Capillary Suction 39 1.3.3.2 Liquid flow 40 1.3.3.3 Evaporation 42 1.3.3.4 Ventilation 42 1.3.3.5 Vapor diffusion and air leakage 43

1.3.4 Why vapor barriers are used today? 46 1.3.5 How do you use a vapor barrier? 48

1.4 Summary 54

1.5 References Cited 56

2.0 The Code Recommendations for Vapor barrier implementation in Residential Construction: Do the recommendations make sense? 59

2.1 Introduction 60

2.2 Standards defined by ASTM 60

2.3 CABO and ICC Code Summaries 62

2.4 What the codes should say...foundation, wail, and ceiling/roof 64 2.4.1 Foundation - slab 64 2.4.2 Foundation - crawl space 66 2.4.3 Foundation - basement 67 2.4.4 Walls 68 2.4.5 Roof/Ceiling 74

2.5 Summary 77


3.0 WUFI Data Results Summary 79

3.1 Background of Software Program, Initial Assumptions, and Limitations 80

3.2 Model Development and Data Interpretations 81 3.2.1 New Orieans Data Results 83 3.2.2 Minneapolis Data ResuHs 84 3.2.3 Roanoke Data Results 86

3.3 Summary 90


4.0 Summary and Conclusions 97

4.1 Summary 98

4.2 Detail Conclusions and Specifics for Foundations, Walls, and Roofs 98 4.2.1 Foundations 98 4.2.2 Walls 100 4.2.3 Roofe 103

4.3 Summary of Lessons Learned 104


Appendix 1 - New Orleans Test Data Ill

Appendix 2 - Minneapolis Test Data 144

Appendix 3 - Roanoke Test Data 177

5.0 Bibliography 226

Proposal The major problem cited by independent residential builders in new housing construction is

moisture related, primarily, rot, decay, and the growth of molds and fungus. First recognized and

investigated in a 1923 Forest Products Laboratory survey of dwellings, condensation and

moisture related problems were witnessed in early exterior structure paint feilure (U.S. Forest

Service, 1949). Current building codes and property standards contribute to the problem since the

methods employed are prescriptive rather than performance oriented, and the code requirements

have tried to create a universal approach for construction rather than looking holistically at the

wall assembly components (Trechsel, Achenbach, and Launey, 1982 and Sherwood and Moody,

1989). The purpose of the proposed project and report will be three fold: 1.) Conduct a review of

the current building codes for residential construction practices (CABO, International Residential

Code and American Society of Testing and Materials) and provide a discussion of the code

prescribed installation methodologies and the information/guidance that should be included; 2.)

Produce a guide of best practices for proper design and detailing of vapor barriers according to

the primary climatic region conditions for several common wall assemblies utilized in residential

construction; and 3.) Analyze common wall assemblies and the associated dew point locations

under several climatic conditions utilizing WUFI, a diffusion modeling software program tiiat helps

predict/compute relative humidity levels which when used in conjunction with the temperature

enables the user to determine the dew point.

Abstract The major problem cited by independent residential builders in new housing construction is

moisture related, primarily, rot, decay, and the growth of molds and fungus. Current building

codes and property standards methods are prescriptive rather than performance oriented. Wall

assembly components should be considered holistically rather than individually (Trechsel,

Achenbach, and Launey, 1982 and Shenwood and Moody, 1989).

The report defines and discusses the physical characteristics and standards of vapor barriers as

provided by the American Society of Testing Materials (ASTM) for the design of building

systems. The Council of American Building Officials, CABO: One and Two Family Dwelling

Code. 1995 Edition. Fourth Printing, and International Code Council, International Residential

Code: For One and Two Family Dwellings, codes will then be summarized, discussed, and

evaluated to determine whether the code recommendations follow the information from the

reviewed literature that has been published with respect to this subject. A recommended

description of how to design the wall systems with respect to vapor barriers is provided. WUFI,

Warme-und Feuchteransport Instationar (Transient Heat and Moisture Transport), a computer

wall-modeling program, was utilized to determine whether the proposed solutions remain valid

once the wall sections were subjected to weather conditions.

The primary conclusion that can be drawn from this report is that the concern when designing,

detailing, and constructing a structure for vapor/moisture is that air moves far more vapor and

moisture than is diffused through the wall cavity materials. Air movement is the movement

mechanism that needs to be addressed in our structures.

Executive Summary

Abstract Current building codes and property standards contribute to tlie moisture problem currently being

experienced in many of our residences. The methods being employed in the codes [Council of

American Building Officials (CABO) and the International Code Councils (ICC)] are prescriptive

rather than performance oriented, and have tried to create a universal approach for construction

rather than looking holistically at the individual wall assembly components and specific structure's

design (Trechsel, Achenbach, and Launey, 1982 and Shenwood and Moody, 1989). The

following paper contains a summary of lessons learned during the course of a review of literature,

a summary of the ASTM vapor bamer standards, a detailed examination of the current existing

building codes in relation to vapor barriers, and concludes with recommendations that are climate

specific with regard to the foundation, walls, and roofing systems most commonly utilized in

residential construction today.

Keywords Vapor barriers/vapor diffusion retarders, building codes, air baniers, moisture, and condensation

Introduction Condensation and moisture related problems were first recognized and investigated in a 1923

Forest Products Laboratory survey of dwellings with early exterior paint failure on residential

houses (U.S. Forest Service, 1949). It has more recently been reported, "with the exception of

structural errors, 90% of building construction problems are associated with water" and the

harmful effects related to its penetration into our structures (Trechsel, Achenbach, and Launey,

1982). Buildings continue to be a source of health problems because of the accumulation of

moisture and the subsequent growth of mold and fungi within our structure's envelope.

Current building codes and property standards contribute to this problem because the methods

being employed are prescriptive rather than performance oriented. The codes have tried to

create a universal approach for construction rather than looking holistically at the wall assembly

components and specific structure's design (Trechsel, Achenbach, and Launey, 1982 and

Sherwood and Moody, 1989).

A major assumption that this paper espouses is that air moves far more moisture vapor than

diffusion through building materials. Following the assumption that air moves more moisture

vapor than diffijsion, the subject of air transported moisture vapor remains the greatest enemy of

the wall system in our residences. The principle of restricting air-transported moisture has

created the need to concentrate on quality control in residential construction. The most effective

means to prevent or retard the flow of air through a wall system is to ensure that when the wall is

constructed that the air barrier and all penetrations through the wall (such as vents, inlets, and

outlets) are correctly and carefully detailed and installed to minimize the harmful effects of air

movement within the wall system.

Moisture dissipation from within a wall is directly related to Irath air movement and vapor diffusion

through the structure's wall assembly materials (Carll, 2000). The rampant use of vapor baniers

in residential construction has in many instances created redundant vapor barriers within the wall

cavity that may trap moisture and water. Even if the vapor barrier is not redundant, the vapor

barrier's placement is oftentimes in the wrong location creating as many problems as

redundancy. A vapor barrier's location should be carefully designed and specifically applied in

relation to the wall design, climatic conditions, and the wall's directional orientation (North, South,

East, or West). In order to more effectively control moisture, designers and builders must look

holistically at the indoor and outdoor atmospheric conditions of the building system design to

create the appropriate foundation, walls, and roof sections for the building assembly (Caril, 2000).

The recommended placement of a vapor barrier should not be universal. When determining

whether or not to use a vapor barrier, the specific application should be studied, designed, and

incorporated.

It should be noted that the term vapor barrier, as used in this paper, has been referred to as a

vapor diffusion retarder, vapor retarder, and vapor diffuser in the surveyed literature. The term

used on the job site to describe any of these materials is vapor barrier. For simplicity and

consistency within this paper and utilizing the language used on the job site, all future references

to any of these terms (vapor barriers, vapor diffusion retarders, vapor retarders, and vapor

diffusers) will simply be refen-ed to as vapor barriers.

A vapor barrier's performance is measured in perms, which is "the passage of one grain of water

vapor per hour through one cubic foot of material at a pressure differential of one inch of mercury

between the two sides of the material" (Allen, 1990). A vapor barrier is any material that has a

permeance of less than or equal to 1 in residential construction, but this number is typically much

lower for other types of construction (ASTM, 1999; Lstiburek, 2000). Materials that are

intentionally utilized as vapor barriers commonly have a perm rating of .1 or less, even though the

definition provides for less stringent permeance characteristics (DoE, 2002). To further prevent

any trapping of moisture in the wall cavity, the cold side of the material should have a perm rating

at least five times greater than the value at the warm side (DoE, 2002). A vapor barrier is not a

waterproofing application; it is a material with a low permeance that aims to slow or retard the

movement of vapor through the material to prevent the vapor from reaching the dew point on the

next cold surface (Bordenaro, 1991; DoE, 2002; Kubal, 2000; ASTM, 1999; Quiroutte, 1991; DoE,

2002; Straube, 2002; Lstiburek and Carmody, 1991; ICAA, 2002). The vapor barrier should

ideally be placed so that it is the next cold surface once the dew point has been reached within

the wall cavity. A vapor barrier should be included in the wall system design when the designer is

seeking to create a moisture and infiltration tight environment for the wall system (Stein and

Reynolds, 1992; Lstiburek, 2000). The correct incorporation of a vapor barrier in the wall system

can be looked at as a means of helping control condensation in wall assemblies.

The function of an air barrier is to stop outside air from infiltrating the building system materials

through the walls, windows, or roof and to keep inside air from exfiltrating through the building

envelope to the outside (Quiroutte, 1991). An air barrier may be utilized at any location within the

wall assembly and must be specifically designed, detailed, constructed and in order to ensure

that it is effective (Rousseau, 1990). Since air leakage is the most significant mechanism to be

considered in moisture control, air leakage should be controlled regardless of climate. It should

be remembered that air leakage moves far more moisture than vapor diffusion does through

materials (Sherwood and Moody, 1989 and Letter, 2000). A key principle to be remembered with

an air barrier is that they should be used everywhere, and they should be properly designed and

subsequently constructed (Straube, 2002). The air and vapor barrier information in Table 1 is a

source for definitions and a list of sample materials.

Air that leaks into a wall assembly must also have a means to exit the assembly. In most cases,

air leakage can be corrected through careful detailing and maintaining quality control at the inlet

and outlet opening sources of air leakage into wall assemblies (Lstiburek and Carmody, 1991).

Inlet openings are typically unsealed electrical outlet boxes, bottom edges of interior gypsum

board cladding, or openings/gaps/joints in interior air barrier systems. Outlet openings are joints

between sheets of exterior sheathings, top plate and bottom plate connections to the exterior

sheathings, service penetrations, and other construction flaws. These openings must be detailed

and constructed correctly if the air bam'er's integrity is to be maintained.

Table 1 - Vapor Barriers vs. Air Barriers, Definitions and Sample Materials Definition Sample Materials

VDRA/apor barrier

1. "The control of water vapor diffusion to reduce the occurrence or intensity of condensation" (Straube, 2001) that is driven by diffusion, and 2. May have imperfections and small cracks in its surfeice without greatly impairing the perfbmance of the penneable vapor barrier (Straube, 2001), or 3. Defined by building codes as anything with a permeability of 1 perm or less (Lstiburek, 2000)

- Polyethylene sheet membrane (Visquene) or film (varying throknesses, 2-6 mil and in 3-20 foot rolls) sealed with manufocturer recommended caulk, sealants, and tapes -EPDM - Plastic sheeting - Rubber membranes -Glass - Aluminum foil - Sheet metal - Oil-based paint - Bitumen or wax impregnated krafl paper - V\^ll coverings and adhesives - Foil-faced insulating and non-insulating sheathings - Vapor retarder latex paint - 2 coats of acrylic latex paint top coating mth premium latex primer -3 coats of latex paint - Scrim (open-weave fabric like fiberglass fabric) - Hot, asphaltk: rubberized membranes - Some insulations (elastomeric foam, cellular glass, foil faced isofoam) if sealed - Aluminum or paper faced fiberglass roll insulation - Foil backed wall board - Rigid insulatfon or foam-board insulation - 1/4 inch Douglas fir plywood with exterior glue - High-performance cross-laminated polyethylene

(Infonnation from Lstiburek, 2000; ICAA, 2002; Spence, 1998; Bordenaro, 1991; Maness, 1991; Lotz, 1998; Lstiburek and Carmody, 1991; Forest Products Lab, 1949; DoE, 2002)

Air Barrier/ Pressure Threshold

1. "Control airflow and thereby control convection vapor transporf (Straube, 2001), 2. Controls the moisture that is transported along with this airltow (Straube - vapor, 2002); 3. Helps to increase comfort, reduce energy consumption, help control odor, and help reduce sound transmission (Straube, 2001); and 4. Must be "continuous, durable, stiff (or restrained), strong, and air impemieable (Straube, 2001) 5. The point where the air pressure drop occurs within the cavity (Lstiburek, 2000)

- Unpainted gypsum board (sealed) - House-wrap, if property sealed and continuous - Continuous building paper (151b or 301b felt paper) - Plywood sheathing if joints property sealed - Foam board insulatton - Hot, asphaltic rubberized membranes - Some insulations (elastomeric foam, cellular glass, foil faced isofoam) if sealed

(Information from ICAA, 2002; DoE, 2002)

Air leakage through a wall assembly nearly approaches zero in modem construction because of

the rampant use of sealers and caulks between any and all the joints and materials (Straube,

2002). While the approach specified by most designers today calls for the use of housewrap as

the air barrier, they should be cautioned since this material has been shown in the DOE (2000),

Holladay and Vara (2000), McDaniel (2000), Holladay (2000), Cushman (1997), and James

(2000) articles to allow air, and subsequently moisture, to pass through once it has been stapled

or attached by other means. While all the joints may be taped, as directed by the housewrap

manufacturer, tapes and sealants are prone to deterioration over time. The importance has been

mentioned since housewrap is a frequently used component that must be considered and

designed when dealing with moisture. A full discussion of housewrap will not be discussed in this

paper.

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Air barriers often adt like vapor barriers due to the permeance of the materials used (Straube,

2002). The designer should consider whether or not the air barrier material qualifies as a vapor

barrier because utilizing a redundant system will often lead to harmful moisture issues within the

wall cavity by trapping vapor and creating an ideal environment for rot, decay, mold, and fungi to

flourish in (Roger, 1^4). Examples of easily incorporated inadvertent vapor barriers include vinyl

wall coverings and multiple coats of paint (i.e., 3 coats of latex paint) that inhibit the wall's

capacity to dry (Lstiburek, 2000). The inadvertent use of air barriers that behave like vapor

barriers contribute to the problems within our structures.

As a building is renovated and repaired, redundancy and inadvertent vapor barriers are often

created. For example, a common manner in which an Inadvertent vapor barrier is created in a

residence is when the occupants repaint a room. The structure's wall, when constructed, may

have a primer coat on the gypsum wallboard and two additional coats of non-vapor retarding latex

paint. When the occupants repaint their walls to update their home with two new of coats of latex

paint, they have unintentionally created a vapor barrier on the interior side of the wall. The

inclusion of this vapor barrier either creates a vapor barrier where none previously existed or has

now created a redundant vapor barrier because of one that was intentionally installed during

construction. Unintentional vapor barriers are frequently incorporated into buildings and should

be avoided when possible. Caution should be taken when renovating or updating

residences/structures to prevent redundancy.

The predominate approach to climate zone definition has segregated the United States into

climatic zones or areas according to the number of heating degree-days that the specific location

experiences throughout the year. The climatic zones used in this paper follow these principles:

• Heating climate is defined as an area that has 4000+ heating degree-days (Lstiburek

andCarmody, 1991).

• Mixed climate is an area that has up to 4000 heating degree-days (Lstiburek and

Carmody, 1991).

• Cooling climate is defined as an area that has 67°F or higher WB temperatures for

3000+ hours during the warmest 6 consecutive months and/or 73°F or higher WB

temp for 1500+ hours during the warmest 6 consecutive months (Lstiburek and

Carmody, 1991).

The information in Table 2 lists the approximate locations, but the specifics should be confirmed

for each locale prior to any design. Specific climatic information may be gathered fi-om ASHRAE,

the National Weather Service Bureau, or other relevant sources.

10

Table 2, States in the various climatic zones of the United States adapted from the graphical depiction of climatic zones from Lstiburek and Carmody (1991)

Heating Climate Maine, New Hampshire, Vemwnt, New York, Massachusetts, Connecticut, Rhode Island, New Jersey, Pennsylvania, West Virginia, Ohio, Michigan, Indiana, Illinois, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas, Colorado, Wyoming, Montana, Idaho, Utah, Nevada, Washington, Oregon, the northern half of California (roughly from San Francisco north), and Alaska

Mixed Climate Delavrare, Maryland, Virginia, North Carolina, Kentucky, Tennessee, Arkansas, Oklahoma, northern 2/3 of Texas (roughly area north of El Paso, San Antonio, and Beaumont), New Mexico, Arizona, and southern half of Califomia

Cooling Climate South Carolina, Georgia, Ftorida, Alat>ama, Mississippi, Louisiana, southern 1/3 of Texas, and Hawaii

Summary of Lessons Learned from the Review of Literature The following points have been adapted from a review of literature:

1. In a cold climate, a vapor barrier should be Installed close to the interior (warm) side of

the insulation.

2. in a hot, humid, tropical climate a vapor bamer should be placed on exterior (warm) side

of the insulation, if one is used.

3. In mild, more temperate climates a vapor barrier may or may not be necessary

depending upon the specific wall materials. For example,

a. The brick veneer and spruce siding wall may have a vapor barrier installed on the

exterior side of the insulation. It is recommended that no vapor bamer be

included because the vapor diffusion difference is not too different when

comparing a vapor barrier wall to the same wall without a vapor barrier. The

added expense of a vapor bamer should dictate not including one in this design.

The effective incorporation of proper ventilation and clear weep holes within this

wall cavity design is necessary because once water penetrates the cavity a

means to exit and a means to dry should exist.

b. The use of a plaster veneer wall should be avoided in this climate. This exterior

wall system's components (Durarok® and plywood) behave like a vapor retarder

for diffusion through the wall system and as such should be avoided to avoid

potential redundancy. However, if this wall system is utilized in this climate

proper ventilation and clear weep holes within this wall cavity design is necessary

to allow water to exit the cavity or to dry.

4. A vapor barrier should only be used if needed, and the use should be based upon the

specific wall system design, climate and orientation (North, South, East, or West) of the

structure's location and specific wall design.

5. A vapor barrier in a basement should be implemented in the same manner and location

as it was in the above-grade wall system.

6. A vapor barrier performs as a ground cover below the slab-on-grade and in crawl spaces

and shouki always be used. The vapor banier's inclusion in these locations helps reduce

11

moisture transport through capillary movement/suction from the soil up and into the

structure's materials.

7. The vapor barrier does not have to be airtight, but should be installed with as few

imperfections as possible to prevent the flow of air and vapor into the envelope. A rule of

thumb when installing vapor barriers is "a vapor barrier that covers 90% of the surface is

90% effecfive' (JLC Staff, 1993).

8. Common wall cover applications act as vapor barriers (i.e., 3+ coats of non-vapor

retarding latex paint and vinyl wall covering wallpaper).

9. The building's wall cavity should not be ventilated in hot, humid (cooling) climates.

10. The building's wall cavity should be ventilated in temperate and cold (heating) climates.

11. An air barrier is needed and should be designed into all structures, regardless of climate.

12. Air moves far more moisture than diffusion through materials.

13. Care should be taken when installing an air barrier because the air banier is onjy as

fundional as the air bamer's material integrity (i.e., be free of cuts, tears, punctures, rips).

14. Ventilation requirements in the attic space or crawl space should not be reduced with the

inclusion of a vapor barrier.

WUFI - Student Version, a transient heat and moisture transport computer wall modeling

program, was used to model vapor diffusion through several common wall assemblies (WUFI,

2003). The effects of air transported vapor remains the primary factor in determining whether or

not to utilize a vapor barrier in the construction of a wall system. The results from the WUFI test

runs have been summarized below with the assumption that vapor diffusion through the wall

system materials is the only driving force within the wall:

1. A vapor barrier [s necessary on the outside of the insulation in cooling climates to combat

the effects of vapor diffusion.

2. A vapor barrier js necessary on the inside of the insulation in heating climates to combat

the effects of vapor diffusion.

3. A vapor barrier is not necessary in mixed climates to address vapor diffusion through the

wall system.

The effect of air movement through building materials remains the primary issue to be addressed

in building system design and construction. The air barrier should be installed with no

penetrations, cuts, tears, or unsealed openings. The air barrier's integrity is critical if the wall

components are to be kept dry and not subjected to the harmful effects associated with moisture

penetration due to air movement. The air barrier's integrity should be checked prior to the

installation of subsequent building assembly layers. The vapor barrier's integrity, on the other

hand, does not have to be as perfect if the air barrier has been installed correctly. If the vapor

12

barrier only has to combat the effects of vapor diffusion through the materials, rather than the

effects of air movement and vapor diffusion, then a vapor barrier with a few minor blemishes will

perform its role correctly and efficiently. If the vapor barrier is to fulfill the dual role of vapor and

air barrier then the rules for installing an air barrier apply.

The quality assurance (QA) and quality control (QC) processes are critical during the construction

of the air barrier and the sub-slab ground cover vapor barrier. These barriers should be installed

as imperviously as possible and their integrity should be carefully checked prior to subsequent

work being placed on top of their respective surfaces. The effectiveness of the wall system air

barriers and the sul)-slab ground cover vapor barriers are only as effective as they are continuous

(JLC Staff Report, 1993). Any and all penetrations should be patched or sealed. QA/QC

procedures during construction of these barriers are vital to the success of the wall assembly in

the building as it combats moisture.

The directional orientation that the wall faces plays a significant role in the determination of

whether or not to include a vapor barrier within the wall. The directional orientation of south and

west facing structure walls will require different design parameters than walls facing north and

east. The south and west facing walls face more effects from themnal mass and heat gain due to

their particular directional orientation. These walls can be expected to maintain higher

temperature readings than those on the north and east facing walls throughout the year and the

dew point temperatures, and possibly the dew point location, within the wall may vary significantly

compared to the same wall on the east or north face of the structure. The specific dew point

locations vnthin the wall system should be calculated for each structure's wall when designing the

residences wall systems.

Vapor barrier standards defined by ASTiVI The ASTM standards, C755, define the vapor barrier's primary function within the wall system as

1o control the movement of diffusing water vapor into or through a permeable insulation system"

(ASTM, 1999). The diffused movement of vapor into and through a wall system follows one of

two flow patterns, unidirectional or reversible (ASTM, 1999). Vapor pressure difference is the

driving factor in determining how vapor barriers are to be used since the greater the pressure

differential, the greater the rate of diffusion through the assembly (ASTM, 1999). During the

design phase, the expected pressure differences should be realistic, not estimated, when

determining the vapor banier requirements (ASTM, 1999).

ASTM defines unidirectional flow, as having a "water vapor pressure difference [that] is

consistently higher on one side of the system than the other" (ASTM, 1999). In cooler climates,

13

this unidirectional vapor flow should include the design of the vapor bamer on the indoor, warmer,

side of the wall insulation.

Reversible flow is defined as having a "vapor pressure [that] may be higher on either side of the

system, and it often changes with the seasons" (ASTM, 1999). Design for reversible flow

conditions do not greatly influence where in the wall system the vapor bamer should be placed.

The assumption made with reversible flow is that drying will occur during the opposite season for

which the barrier was placed within the cavity.

If a membrane retarder material is to be used within the cavity, ASTM recommends using a

retarder with a lower permeance if a five-foot (1.5 meter) wide roll is used, or using a vapor

barrier/retarder with a higher permeance if a 20 foot (6.1 meter) width is installed (ASTM, 1999).

The reason for the permeance difference, dependent upon the width of the roll, is due to the air

penetration through the materials. The smaller width roll of membrane retarder would require a

lower permeance because there would be more laps, joints, and seams than the wider roll and

thus more air entrained vapor would potentially be allowed to pass through the openings. Even

with proper sealing of the laps, joints, and seams of the smaller width rolls, perfect construction

quality should never be relied upon for installation, especially since sealants are prone to

breakdown over time and the quality of installation cannot be relied upon to be "as

recommended" by the manufacturer (which most design specifications indicate). When designing

the cavity, low permeability insulation installed with sealed, vapor tight joints often acts like a

vapor barrier within the wall. A redundant vapor barrier system should be avoided, but is often

inadvertentiy constructed into the wall system design when a vapor banier is purposefully used in

conjunction with low permeability insulation.

The ASTM standards also recommend the implementation of an air banier system within the wall

cavity (ASTM, 1999). The potential for condensation should be investigated when designing the

placement of the air barrier within the wall system (ASTM, 1999). The recommended placement

of the air banier within the cavity is on the warm side of the insulation and should be installed in a

continuous, unbroken manner to prevent the uncontrolled movement of air through the wall

system, as previously discussed.

The ASTM has defined two recommended vapor barrier design principles called flow-through

design and moisture storage. Flow-through design is supposed to eliminate the possibility of

condensation within the insulation and should include the use of a highly permeable insulation

within the cavity (ASTM, 1999). The purpose of the high permeability insulation is to allow vapor

to flow through the insulation and condense, if the vapor is to condense, on the next lower

14

permeable surface (ideally the vapor isarrler) within the system where the liquid would either be

drained or removed through ventilation. The moisture storage principle allows for some moisture

accumulation within the system's insulation, but the rate of accumulation is small and low

permeability insulation should be used (ASTM, 1999). The design utilizing the moisture storage

principle assumes that moisture condensation quantities will not exceed the storage

characteristics of the material before the moisture is removed from within the system.

The vapor pressure differentials in summer tend to cause vapor to flow in an inward direction, and

as such, a vapor barrier should be used on the outer side of the insulation facing the exterior

covering of the structure (ASTM, 1999). The ASTM guidance goes on to state "the vapor retarder

should still be located on the side of the insulation facing the interior of the building to control

vapor flow under the more severe conditions" (from the warm winter side of the system) (ASTM,

1999). The guidance continues, stating that if an impermeable insulation material is utilized, a

separate vapor banier is not needed at all as long as the "joints (if any) are made impermeable by

suitable sealing methods" as recommended by the manufacturer (ASTM, 1999). The wall system

must be designed for moisture that penetrates the retarder, moves into the insulation, and finally

continues on to the outside through some means of ventilation or forced air movement within the

cavity (ASTM, 1999). The ASTM standards provide design solutions/recommendations to

effectively handle all climatic conditions encountered in the United States construction process,

and they provide designers and builders with a clear understanding of how to correctly utilize

these materials in the wall systems.

CABO and ICC Code Summaries The current residential building codes, as published by the Council of American Building Officials

(CABO) and the International Code Councils (ICC), have been investigated with regards to the

implementation of vapor barriers for residential one and two family dwellings. The applicable

code sections from these references have been tabularized in summary fomri in Table 3 below.

Table 3, Vapor barrier specific code summaries, adapted from CABO (1995) & ICC (2000)

Section Code Title Discussion 321 CABO "Moisture Vapor Retarders" - Required in all iianne walls and floors, and ceilings, not

ventilated to allow moisture to escape. - Vapor larrier to be used on warm-in-winter side of thermal insulation with two (2) exceptions:

1.) Where moisture or its freezing will not damage the materials.

2.) Hot, humid climates: 67°F+ wet bulb temps for 3000+ hours or yS'F* wet bulb temp for 1500+ hours during warmest six (6) consecutive months of year.

15

Sectron Code Title Discussion

R322 ICC - In all framed vralls, floors and roofs/ceilings comprising elements of building thermal envelope. - A vapor barrier shall be installed on warm-in-winter side of insulation with three (3) exceptions:


2.) Hot, humid climates: 67°F+ wet bulb temps for 3000+ hours or 73°F+ wet bulb temp for 1500+ hours during vrarmest six (6) consecutive months of year.

3.) Counties listed in ICC Table 1101.2, p.72-80 (summarized In report's table 2).

406 CABO "Foundation Waterproofing and Dampproofjng"

- No discussion other than waterproofing applications and moisture banier installation R406 ICC

409 CABO "Crawl Space" - When ground surfece is treated with a vapor banier, ventilation opening requirements may be reduced to 1/1,500 of the under- floor area, or - Ventilation openings may be omitted when continuously operating mechanical ventilation is provided at a rate of 1.0 cftn for each 50 ft^ of crawl space and the ground surface covered with a vapor barrier.

R408 ICC "Under-Ftoor Space" - Same two rules/exceptions as CABO, plus - Ventilation openings not required if ground covered with a vapor banier, space is supplied with conditioned air, and perimeter walls are insulated.

505 CABO "Concrete Floors (on ground)"

- Vapor barrier with Joints lapped at least six inches (6") shall be placed between slab and base course or prepared subgrade if no base course exists - Three (3) exceptions:

1.) Detached structures that are to be unheated (i.e., garages).

2.) Flatwori< not likely to be enclosed and heated later (i e., sidewalks, patios).

3.) As approved by building official. R506 ICC Exact words and requirements described in CABO

806 CABO "Roof Ventilation' Net free cross-ventilation area may be reduced to 1 to 300 with installation of vapor barrier (material with a transmission rate not exceedinq 1 perm) installed on the warm side of ceiling.

R806 ICC Exact words and requirements described in CABO It should be noted that t>oth CABO and the ICC state, with identical language, that "the total net free ventilating area shall not be less than 1 to 150 of the area of space ventilated except that the total area is permitted to be reduced to 1 to 300, provided at least 50% and not more than 80% of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 ft. above the eave or comice vents with the balance of the required ventilation provided by eave or comice vents." 907 CABO "Built-up Roofing" - Vapor banier to be installed between deck and insulation where

average January temperature is below 45°F, or - Where excessive moisture conditions anticipated within the building.

R907 ICC - Nothing vapor larrier specific

The information that is presented in Table 4 has

been adapted and condensed from the ICC,

Section R322, Table 1101.2, pages 72-80. The

exact counties/parishes listed should be

referenced when designing or constructing a

structure in these states, and an exemption is

being sought for moisture vapor barrier inclusion

on the warm in winter side of the insulation.

Table 4, Adapted from information from ICC (2000): Section R322, Exception 3

state Number of counties exempted from warm-in-winter V.R. installation

North Carolina 16 of 100 counties South Carolina 30 of 46 counties

Georgia 109 of 159 counties Florida All counties

Alabama 47 of 67 counties Mississippi 64 of 82 counties

Louisiana All parishes Arkansas 44 of 75 counties

Tennessee 2 of 95 counties

Oklahoma 6 of 78 counties Texas 139 of 254 counties

16

The two codes have similar intended audiences (one and two fanrfliy dwelling designers and

builders), and the requirements with regards to vapor barriers are nearly identical in both

language and verbiage. Both of the codes dictate to the designer or builder where the vapor

barriers will be placed with the exception of the section on concrete floors (on ground) where the

provision, "or as approved by building official" is included.

The requirements, as outlined in the codes, are fairly specific with regards of where, when, and

how to install vapor barriers within the wall systems. The code requirements do not easily allow

proposals for acceptable alternatives by designers and builders who may be implementing

altemative approaches to construction.

Detail Specifics for Foundations, Walls, and Roofs Foundations The foundation vapor barrier design is straightforward and consistent for heating, cooling, and

mixed climates. A vapor barrier should be included in all climates as a ground cover under slab-

on-grade and in crawl spaces. The accumulation of moisture through the foundation/support

elements (slab, basement, crawl space, etc.) is the primary point of entry into residential

construction assemblies (Suprenant, 1994). The incorporation of vapor barriers in the foundation

design is only going to be as effective as the drainage mechanisms facilitate. Designing proper

drainage includes not only collecting the water, but also effectively moving the water out and

away from the structure so that the water does not accumulate and then migrate back up and into

the wall system. Two typical design details for the slab-on-grade and a crawl space may be

seen in Figures 1 and 2.

The placement of the sub-slab vapor barrier will perform a dual role in the structure's moisture

protection. The first role is to break capillary movement of moisture upward and into the

structure's assembly (Lstiburek and Camriody, 1991). The role of the sub-slab vapor barrier is to

break capillarity, and provide the building with its first preventative measure in dealing with

moisture by minimizing the potentially harmful effects within the structure. Special care should be

taken to ensure that the vapor barrier's integrity is maintained since it is also fulfilling the role of

an air barrier.

17

The second role of the sub-slab vapor barrier is to help prevent moisture migration through the

porous concrete (Suprenant, 1994). The vapor barrier material for this application may include

sheet polyethylene, damproofing material, multiple layers of roofing paper, or EPDM sheeting. All

joints should be lapped at least six inches, and the vapor barrier material should be as impervious

as possible to any

j. p6|tjTie«TS3 ptwtJ Pipe

breaks, punctures, or

other such penetrations

(Suprenant, 1994). The

role of the vapor barrier

in this particular

application should be

designed and

constructed in a similar

manner as an air barrier

within the wall system.

The vapor barrier should be placed on top of, and in direct contact with, the compacted subgrade

material. Then, on top of the vapor barrier and below the concrete slab, a three-inch thick layer of

sand or varied sizes of

Figure 1, Adapted standard slab-on-grade and basement detail from Ramsey and Sleeper (1992).

—vw*-fe;gs^

^ ii«Di>"rt<tJ

pSCP8aJGD**NT

;. CMEec <SR«i/teu t)B*iM«6e RFC

gravel should be applied

and lightly compacted

(Suprenant, 1994).

Gravel is recommended

over sand because gravel

is less easily displaced

during the placement of

the concrete slab and

provides a consistently

more uniform surface for

the slab's placement

(Suprenant, 1994). A

discussion with a

residential house builder

stated that this sand or gravel layer is seldom incorporated because of the significant cost and the

perceived benefits of incorporation do not outweigh the increased cost of installation (Vinson,

2003). Special care and oversight should be taken during tiie concrete placement phase since

the vapor barrier's effectiveness is proportional to the integrity of the banier membrane below

(JLC Staff, 1993).

■i.vviv ^■' Figure 2, Adapted standard crawl-space detail from FPL

(1949) and Ramsey and Sleeper (1992).

18

The requirements, as outlined in the CABO and ICC codes, make recommendations for the

incorporation of vapor barriers in the on-grade, sub-slab section that are in line and follow the

recommendations and guidance discovered during a review of literature not presented here.

Walls The climate where the residence wall is to be located, in conjunction with the composition of the

wall components, strictly define how, where, and if a vapor barrier should be included in the

design. As previously discussed, the directional orientation of the wall system also plays a

significant role in determining when to place a vapor barrier within the wall system. The internal

wall temperatures vary significantly depending on if the wall is exposed to climatic conditions on

the north, south, east or west sides of the structure. The wall assembly temperatures and

thermal mass effects are greatly impacted by the directional orientation. The examples selected

do not represent all known housing solutions, merely the most popularly used solutions in the

residential construction industry today.

In a heating climate, a vapor barrier should be installed on the warm side of the insulation in both

the spruce siding model and the brick veneer models. The type of vapor barrier recommended in

this climate is the polyethylene sheet membrane. The use of the plaster-like exterior material, in

conjunction with Durarok® and plywood, should be avoided in this climate because of

redundancy since a vapor barrier is necessary on the warm side of the insulation in this climate.

The plaster wall system's component composition (Durarok® and plywood) on the interior of the

plaster coat behaves like a vapor barrier for vapor diffusion through the wall system. It is

recommended that this assembly be avoided in mixed and heating climates because of the great

potential for vapor barrier redundancy.

In a cooling climate, a vapor banier should be installed on the exterior side of the insulation. A

"Smart Vapor Banier", or bitumen or wax impregnated krafl paper, is recommended instead of a

polyethylene sheet membrane in this climate. It should be noted that clear weep holes and

proper ventilation should be utilized if a plaster-like exterior surface is selected.

In a mixed climate, a vapor barrier is not recommended. If a vapor barrier used then it should be

installed at the same location within the wall as that for a cooling climate. It should be noted that

a vapor barrier is not recommended because of the added cost and high probability of

redundancy. If a vapor barrier is used, then install it like in cooling climate structure discussed

earlier. The plaster-like exterior wall system, in conjunction with Durarok® and plywood, already

behaves like a vapor barrier and a separate vapor barrier should not be installed. However, if this

19

wall system Is utilized in the mixed climate strict adherence to proper ventilation and clear weep

holes within this wall cavity design are necessary to allow water to exit the cavity or to dry.

The effects of the redundancy (for example, as caused by multiple layers of latex paint) in a

cooling climate's structure are expected to be worse than those in the heating climate. The

placement of the intentional vapor banier on the exterior side of the insulation in a cooling climate

and the inclusion of the inadvertent vapor barrier on the interior side of the gypsum board will

create a potential vapor trap in the insulation and gypsum board components of the cooling

climate's wall assembly. The effect of redundancy caused by paint in the heating climate, with an

intentional vapor barrier on the interior warm side of the insulation, creates a vapor trap inside of

the gypsum board. It may be concluded that the effects of vapor accumulation will be significantly

minimized in the heating climate when compared to the cooling climate's wall.

Proper ventilation and dear weep holes in the wall cavity must exist because once water enters

the cavity it should have botii a means to exit and a means to dry. If the water is not allowed to

exit once it enters the cavity, the water will seek equilibrium within the space and migrate across

and through other materials. In this climate, the spruce siding wall assembly has the same

recommendations as those for the brick veneer wall. A plaster veneer wall should be avoided in

this climate.

Table 5 has been developed as a synopsis or guide for use when making design decisions with

regard to the common wall systems in use in residential housing today.

Roofe The use of a vapor barrier in the roof/ceiling components of the assembly is effective and

recommended as a means of being able to reduce the ventilation requirements in this part of the

assembly according to the codes. The specifics of utilizing, or not utilizing, a vapor barrier in this

area of the assembly is dependent upon the climatic area of the structure, the design of the

ceiling/roofing connection, and whether or not the roof is ventilated. All of these items must be

considered in conjunction with one another and cannot be looked at or designed in isolation when

making a determination for when to utilize a vapor banier.

A great deal of debate is present in the literature that has been reviewed, and no firm consensus

has been reached across all the material reviewed with regards to vapor barriers in the roof

system. The only firm conclusion with regards to the inclusion or exclusion of vapor barriers in

the roof design is to calculate the specific point where the dew point is reached within the roof

system and place the vapor barrier on the next cold surface. The infiuence of air movement must

be considered, as well as the potential for drying through air movement to the interior or exterior

20

of the roofing system materials. The designer must also be cognizant of the fact that if a vapor

barrier is included and the roof develops a leak, the vapor barrier could behave as a vapor trap

and cause the system to retain the water by not allowing it to escape. Table 6 has been

developed as a synopsis or guide for use when making design decisions with regard to various

roofing systems.

Conclusions In conclusion, builders ridicule the literature and construct out of experience and not what either

the literature or wall analysis calculations reveal. The different climate summaries and opinions of

the authors are as follows:

1. Heating Climate: Vapor barriers should be used in heating climates at all locations within

the structure's foundation, wall, and roof assemblies.

2. Cooling Climate: The implementation of a vapor barrier should be included within the

foundation and wail assemblies of all structures in a cooling climate, but the specific

application in the roof remains one area that depends upon the specific, detailed structure

design.

3. Mixed Climate: A vapor barrier is recommended for the foundation and roof assembly for

all structures in the mixed climate, but the when and where to utilize one within the wall

system remains less clear and is not recommended. The principles of flow-through design

are to be utilized in this climatic area according to the literature reviewed. The flow of air

through the wall is the primary driving agent of moisture into and out of the wall assembly

depending upon what season the structure is in currently. The principle of flow-through

design should be adhered to since it allows wetting during one season and drying during the

opposite so that moisture within the cavity attains equilibrium across the wall section during

the course of the year.

References Cited Allen, E. (1990). Fundamentals of Building Construction: Materials and Methods, 2nd Edition.

John Wiley and Sons, Inc.; New York; 803 p.

American Society ofTesting and Materials (ASTM). (1999). ASTM Standards in Building Codes. Volume 2: Designation C 755 - 97. ASTM; West Conshohocken PA; 1994 p.

Bordenaro, M. (1991). "Vapor Retarders Put Damper on Wet Insulation." Building Design and Constmction. 32(9), 74-77.

Carll, C. (2000). 'Rainwater Intrusion in Light-Frame Building Walls." From Proceedings of the 2nd Annual Conference on Durability and Disaster Mitigation in Wood-Frame Housing: November 6-8, 2000, Madison Wl, fl'om www.toolbase.org, accessed 3 Jun 03.

Council of American Building Officials. (1995). CABO: One and Two Family Dwelling Code, 1995 Edition, Fourth Printing. CABO; Falls Church VA; 350 p.

21

Department of Energy. (2002). "Vapor Diffusion Retarders and Air Barriers." Consumer Energy Information: EREC Reference Briefs obtained from www.eere.enerav.qov/consumerinfo/rfbriefe/bd4.html, accessed on 28 IVIay 03.

Insulation Contractors Association of America (ICAA). (2002). "Technical Bulletin: Use of Vapor Retarders." ICAP; Alexandria VA. Obtained from www.toolbase.orq, accessed 3 Jun 03.

International Code Council. (2000). Intemational Residential Code: For One and Two Familv Dwellinas. International Code Council; Falls Church VA; 566 p.

JLC Staff Report. (1993). "The Last Word (We Hope) on Vapor Barriers: Answers to the most common questions about moisture migration through walls and ceilings." Journal of Light Construction, 11(11), 13-17.

Kubal, M. (2000). Construction Waterproofing Handbook. McGraw-Hill Handbooks; New York.

Letter and response in "On the House". (2000). "Ceiling Vapor Barrier-Yes or No?" Journal of Light Construction, 18(5), 21,23,24.

Lotz, W. (1998). "Specifying Vapor Barriers." Building Design and Construction, 39(11), 50-53.

Lstiburek, J. (2002). "Air Barriers vs. Vapor Barriers" from www.buildinascience.com/resources/walls/air barriers vs vapor barriers, accessed on 4 June 03.

Lstiburek, J. (2000). BuikJer's Guide to Mixed Climates: Details for Desian and Construction. The Tauton Press; Newton CT; 328 p.

Lstiburek, J. and Camnody, J. (1994). "Moisture Control for New Residential Construction" in Moisture Control in Buildinas. ASTM Manual Series: MNL 18; Philadelphia, PA; 321-347.

Lstiburek, J. and Camriody, J. (1991). Moisture Control Handbook: New, low rise residential constmction. Oak Ridge National Laboratory; Oak Ridge TN; 247 p.

Maness, G. (1991). "Preventing Wall Deterioration." Journal of Property Management. 56(5), 33-38.

Quiroutte, R. (1991). "Air and Vapor Baniens." Progressive Architecture. 72(9), 45-51.

Ramsey, C and Sleeper, H. (1992). Construction Details from Architectural Graphic Standards. Eight Edition. ecSted by James Ambrose. New York, John Wiley & Sons, Inc.

Sherwood, G. and Moody, R. (1989). Light-Frame Wall and Floor Systems: Analysis and Perfomrtance. General Technical Report, FLP-GTR-59; U.S. Department of Agriculture, Forest Service, Forest Products Laboratory; Madison Wl; 162 p. Obtained from vtfww.nahbrc.ora, accessed 3 Jun 03.

Spence, W. (1998). Constmction Materials. Methods, and Technigues. Delmar Publications; NewYork;1195p.

Stein B. and Reynolds, J. (1992). Mechanical and Electrical Equipment for Buildinas: 8th Edition. John Wiley and Sons, Inc.; New York; 1627 p.

Straube, John F. (2002). "Moisture in the Buildings." ASHRAE Journal, January 2002. httD://www.civil.uwaterloo.ca/beq/Downloads/ASHRAE%20Journal%20Jan%202002%20 Moisture.pdf, accessed on 31 Oct 02.

22

Suprenant, B. (1994). "Sub-Slab Vapor Barriers." Journal of Light Construction, M{8), 37-39.

Trechsel, H., Achenbach, P., and Launey, S. (1982). "Moisture Control in Building Wall Retrofit" in Moisture Migration in Buildings. ASTM STP 779; Philadelphia PA; 148-159.

U.S. Forest Service. (1949). Condensation Control: in dwelling construction by Forest Products Laboratory, Forest Service, U.S. Department of Agriculture in collaboration with the Housing and Home Finance Agency, Forest Products Laboratory; Madison Wl; 73 p.

Vinson, J. (2003). Telephone interview with Joe Vinson of Joe Vinson Builders (Mobile, Alabama) on 21 Aug 03.

Wetterman, T. (1982). "Control of Moisture Migration in Light Frame Walls" in Moisture Migration In Buildings. ASTM STP 779; Philadelphia PA; 102-109.

WUFI. (2003). WUFI: V\Srme-und Feuchteransport InstationSr (Transient Heat and Moisture Transport), Educational Software Program. Oak Ridge National Laboratory; Oak Ridge TN; obtained from www.ornl.qov/ORNL/BTC/moisture/. and accessed on 1 Sep 03.

23

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1.0 Literature Review for Vapor Barriers in Residential Construction Applications

26

1.1 Introduction The major problem cited by independent residential builders in new housing construction is

moisture related, primarily, due to rot, decay, and the growth of molds and fungi. Condensation

and moisture related problems were first recognized and investigated in a 1923 Forest Products

Laboratory survey of dwellings due to early exterior paint failure on residential houses (U.S.

Forest Service, 1949). It has more recently been reported, "with the exception of structural

errors, 90% of building construction problems are associated with water" and the harmful effects

related to its penetration into our structures (Trechsel, Achenbach, and Launey, 1982). Current

building codes and property standards also contribute because the methods being employed are

prescriptive rather than performance oriented and these codes have tried to create a universal

approach for construction rather than looking holistically at the wall assembly components

(Trechsel, Achenbach, and Launey, 1982 and Sherwood and Moody, 1989).

Several assumptions and limitations were been made in the course of the literature review, during

the code analysis, and the test data results interpretations. A major assumption that this report

espouses is that air moves far more moisture vapor that diffusion through materials. Following

the assumption that air moves more moisture vapor than diffusion, the subject of air carried

moisture vapor remains the greatest enemy of the wall system in our residences. The principle of

preventing air-transported moisture has created the need to concentrate on quality control in

residential construction. The most effective means to prevent or retard the flow of air through a

wall system is to ensure that when the wall is constructed that the air barrier and any penetrations

(such as vents, outlets, etc.) are correctly and carefully detailed and installed to minimize air

movement into the wall system. It is the opinion of the author that if careful and thorough

attention to these details is done that the effects of moisture vapor penetration in our wall systems

will be reduced.

It should be noted that the term vapor barrier has been referred to as a vapor diffusion retarder,

vapor retarder, and vapor diffuser in the literature surveyed. For simplicity and consistency within

this report, all future references to any of these terms (vapor barriers, vapor diffusion retarders,

vapor retarders, and vapor diffusers) will simply be referred to as vapor barriers from this point

fonward.

The literature review has been broken down into six primary sections for initial investigation and

basic understanding of the role that vapor barriers play in dealing with moisture in residential

construction. The literature review will: 1.) Provide definitions to be utilized in the course of this

investigation, 2.) Explain what moisture is, 3.) Investigate how moisture is generated, 4.) Study

some means for dealing with the moisture transport mechanisms, 5.) Perform a comprehensive

review of why vapor barriers are used today, and 6.) Conclude with a review of the how to design

27

and implement vapor barriers in building assemblies (foundations, walls, and roofe/ceilings)

according to what has been published.

1.2 Keywords and Definitions The report has the following keywords: moisture, condensation, vapor barriers/vapor diffusion

retarders, and air t)arr1ers.

The following definitions will be used when referencing these terms in the discussion that follows

in the subsequent sections.

Adsorption The soaking in of moisture (Kubal, 2000), and The attraction of water vapor molecules close to solid molecules by complementary polar nature of solid molecules or the polarity induced in solid molecules by dispersion and induction effects (Straube, 1988)

Absorption The collection or condensation of moisture on the surface of a material (Kubal, 2000)

Air Barrier Any material that blocks the flow of air through a building system, or the point where the air pressure drop occurs within the cavity

Air 1 nfiltration/Transport

Movement of air through a wall system from an area of high pressure to an area of low pressure, this is typically a fast process (Krogstad and Weber, 1999) and (Lstiburek, 2000)

Condensation The moisture contained within air that is deposited in a liquid or solid state on a cool surface (Krogstad and Weber, 1999)

Dew Point (DP) 100% relative humidity, or the point when dew will form and water vapor will condense when saturated air touches the first surface that is at or below the air's dew point temperature (Stein and Reynolds, 1992), or "the temperature at which a specific atmosphere is saturated with water vapor" (ASTM, 1999), or the temperature at which a volume of air will become saturated, and below which condensation will occur (Krogstad and Weber, 1999)

Desorption "The action or process of releasing an absorbed substance from something" (Guralnik, 1982)

Dilution Ventilation Similar process to dehumidification (Lstiburek, 2000) Dry-Bulb Temperature (DB)

"Temperature of ambient mixture of air and water vapor measured in the normal way with a simple thermometer" (Stein and Reynolds, 1992)

Enthalpy "The sum of the sensible and latent heat content of an air-moisture mixture, relative to the sensible plus latent heat in air at 0°F at standard atmospheric pressure" (Stein and Reynolds, 1992)

Evaporation "A process in which something is changed from a liquid to a vapor without its temperature reaching the boiling poinf (Guralnik, 1982)

Humidity Ratio "The amount of moisture by weight within a given weight of air (Stein and Reynolds, 1992)

Pemn The unit of measure used to measure the passage of one grain of water vapor per hour through one cubic foot of material at a pressure differential of one inch of mercury between two sides of a material (Allen, 1990)

Relative Humidity (rh)

"Ratio of density of water vapor in air to maximum density of water vapor that such air could contain, at the same temperature, if it were saturated" (Stein and Reynolds, 1992)

Resistance The degree to which material restricts the flow of water vapor through it (O'Connor and Johnson, 1995)

Saturation Line The line on the psychrometric chart where the dew point is reached in a specific building system and condensation will occur

28

Splashback Water bouncing off the ground and splashing back onto the structure (Fisette, 1995)

Thermal Insulation System

"Thermal resistance to heat flow combined with means for attachment to the surface to be insulated, and with facings, vapor diffusion retarders, joint sealants, or protective coatings as installed." (ASTM, 1999)

Vapor Diffusion Process by which moisture moves from air with a higher dew point temperature to air with a lower dew point temperature seeking equilibrium, this is typically a slow process (Krogstad and Weber, 1999), or the movement of moisture in the vapor state through a material as a result of vapor pressure difference (from a area of high pressure to and area of low pressure or concentration gradient) and/or temperature difference (warm side of a material to cold side of a material or the thermal gradient) (Lstiburek, 2000)

Vapor Diffusion Retarder (VDR) or Vapor Bamer

"Those materials or systems which adequately retard the transmission of water vapor under specified conditions. (For practical purposes it is assumed that the permeance of an adequate retarder will not exceed 1 perm, although at present this value may be adequate only for residential construction. For certain other types of construction the permeance must be very low.)" (ASTM, 1999), or Any material that has a permeability of 1 perm or less (Lstiburek, 2000)

Water Leakage The water penetration of a wall system that causes damage (Krogstad and Weber, 1999)

Water Vapor Diffusion

"The process by which water vapor spreads or moves through permeable materials caused by a difference in water vapor pressure." (ASTM, 1999)

Water Vapor Permeability (Permeability)

"The water vapor transmission of a homogeneous material under unit vapor pressure difference between two specific surfaces, per unit thickness." (ASTM, 1999), or "the rate of water vapor transmission induced by a difference in vapor pressure through a certain area of material, per unit of thickness" (Holladay, 2000)

Water Vapor Pemeance (Permeance)

"The water vapor transmission of a material under unit vapor pressure difference between two specific surfaces." (ASTM, 1999), or the amount of water vapor diffusing through a material (O'Connor and Johnson, 1995), or "the rate of water vapor transmission induced by a difference in vapor pressure through a certain area of material" (Holladay, 2000)

Water Vapor Transmission

"The steady-state time rate of water vapor diffusion or flow through unit area of a material, normal to specific parallel surfaces under specific conditions of temperature and humidity at each surface. (ASTM, 1999), or "the rate at which a certain weight of water vapor passes through a certain area of a material, under certain test conditions" (Holladay, 2000)

Wet-Bulb Temperature (WB)

"Temperature shown by a thermometer with a wetted bulb rotated rapidly in the air to cause evaporation of its moisture" (Stein and Reynolds, 1992)

1.3 Review of Literature 1.3.1 What is moisture? Several underlying principles exist when trying to understand building systems and the capacity

of the system materials and design to carry, transport, and store water (regardless of its form).

The principles can best be summarized with the statement that "water is lazy, and it will always

chose the easiest path to travel" (Lstiburek, 2000). The purpose of this literature review will be to

gain an understanding of the basic principles of water in its moisture phase and then develop an

understanding of how moisture moves through building system materials.

29

The basic principles of moisture closely adhere to the second law of thermodynamics. The

second law deals with the natural flow of energy processes and can be summarized as; things

are constantly seeking a state of equilibrium and move from areas of more to areas of less.

Applying this principle to vapor pressure, areas of high vapor pressure move towards areas of low

vapor pressure and this can be correlated to movement from warm areas to cold areas (Stein and

Reynolds, 1992).

Webster's Dictionary has defined moisture as "water or other liquid causing a slight wetness or

dampness" (Guralnik, 1982). Moisture is all around us. Its presence is created with each activity

we perform, and it is in each material we use in the course of our daily lives.

■ It is present as a vapor in the air all around us (ASHRAE, 1972).

■ It is adsori3ed in the materials we use (ASHRAE, 1972).

• It can change forms from a vapor to a liquid to a solid depending upon the

temperature, pressure, and relative humidity levels (ASHRAE, 1972).

■ It desires as a vapor 1o move from high concentrations to low concentrations, or from

more to less" (Straube - moisture, 2002).

Moisture can be transported through four movement mechanisms: 1.) Liquid flow, 2.) Moisture

transport due to capillary suction, 3.) Air movement, and 4.) Vapor diffusion (Lstiburek and

Carmody, 1991 and Straube, 2002). Each of these mechanisms must be dealt with during the

design and construction of the structure's systems (foundation, walls, and roof) in order to

effectively respond to moisture (Lstiburek and Carmody, 1991). The moisture movement control

mechanisms must be specific and not generic with regards to what climatic region of the United

States the designer or builder (simply referred to as designer from this point forward) is designing

or planning. The design for moisture must be climatically specific since each climatic area of the

country dictates different details that are responsive to the different environmental conditions to

be experienced.

The predominate approach to climate zone definition appears to have segregated the United

States into climatic zones or areas according to the number of heating degree-days that the

specific location experiences throughout the year. Thus, each designer should analyze his or her

particular code and climate to determine how to address this subject. The climatic zones adapted

as the most common follow these principles:

• Heating climate is defined as an area that has 4000+ heating degree-days (Lstiburek

and Carmody, 1991).

• Mixed dimate is an area that has up to 4000 heating degree-days (Lstiburek and

Carmody, 1991).

30

• Cooling climate is defined as an area that lias 67°F or higher WB temperatures for



Carmody, 1991).

The specific locale's climatic information may be gathered and computed from ASHRAE, the

National Weather Service Bureau, or other relevant sources. Lstiburek and Carmody have

defined these areas using a map of the United States. The information in Table 1.1 lists the

approximate locations, but the specifics should be confinned for each locale prior to any design.

Table 1.1, States in the various climatic zones of the United States adapted from the graphical depiction of climatic zones from Lstiburek and Carmody (1991)

Heating Climate Maine, New Hampshire, Vermont, New York, Massactiusetts, Connecticut, Rhode Island, New Jersey, Pennsylvania, West Virginia, Ohio, Michigan, Indiana, Illinois, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas, Cotorado, Wyoming, Montana, Idaho, Utah, Nevada, V\feshington, Oregon, the northern half of California (roughly from San Francisco north), and Alaska

Mixed Climate Delaware, Maryland, Virginia, North Carolina, Kentucky, Tennessee, Arkansas, Oklahoma, northern 2/3 of Texas (roughly area north of El Paso, San Antonio, and Beaumont), New Mexico, Arizona, and southern half of California

Cooling Climate South Carolina, Georgia, Florida, Alat>ama, Mississippi, Louisiana, southern 1/3 of Texas, and Hawaii

1.3.2 How is moisture generated?

Indoor moisture generation initially comes from numerous construction conditions and sources.

After construction has been completed, and the initial high concentrations have been removed,

some accumulated construction moisture must still be dealt with in the structure. Source moisture

from the daily activities occurring in the structure and multiple external sources, such as rain

penetration, are the greatest sources of moisture. Moisture is generated by each and every

human, plant, and animal. In addition, many materials, appliances, and processes utilized in our

daily lives and activities generate additional moisture. Some examples and the quantities of

moisture generated from construction, combustion sources, and daily activities are listed in Table

1.2. While these numbers appear to be high in many instances and have not been confimned by

any known research data, the quantities are very similar when compared to the sources from

which the table's data was created. The exact quantities, while seemingly high and questionable

to the author, do make the point that each and every activity that we participate in creates

moisture in our living spaces that must be dealt with in our structure's assembly.

31

Table 1.2, Quantities of moisture generated by daily activities adapted from Rogers (1964) and Straube (2002).

Source Moisture Production Stone concrete 1 ton/1 OOOS.F. of 4" thick floor slab

Gypsum concrete 2.7 tons of water/1 OOOS.F. of 2" roof slab Gypsum piaster 1600 lbs. of water/IOOOS.F. of 1" plaster

Heating salamanders 4.92 liters of water/gallon of oil burned in an unvented space heater People (evaporation per person) 0.75 (sedate), 1.2 (avg.) to 5 (heavy work) liters/day

Humidifier 2-20+ liters/day Hot Tub, Whirlpool 2-20+ liters/day Firewood, per cord 1-3 liters/day

Washing Floors etc. 0.2 liters/day Dishwashing 0.5 liters/day

Cooking for four 0.9 to 2 (3 with gas range) liters/day Frost-free refrigerator 0.5 liters/day

Typical bathingAwashing per person 0.2 to 0.4 liters/day Shower (ea.) 0.5 liters/day

Bath (ea.) 0.1+ liters/day Unvented Gas Appliance 0.15 kg/kWh for Natural gas, 0.1 kg/kWh for Kerosene

Seasonal Desorption (of new materials)

3-8 liters/day depends on the house construction

Plants/ Pets 0.2 - 0.5 (Five plants or one dog) liters/day

While it is impossible to totally eliminate moisture as a source, understanding its movement into

our structures must be better understood by designers and correctly detailed in the design

documents. IVIoisture becomes a concern witliin a structure througli tlie movement mechanisms

of liquid flow, moisture transport due to capillary suction, air movement, and vapor diffusion

(Lstiburek and Carmody, 1991 and Straube, 2002). The principles of moisture movement

regarding each of these topics are critical to understanding the movement of moisture within our

wall assemblies.

1.3.2.1 Liquid Flow Water enters our structures mostly through its flow as a liquid. Water is able to enter the wall

system in liquid form in a relatively short period of time due to the design and detailing of the

exterior envelope. The detailing of splashback is also critical in the design of wall since this is an

area that may allow the base of the wall cavity to pull water back inside and up into the wall cavity

through capillary suction (Fisette, 1995). The detail that deals with splashback may not allow

drained water to fully move away and exit the wall system structure (Fisette, 1995). Wall design,

with respect to liquid flow, can be broken down into three primary methods of construction:

mass/storage walls, perfect barriers, and screened-drainage walls (Straube, 2002; ASTM, 1999).

1.3.2.1.1 Mass/Storage Walls The ideal of the mass/storage wall is a very thick wall section that deals with moisture intrusion

through its mass and thickness of construction. Water only tends to penetrate small distances

through these types of walls and is not as prone to penetrate completely through the wall due to

the girth and width of the wall and the nature of materials typically utilized (concrete, stone, etc.)

32

(Straube, 2002). Water must search for cracks, voids, and openings as it nrraves from the exterior

skin through the entire cross section and then locate openings, cracks, and voids within the

interior sections of the wall for it to migrate from exterior to interior. The path that the water must

travel within this wall section must be continuous since the material thickness and the quantities

being absorbed tend to stop or inhibit water's entry. These walls are very effective at stopping

liquid flow of water, but are nonetheless very expensive, time-consuming, and often difficult to

construct in today's construction market (Straube, 2002).

1.3.2.1.2 Perfect Barriers The perfect barrier type of wall enclosure primarily works well in laboratory and experimental

situations, but can rarely if ever be accomplished for long, if at all, in the built environment due to

poor field construction quality (Straube, 2002). The perfect barrier wall system is the ideal to be

targeted with each construction project. The material must be installed perfectly and then behave

exactly as it was designed. The perfect barrier does exactly what its name implies; it provides

perfect protection from water intrusion. The perfect barrier stipulates that no openings, crack, or

voids exist within the building system. Manufactured homes often strive for this type of

constmction, and builders and designers attempt to create this type of structure by sealing all the

openings and joints during construction (Straube, 2002). This type of construction requires

extreme quality control at all phases of construction installation. Sealants, impervious sidings,

and other means used in perfect barriers break down overtime.

1.3.2.1.3 Screened Drainage Walls The most common type of enclosure in use today is the screened-drainage wall (Straube, 2002).

The screened-drainage wall assumes that water will enter the building system, and then takes

steps to mitigate the harmful effects of water entry into a closed cavity by designing a means of

removal. The design recommendations drawn by this report will utilize the screened-drainage

wall concept since this technique is involved in the residential lightwood frame construction

industry.

Once water has entered the wall cavity it can do a number of different things depending upon the

conditions it is exposed to. Water can become a solid, liquid, or vapor depending upon the

temperature and pressure in its environment. Liquid water may enter the wall cavity through

cracks, voids, openings, and then be absorbed by any material it may come into contact with.

Wood siding and brick are extremely porous materials that allow a great deal of water to pass

through. Once water has penetrated these materials and the exterior skin, the materials on the

interior portions of the wall easily absorb and then diffuse this water. If the water that has entered

the cavity is absorbed and stored by the materials inside the cavity, the water can then be easily

turned from liquid to vapor through processes such as the sun warming the exterior siding on a

33

warm day. Once this liquid has been converted into vapor, it may pass more easily through the

material's pores and any materials that have a higher permeability than the layer where the vapor

currently resides. It may then be moved from its current location to other areas in the wall

assembly as it seeks a state of equilibrium. It is this movement of water in its vapor state that

vapor barriers aim to control. The majority of moisture problems in residential construction are

related to liquid water entry, not vapor condensation generation (Holladay, 2000). The elimination

of liquid water entry into the wall cavities all but eliminates the moisture issue within the building

systems.

1.3.2.2 Capillary Suction Moisture transport due to capillary suction primarily deals with moisture movement into the

building envelope from the exterior and then its redistribution as condensation within the building

envelope (Lstiburek and Carmody, 1991). Capillary suction deals with the moisture pressure

differentials between materials and the transport of moisture across materials where there is no

noticeable break in the material. Typical modes of transport that utilize capillary suction exist

where channels or paths exist in materials that can store or move liquid. It is also common for a

nonabsorbent material, such as metal, to allow water and moisture to be transported when they

are sandwiched together. In the case of a nonabsorbent material used in the wall assembly,

water or moisture can be transported due to pressure differentials that exist within the wall

system. Typically the migration occurs from areas of high pressure to areas of low pressure and

the state of equilibrium is constantly being sought. The vacuum or suction created during this

migration subsequently draws the water upward towards other materials along these similar

material planes.

1.3.2.3 Air Movement Air transported moisture is moved from areas of high air pressure to areas of low pressure and

closely follows the second law of thermodynamics, stated earlier in Section 1.3.1 (Lstiburek,

2000). An air current is the festest means of transferring moisture within a building cavity (DoE,

2002). Air currents move "...in the range of several hundred cubic feet of air per minute" and this

"...accounts for more than 98% of all water vapor movement in building cavities" (DoE, 2002). It

has also been documented that vapor diffusion through a weather resistive barrier would be 2/3

of a pint of water during the heating season while the same material writh a 1/2-inch hole through

it will produce up to 50 pints of water during the same heating season (DoE, 2000). Air leakage is

the most significant mechanism of moisture transfer and should be controlled regardless of

climate writhin a concealed space (Rousseau, 1990; Sherwood and Moody, 1989). The effects of

air leakage must be effectively addressed during the design and then be correctly and carefully

installed during construction.

34

Insulation causes water vapor temperatures to drop rapidly which can cause condensation if the

relative humidity conditions are correct (DoE, 2002). Moisture, when the state changes from

vapor to liquid, is said to have reached its dew point or has reached "the temperature at which a

specific atmosphere is saturated with water vapor", or the temperature at which a volume of air

will become saturated, and below which condensation will occur (ASTM, 1999 and Krogstad and

Weber, 1999). The physics of how moisture contained in air reacts in different temperature

conditions has been defined and documented in psychrometric charts. These charts help

determine where the dew point will be reached within cavities and when moisture within the air

can no longer maintain its gaseous state and becomes liquid condensate (DoE, 2002).

Determining when the dew point will be reached can be accomplished utilizing a psychometric

chart. In order to utilize a psychrometric chart, the designer must make some design parameter

assumptions about the environmental conditions under which the wall assembly will be utilized.

Some of these assumptions include maintaining a constant relative humidity within each material;

no airflow through the assembly, the wall is a perfect barrier, etc. The designer must have the

indoor and outdoor dry bulb temperature and the indoor and outdoor relative humidity conditions.

The design temperatures are not conclusive numbers but are industry accepted approximations

used to calculate the dew point within the wall cavity. The process can be further used to

determine the exact location in the wall assembly that the dew point will be reached. By utilizing

the heat exchange formula obtained from Stein and Reynolds (1992) Mechanical and Electrical

Equipment for Buildinas: 8th Edition, in conjunction with psychrometric charts it is possible to

determine where the dew point will be reached in the assembly. The point where the dew point

occurs is where the designer should place design emphasis and address the effects of moisture.

The following heat exchange formula helps determine these locations:

q = 2:(U • A) At

where, q is the total heat exchange conducted through the building assembly

U and A are specific to each skin element in the building assembly, and

At is the change in temperature difference across the entire building assembly.

The following example shows how the air temperature changes as it move through the building

assembly. The wall section used in the Stein and Reynolds (1992) Mechanical and Electrical

Equipment for Buildings: 8th Edition example is constructed, moving from the interior to the

exterior, of a brick wall, nomnal 6-inch batt insulation, 1/2-inch plywood, and a 1-inch wood siding

(Stein and Reynolds, 1992). Other assumptions that have been made are that the interior air

temperature is 68°F and the exterior air temperature is 32°F (see wall section sketch in Figure

1.1), the relative humidity has not changed through the wall cavity, and the wall cavity is a perfect

barrier (Stein and Reynolds, 1992). The computed temperatures at each material change have

35

been diagrammed in Figure 1.1. The temperatures were computed using the formula discussed

above and the computational calculations have been shown in Table 1.3.

Table 1.3, Calculated temperature change from one material to another within a wall section copied from Stein and Revnolds (1992). Mechanical and Electrical Eauioment

for Buildinqs: 8th Edition R-

value Component SR-value

from interior

Temp Drop from Interior (°F) using (R total at componentffiR for wall asseml)ly) x At

Temp Drop From Outer Edge of

Component (°F)

0.68 Inside air layer 0.68 (0.68/21.46) X 36 = 1.1 68-1.1 =66.9 0.20 Common brick 0.88 (0.88/21.46) X 36 = 1.5 68-1.5 = 66.5 19.00 Nominal 6-inch insulation 19.88 (19.88/21.46) X 36 = 33.3 68-33.3 = 34.7 0.62 1/2-inch plywood 20.5 (20.5/21.46) X 36 = 34.3 68-34.3 = 33.7 0.79 1-inch wood siding 21.29 (21.29/21.46) X 36 = 35.7 68-35.7 = 32.3 0.17 Outside air layer 21.46 (21.46/21.46) X 36 = 36 68-36=32

Then using a psychrometric chart and an accurate relative humidity for the project's specific

location, the dew point can be determined for the wall assembly by calculating the dew point at

each of the various material changes within the wall section utilizing the R-values for each of the

materials, an accurate relative humidity level for the area, and accurate design temperature to be

experienced. A diagrammatic psychrometric chart with sample numbers is shown in Figure 1.2,

and the associated definitions may be referenced from Section 1.2, pages 21 - 22. The dew point

location, under the specific relative humidity and temperature conditions, for the specific designed

J?.**r i, Figure 1.1, Sample wall section with temperature changes diagrammed adapted from

Stein and Reynolds (1992), Mechanical and Electrical Equipment for Buildinqs: 8th Edition

wall assembly will then allow the designer to more easily determine the steps necessary to

address vapor condensation within the particular assembly. The dew point for a specific wall

section should be calculated using the average historical monthly temperatures and relative

36

humidity conditions over tlie course of a year. Once the designer has the dew point locations for

the specific wall section, the specific design details may then be designed to respond to moisture

within the wall cavity.

The following example explains how to utilize the psychrometric chart in determining where the

dew point will be reached under certain design conditions. The sample wall section and

calculated temperatures are used from Figure 1.1 and Table 1.3 and the dry bulb temperatures

are used for the indoor surface and the intersection of the brick and the insulation, the various

dew point temperatures are calculated for the designed wall system by using a psychrometric

chart. The dry bulb temperature is 66.5°F at the material change from brick to insulation. This is

lin s«F£4KBmr Me 6TVP5 toKTtSKT

K»t4gtevpg-"g%rK

Figure 1.2, Sample psychrometric chart, adapted from Stein and Reynolds (1992), Mechanical and Electrical Equipment for Buildings: 8th Edition

from the calculations in Table 1.3 and this point is shown as Point 1 in Figure 1.2 (psychrometric

chart). Following the psychrometric chart lines vertically to the intersection point of the design

relative humidity line (assumed in this example to be 50% relative humidity), and then following

the line of constant enthalpy over to the 100% relative humidity (saturation line) shows that the

dew point for 66.5°F and 50% relative humidity conditions and at this location is 47°F. Following

the same assumptions for the indoor dry bulb 2 (inside air layer temperature) temperature of 68°F

with 50% relative humidity provides the designer with a 49°F dew point temperature. The same

calculations/extrapolations must to be done for all the other surfaces to determine at what

temperature condensation will occur within the wall cavity for each of the various materials. It

37

should be remembered that the relative humidity levels will not remain constant for any climate,

but the designer must use the most representative historical numbers in determining how to

design the wall cavity section and where (if at all) to utilize a vapor barrier in the design.

1.3.2.4 Vapor Diffusion Through the process of diffusion, water vapor is transported from areas of higher vapor

concentration to areas of lower vapor concentrations and is constantly seeking and desiring a

state of equilibrium (Straube, 2002). In order for moisture to be a problem in a constructed

structure, four basic conditions must be satisfied:

1. "A moisture source must be available,

2. There must be a route or means for this moisture to travel,

3. There must be some driving force to cause moisture movement, and

4. The material(s) involved must be susceptible to moisture damage' (Straube,

2002).

Water vapor can also be described by its drive through a material as being either positive or

negative. Positive vapor drive can be described as moisture vapor traveling from moist, warm

outside air to the cool, drier interior area (Kubal, 2000). Typically, much of the country

experiences positive vapor drive during summer conditions, or simply as vapor's desired

movement from the exterior to the interior. Negative vapor drive process describes vapor

movement from the warm, moist interior air being pulled outward to the drier, cooler air by the

differences in vapor pressure (Kubal, 2000).

Vapor diffusion primarily deals with moisture movement from the exterior and from within

conditioned spaces into the building envelope. Diffusion principles are closely related and

associated with air movement and controlling/stopping airflow through the building envelope. The

"diffusion of moisture through a material is a function of its permeance to vapor and the vapor

pressure difference across its surface" and thus by lowering the vapor permeance of the material

the diffusion through it will ultimately be lower (Rousseau, 1990). The overall process of water

vapor diffusion through a wall system is a very slow process. The movement of moisture in its

vapor state is a function of the vapor permeability of a material and the vapor pressure differential

that acts across the wall system's material cross section (Lstiburek and Carmody, 1991). Vapor

diffusion is a function of the specific climatic area where the structure is located. In cold climates,

vapor diffusion will typically move moisture from within the conditioned space into the wall

assembly (Lstiburek and Carmody, 1991). In warm, climates, the vapor diffusion process moves

moisture from the exterior into the building assembly and then into the conditioned space

(Lstiburek and Carmody, 1991). It should be remembered that air leakage and air movement

38

accounts for far more concentrations of moisture movement than does vapor diffusion (Letter,

2000).

1.3.3 How do you deal with the moisture transport mechanisms? Once the moisture transport methods are understood, the designer must then address each

transport mechanism individually and find a solution for controlling moisture's movement within

the structure. In theory, if one of the moisture movement mechanisnns, previously discussed could

be removed from the scenario then moisture as a concern in the structure could be eliminated

entirely (Straube - moisture, 2002). Moisture is all around us, and to fully eliminate any of these

items/sources is impossible. However, employing better techniques and paying more attention to

the detailing of several critical areas during design and in the subsequent construction of the

structures can minimize the harmful effects of moisture within our structures. Placing emphasis

on the effects that moisture has on our structures could eliminate many health concerns and

eliminate building deterioration due to rot in our residences (Trechsel, Achenbach, and Launey,

1982). A key principle to detailing writh moisture in mind is to follow the guidance of "keep it out,

and let it out when it gets in" (Lstiburek, 2000). In order to design a solution, the designer must

address the principles of capillary suction, liquid flow, evaporation, ventilation, and finally vapor

diffusion and air leakage (Straube, 2002). Understanding these principles and concepts is critical

in dealing with moisture within a stmcture and designing a moisture responsive stmcture.

1.3.3.1 Capillary Suction The pull of moisture and water into the building is called capillary suction. One way of breaking

the capillary suction is the incorporation of an air space within the wall that facilitates drainage

and acts as a capillary or surface tension break between the cladding and rest of wall (Straube,

2002). Capillary suction may be created by using similar material surfaces, for example, placing

two plates of glass next to one another creates a plane in which water is easily transported often

draws up water. The same principle exists between the siding and the wall structure and can be

corrected in practical applications by several methods such as: 1.) Painting the siding, 2.) Placing

sealant at laps in the siding, 3.) Placing tacks at laps in siding, 4.) Painting the back of siding or

back-priming the siding, 5.) Designing an air space between the exterior siding and the

nonabsorptive building paper, 6.) Placing siding directly on absorptive building paper, 7.) Leaving

an air space behind brick veneer, 8.) Breaking contact with the foundation soil under the slab, 9.)

Utilizing an air space between the siding and the nonabsorptive building paper, and many others

(Lstiburek and Garmody, 1991). One effective means of breaking capillarity between a footer and

the foundation wall is by placing a sheet polyethylene layer or by applying damproofing on the top

surface of the footer prior to placement of the foundation wall as diagrammed in the Figure 1.3

sketch (Lstiburek and Garmody, 1991).

39

MGMBBANB

1.3.3.2 Liquid flow Drainage and liquid flow of

water that enters the wall

cavity is primarily an issue

of utilizing good detail

design and then

implementing effective

quality control during the

construction. Resistance

of the wall to water

intrusion is determined by:

• Resistance of the

wall to leakage

(Carll, 2000),

• Resistance of the

materials within the wall to be damaged should they become wet (Carll, 2000), and

• Ability of the wall to rapidly dissipate any intruding water entering the cavity (Carll, 2000)

FftoifMG-'

Figure 1.3, Sample footer diagram adapted from Lstiburek and Carmody (1991), Moisture Control Handbook:

New, low rise residential construction

Leakage can best be dealt with through ventilation applications and allowing any liquid flow of

water that may enter the wall cavity to escape through weeps or other intentionally designed

drainage points. Liquid flow escaping through weeps and drainage points acknowledge that

water will enter the wall cavity and as such must be allowed to escape. To properly handle this

liquid entry, proper flashing techniques are the first layer of defense for the structure. Flashing,

drip edges, and appropriate sloping must all be con-ectly designed and then constmcted (Straube,

2002). Excellent checklists were developed in Paul Fisette's article, "Making Walls Watertight",

which addressed the critical areas of a wall and things to be accomplished during construction.

The checklists have been recreated and consolidated in Table 1.4 for reference when perfonning

quality control on a residential construction project's housewrap, corner boards, vwndow flashing,

and siding (Fisette, 1995).

Table 1.4 - "Making Walls Watertight" Checklists From Paul Fisette's article, "Making V\falls Watertighf from Journal of Light Construction, Volume 14, Number 3, December 1995, pages 35-38.

Housewrap Checklist "Use housewrap or felt paper on all houses, no matter what kind of siding you are using." "The wrap should be continuous; avoid patchwork of small pieces." "Provide an unrestricted path down and out of the space behind the siding. Wall membranes should overlap by 3 inches horizontally and 6 inches vertically. Tape all seams." "Protect all pathways into the building envelope by lapping housewrap over flashings."

Corner Board Checklist "Install felt paper or housewrap at all corners." "Double-wrap corners by applying vertical felt or housewrap splines under the corner boards." "Don't caulk the joint between the siding and corner board; caulk deteriorates over time, providing a

40

pathway for water to get into the frame and preventing trapped water from escaping." Window Flashing Checklist

• "Protect the top of the window flashing with overiapping wrap." • "Double-overlap housewffap around nailing fins of vinyl and dad windows." • "At sills, splines must direct water over underlying housewrap." • "At head, leave a 1/4 inch gap between the window flashing and bottom edge of siding to prevent wncking of moisture." Siding Checklist

• "Don't install board siding on a diagonal." • "For horizontal board siding, use tofvgrade boards with no knots, splits, or other defects. Install

T&G and shiplap siding so that the joints between boards drain away from the sheathing." • "For panel siding, use housewrap over studs. Housewrap should overlap Z-flashing at the joint

between panel courses." • "Protect wall sheathing dose to grade with bituminous membrane." • "Siding should overlap sill-to-foundation joint by at least 2 inches."

Proper drainage is also done through the implementation of weep holes or designing drainage

points corrertly. Weep holes, when they are utilized, should be kept free of obstruction and the

path leading to the weep holes should be clear so that water can travel to and exit through these

designated points easily and readily (Lstiburek and Carmody, 1991). The importance of the weep

holes and drainage points also facilitates the implementation of ventilation within the structure's

wall cavity (Lstiburek and Carmody, 1991). The approaches to weep holes and drainage points

should be properly sloped, and elevated correctly so that water cannot flow into the openings

from the outside but still exit the wall easily. The area around these openings should also be free

of any outside obstructions such as vegetation and soil embankments that could hamper air

circulation or drainage. The openings should be clear and visible from the exterior of the

structure. Regardless of the wall assembly design, proper drainage must be considered and

designed to allow for drainage at the bottom of the wall.

In order to properly deal vwth leakage and drainage in construction several principles should be

remembered:

1. Think like water!

2. "If you can't figure out how to flash it, don't build it." (McDaniel, 2000)

3. Water is easily controlled if you design a path for it to flow, remember typically water

flows downhill except under capHllary suction conditions.

4. "Water is lazy. Water will always choose the easiest path to travel." (Lstiburek,

2000)

5. Pay attention to how you flash, lap and layer any flashing or housewrap in the flow

direction. (McDaniel, 2000)

6. A weather resistive barrier is nothing more than a drainage plane to control the flow

of water. (DoE, 2000)

7. Avoid capillary suction by designing effective breaks at suspected junctions that

promote this condition.

41

1.3.3.3 Evaporation The evaporative process of moisture within the wall cavity is very closely related to the properties

associated with ventilating the wall that will be discussed in the next section. However,

evaporation may occur from the inside or from the outside (Straube, 2002). Evaporation is tied to

the characteristics of the specific, individual material utilized (Straube, 2002). The evaporation

process is difficult to separate and closely related to the ventilation properties contained in the

designed wall cavity.

1.3.3.4 Ventilation Ventilation of the wall assembly is a good means of dealing with moisture and leakage and

provides a means of drying components should they get wet. Ventilation follows the air pressure

differential principle that was discussed earlier and allows rising air heated by the sun to pull air

and force air movement within the wall cavity (Straube, 2002). The air pressure differential

principle allows for the difference in pressure across the wall section to act as a means of pulling

air into the wall cavity while facilitating pressure equalization through the process of convection.

Designing an exit, as well as an entry, allows airflow to move through the wall creating convection

patterns within the cavity, and cavity condensation may be controlled by facilitating control over

where condensation could accumulate (Straube, 2002).

Ventilation should be closely examined and investigated in relation to the climatic area that the

structure is being designed for. Ventilating may be detrimental and actually facilitate adverse

moisture conditions within the wall cavity in certain climatic areas. As a general rule, the wall

cavity design should not be ventilated in a hot, humid climate due to the fact that warm air is

capable of maintaining and holding more moisture than cold air. Ventilating in this area could add

to the moisture levels within the wall if air were allowed to freely flow through the wall in these

areas (Lstiburek and Carmody, 1991). For the other more temperate and cold regions of the

country ventilation of the wall cavity should be encouraged. Minimizing holes and penetrations to

lower the air volume change within the wall cavity could inadvertently facilitate wetting of the wall

cavity materials and reduce the opportunity for drying to occur (Lstiburek, 2000). By not allowing

moisture that accumulates within the wall cavity to dry, interior moisture levels rise and

condensation could become visible on interior surfaces and windows. The conditions favor

mold/mildew growth, and ultimately decay within the wall cavity and attic spaces if the problem

goes unnoticed for long (Lstiburek, 2000). The need to dehumidify the space or implement

dilution ventilation is necessary to help eliminate these types of problems in the unventilated wall

cavity (Lstiburek, 2000). An air space utilized in design should have "a clear space with a

minimum thickness of 3/8 of an inch, although 1-2 inches is recommended" (Lstiburek and

Carmody, 1991).

42

1.3.3.5 Vapor diffusion and air leakage Vapor transport through diffusion and air leal<age can best be understood once the difference

between an air banier and a vapor barrier has been explained. In wall assemblies there are two

primary barriers that are installed, but they perform drastically different roles in dealing with

moisture and vapor penetration within the wall assembly. These two barriers, vapor and air, are

typically used or required by code during the construction of a structure. The purpose and use of

air and vapor barriers are often confused by the designers, builders, and code officials (Straube,

2001). it should also be remembered that water vapor moves through the processes of vapor

diffusion, air transport mechanisms, heat exchange, and the other means previously discussed

that deal with water's movement (Lstiburek, 2000). To help simplify and clarify the differences

between these two barrier/retarder systems, definitions and sample material lists are provided in

Table 1.5 below.

Table 1.5 -Vapor Barriers vs. Air Barriers. Definitions and Sample Materials

Definition Sample Materials VDR/Vapor barrier

'the control of water vapor diffusion to reduce the occurrence or intensity of condensation" (Straulje, 2001) that is driven by diffusion, and may have imperfections and small cracks in its surface without greatly impairing the performance of the permeal)le vapor barrier (Straube, 2001), or defined by building codes as anything with a permeability of 1 penn or less (Lstiburek, 2000)

- Polyethylene sheet membrane (Visquene) or film (varying thicknesses, 2-6 mil and in 3-20 foot rolls) sealed vrith manufacturer recommended caulk, sealants, and tapes -EPDIWI - Piastre sheeting - Rubber membranes -Glass - Aluminum foil - Sheet metal - Oil-based paint - Bitumen or wax impregnated kraft paper - Wall coverings and adhesives - Foil-feced insulating and non-insulating sheathings - Vapor retarder latex paint - 2 coats of acrylrc latex paint top coating with premium latex primer - 3 coats of latex paint - Scrim (open-weave fabric like fiberglass ^bric) - Hot, asphaltk; rubtierized membranes - Some insulations (elaslomeric foam, cellular glass, foil foced isofbam) if sealed - Aluminum or paper feced fiberglass roll insulation - Foil backed wall board - Rigid insulatbn or faam-board insulation -1/4 inch Douglas fir plywood with exterior glue - High-perfomiance cross-laminated polyethylene

(Information fi-om Lstiburek, 2000; ICAA, 2002; Spence, 1998; Bordenaro, 1991; Maness, 1991; Lotz, 1998; Lstiburek and Cannody, 1991; Forest Products Lab, 1949; DoE, 2002)

Air Barrier/ Pressure Threshold

"control airflow and thereby control convection vapor transport" (Straube, 2001), controls the moisture that is transported along with this airflow (Straube - vapor, 2002); helps to increase comfort, reduce energy consumption, help control odor, and help reduce sound transmission (Straube, 2001); and must be "continuous, durable, stiff (or restrained), strong, and air impermeable

- Unpainted gypsum board (sealed) - House-wffap, if properiy sealed and continuous - Continuous building paper (15# or 30# felt paper) -Plywood - Foam board insulatfon - Hot, asphaltb rubberized membranes - Some insulations (elastomeric foam, cellular glass, foil laced isofbam) if sealed

43

Definition Sample Materials (Straube,2001) (Infonnation from ICAA. 2002; DoE, 2002)

Now that these two barriers have been defined and some sample materials that qualify as air and

vapor barriers have been listed, we can begin our discussion of why we would utilize these

materials in a wall assembly.

The function of an air barrier is to stop outside air from infiltrating into the building through the

walls, windows, or roof and to keep inside air from exfiltrating through the building envelope to the

outside (Quiroutte, 1991). An air barrier may be utilized at any location within the wall assembly,

but the designer must always consider the following points when designing an air barrier

• Air barrier must be continuous throughout the building envelope. The wall must be

continuous with the roof and must be connected to openings such as doors,

windows, etc. (Quiroutte, 1991),

• Must be securely fastened to the structure to resist vwnd load, stack effect, and

pressurization from mechanical systems (Quiroutte, 1991),

• It must be virtually "air-impemieable" (Quiroutte, 1991),

• Avoid air leakage, cracks, and holes in construction (Handegord, 1982),

• Air tightness must be designed, constructed, and maintained around all details

(Handegord, 1982),

• Permeability of the material used as an air barrier must be determined (Rousseau,

1990),

• Ease of detailing and building a continuous assembly with the contract documents

(i.e., Can it be built as designed?) (Rousseau, 1990),

• Sequencing of wall assembly during construction (Rousseau, 1990),

• Ease of inspection and performing maintenance once installed (Rousseau, 1990),

and

• Material durability at the selected location (Rousseau, 1990).

An air bamer must be specifically designed, detailed, constructed and in order to ensure that it is

effective (Rousseau, 1990). Since air leakage is the most significant mechanism to be

considered in moisture control, it should be controlled regardless of climate. It should be

remembered that air leakage moves far more moisture than vapor diffusion does through

materials (Sherwood and Moody, 1989 and Letter, 2000). A key principle to be remembered with

an air barrier is that they should be used everywhere, and they should he properly designed and

subsequently constructed (Straube, 2002). A fine line exists because the reduction of air

infiltration in homes today has helped create the moisture dilemma since wall systems hold more

moisture than they used to because of better insulation and airtight construction techniques (U.S.

Forest Service, 1949). The honnes of decades past were able to breathe more Oe., "the old drafty

44

house") and were better able to transpire and reduce the accumulated moisture being generated

by our daily activities (Wettemrian, 1982). It has been reported that a family of four produces 7.5-

12 liters of moisture per day and that the comfort level for humidity in a house is only 2.5-3.5 liters

of air-borne moisture within a 2000 ft^ house (Wetterman, 1982). The excess moisture must be

dealt with in our homes.

Air that leaks into a wall assembly must also have means to exit the assembly and, in most

cases, can be corrected through careful detailing and maintaining quality control at the inlet

openings and outlet openings are the sources of air leakage into wall assemblies (Lstiburek and

Carmody, 1991). Inlet openings are typically unsealed electrical outlet boxes, bottom edges of

interior gypsum board cladding, or openings/gaps/joints in interior air barrier systems. Outlet

openings are joints between sheets of exterior sheathings, top plate and bottom plate

connections to the exterior sheathings, service penetrations, and other construction flaws. These

openings must be detailed and constructed correctly if the air barrier's integrity is to be

maintained.

Major points to be considered with regards to air barriers are:

• Air barriers often act like vapor barriers due to the permeance of the materials used

(Straube, 2002).

• The designer should consider whether or not the air barrier material qualifies as a vapor

barrier because utilizing a redundant system will lead to harmful moisture issues within

the wall cavity by trapping vapor inside layers creating an ideal environment for rot,

decay, mold, and fungi to flourish in (Roger, 1964). Examples of easily incorporated

inadvertent vapor barriers include vinyl wall coverings and multiple coats of paint (i.e., 3

coats of latex paint) that inhibit the wall's capacity to dry.

• In order for an air barrier to be totally effective, an airtight seal must be maintained

between all elements that the air barrier comes into contact with (James, 2000).

• A vapor barrier may have holes, but the air barrier must be continuous and free of holes

in order to control any unwanted water vapor movement (Lstiburek, 2000; DoE, 2002;

Lstiburek and Carmody, 1991).

• The specific location of the air barrier within the wall cavity is not as important as the air

barrier maintaining "intimate contact" with the insulation so that the cavity does not

promote conditions that facilitate convection and the subsequent moisture generation

problems associated with these air currents (Quiroutte, 1991).

Air leakage through a wall assembly nearly approaches zero in modern construction because of

the rampant use of sealers and caulks between any and all the joints and materials (Straube,

45

2002). While the approach spedfied by most designers calls for the use of housewrap as the air

barrier, they should be cautioned since this material has been shown in the DOE (2000), Holladay

and Vara (2000), McDaniel (2000), Holladay (2000), Cushman (1997), and James (2000) articles

to allow air to pass through once it has been stapled or attached by other means. While all the

joints may be taped, as directed by the housewrap manufacturer, tapes, and sealants are prone

to deterioration over time. A full discussion of housewrap cannot be adequately discussed for the

brevity of this report (references for an initial investigation of housewraps has been included in

the bibliography). The importance has been mentioned since housewrap is a critical component

that must be considered and designed when dealing with moisture. Two principles should be

remembered: 1.) "If all building assembly openings are controlled then air movement as well will

be controlled" and 2.) A tight assembly equals less air movement, which equals less moisture

movement (Lstiburek and Carmody, 1991). Once air movement is controlled, how the designer

deals with and details for the potential moisture accumulation becomes the central concern in wall

cavity design.

While the five subjects of 1.) evaporation, 2.) capillary suction, 3.) leakage, 4.) ventilation, and 5.)

diffusion all seemingly act independent of one another, the areas must be designed, detailed, and

constmcSed with an understanding of how each separate component's behavior affects the other.

Failure to address each subject correctly could potentially lead to moisture related concerns

within the cavity wall system. It has been reported "with the exception of structural errors, 90% of

building construction problems (are) associated with water" (Trechsel, Achenbach, and Launey,

1982). We shall now investigate why vapor barriers, termed vapor diffusion retarders by

ASHRAE (and to be referred to as vapor barriers from here forward), are used today and then we

will look at how the literature reviewed says they should be used.

1.3.4 Why vapor barriers are used today? A vapor banier's performance is measured in perms, which is "the passage of one grain of water

vapor per hour through one cubic foot of material at a pressure differential of one inch of mercury

between the two sides of the material" (Allen, 1990). A vapor barrier is any material that has a

permeance of less than or equal to 1 in residential constmction, but this number is typically much

lower for other types of construction (ASTM, 1999; Lstiburek, 2000). Materials that are

intentionally utilized as a vapor barrier have a perm rating of .1 or less, even though the definition

provides for less stringent permeance characteristics (DoE, 2002). To further prevent any

trapping of moisture in the wall cavity, the cold side of the material should have a perm rating at

least five times greater than the value at the warm side (DoE, 2002). The penneance of the vapor

barrier becomes purely academic once a hole is made, therefore, any work occurring after the

installation of the vapor barrier should be checked to ensure that no major tears, punctures, or

46

damage has disturbed its surface integrity (Lotz, 1998; Wilson, 1999). A vapor barrier should be

included in the wall system design when the designer is seeking to create a moisture and

infiltration tight environment for the wall system (Stein and Reynolds, 1992; Lstiburek, 2000). A

vapor barrier is not a waterproofing application; it is a material with a low permeance that aims to

slow or retard the movement of vapor through the material to prevent the vapor from reaching the

dew point on another surface (Bordenaro, 1991; DoE, 2002; Kubal, 2000; ASTM, 1999; Quiroutte,

1991; DoE, 2002; Straube, 2002; Lstiburek and Carmody, 1991; ICAA, 2002).

The incorporation of a vapor barrier in the wall system can be looked at as a means of controlling

condensation in wall assemblies. The vapor barrier is expected to control condensation,

regardless of how the moisture entered the cold side of the assembly (Rousseau, 1990; Forest

Products Lab, 1949). Stewart Rogers (1964) summarized prevention of condensation in buildings

as "keeping the indoor air dry or keeping impervious interior surfaces warm or keeping moist air

from coming into contact with cool surfaces." He enumerated six steps for accomplishing this

task (Rogers, 1964).

1. "Get rid of excess moisture" through drainage, venting, and isolating moisture generating

sources" (Rogers, 1964).

2. "Keep moist air away from cold surfaces" by using a vapor barrier or other vapor

impervious materials (Rogers, 1964).

3. "Keep critical surfaces warmer than dew point temperature" by insulating the cold side

and not using thermally effective material on the warm side of the vapor resistant

components (Rogers, 1964).

4. "Allow water vapor within construction to escape through the cold side" by designing the

outer skin with a vapor porous material or by using air vapor paths through vents in the

skin (Rogers, 1964).

5. "Avoid vapor traps' by not using a double vapor barrier or unintended vapor barrier and

using vented flashing in built-up roofs (Rogers, 1964).

6. "Use absorbent materials that can hold transient condensation harmlessly" by allowing air

circulation over indoor surfaces to prevent and encourage reevaporation of any moisture

the materials may acquire (Rogers, 1964).

The principles of vapor drive mentioned eariier, Section 1.3.3, pages 32-39, are a prime reason

for incorporating a vapor barrier in the wall system design. In winter, the warm, moist interior air

is drawn outward to the drier, cooler air by the differences in vapor pressure associated with

negative vapor drive (Kubal, 2000). The opposite tends to occur in the summer when the

moisture vapor travels from the moist and warm outside air to the cool, dry interior area called

positive vapor drive (Kubal, 2000). Vapor drive within the cavity is the process through which

47

materials seek a state of equilibrium and move vapor to other parts of the wall system. A vapor

barrier is useful in the battle against vapor drive and the moisture contained in the migrating air

(Kubal, 2000).

If the building design provides for an air barrier and is constructed correctly wîth no openings, the

airflow and its capacity to move water vapor into and through a wall system can be elinranated.

Vapor diffusion must then be designed for and implemented in the structure because heat

transfer, air transport, and vapor diffusion are the only means through which water vapor can

move within a wall system (Lstiburek, 2000). The continuity of the vapor barrier is not as

important as the continuity of the air barrier. However, the vapor bamer shouW be as impervious

as possible, and continuity should be striven for since air movement should be minimized when

aiming to control vapor movement (Lstiburek, 2000; Lotz, 1998; DoE, 2002). The effectiveness

of the vapor banier is said to be proportional to its continuity and integrity Q.e., a vapor barrier that

has 10% of its surface area vflth openings is 90% effective against vapor diffusion) (Lstiburek,

2000). If the vapor barrier also fulfills the role of the air barrier, then the vapor barrier must be

installed in the same manner as the air barrier in order to be effective in both roles.

If the wall system is detailed correctly, the flashing should be carried up and through the vapor

barrier so that any condensation that does build up on the vapor barrier will have a designed path

for the liquid condensate to exit the wall system (DoE, 2002). Vapor barriers stop the drying

process, so there must exist a means of allowing water to be removed from the wall system

(Straube, 2002). Storage capacity should be determined for each specific material that is to be

used as a vapor banier (Shenwood and Moody, 1989).

1.3.5 How do you use a vapor barrier? In a cold climate, a vapor barrier should be installed as close to the warm side of the wall or

thermal insulation as possible to aid in preventing water vapor from entering the insulation and

condensing into liquid at the point where the air temperature inside the cavity drops and reaches

the dew point (Stein and Reynolds, 1992; Allen, 1990; Kubal, 2000; Rogers, 1964; McGinley and

van der Hoeven, 1999; Quirouette, 1991; Lotz, 1998; Sherwood and Moody, 1989). The

application of a vapor barrier on the warm in winter side of the insulation tends to reduce the

temperature and relative humidity of the structure (Rogers, 1964). Any material used on the cold

side of the vapor barrier should see a rise in the permissible relative humidity and temperature of

the wall section (Rogers, 1964). Typically a vapor barrier is a plastic film and is placed just

behind the interior wall surfaces (gypsum board and flooring) (Stein and Reynolds, 1992).

However, in hot, tropical areas the vapor barrier should be placed on the exterior side of the

insulation to prevent condensation from wetting the insulation as the air migrates under positive

48

vapor drive (Kubal, 2000; Lotz, 1998). In mild, more temperate climates, a vapor barrier may or

may not be necessary. The specific wall assembly design and climatic conditions should be

calculated when deciding whether or not to use a vapor bamer regardless of the climate.

A vapor barrier may be accidentally or inadvertently installed in the wall system due to the many

types of materials that qualify as a vapor barrier as seen in Table 5 in Section 1.3.3.5. All

material permeance ratings should be checked prior to being installed in the wall system

(Rousseau, 1990). Many materials that are used behave like a vapor barrier and often trap

moisture within the wall system, which often leads to deterioration, moW and mildew growth,

and/or corrosion if left uncorrected or unnoticed (Maness, 1991). The vapor barrier should be

installed in a seamless, or as near to seamless, as possible manner to reduce air infiltration

(Allen, 1990). The vapor barrier sheet application should be lapped and sealed to prevent any

breaks in the barrier, and any holes or cracks should be sealed if the vapor barrier is to perform

adequately in retarding moisture (Kubal, 2000; Maness, 1991). A vapor barrier is often attached

as a finish to batt insulation material (for example, wax impregnated kraft paper), or the vapor

barrier may be applied separately, which is often preferred by designers because of the fewer

number of seams that have to be sealed during construction (Allen, 1992).

A vapor barrier should not be used in a waterproofing application role because of its low

permeability. The vapor barrier does, however, act quite effectively at preventing and breaking

the upward capillary movement of vapor into the pores of concrete by providing a contact break

with the soil located sub-slab (Kubal, 2000; Lstiburek, 2000). According to Lstiburek and

Carmody (1991), moisture is also prone to collect as condensation at the following interchanges

where vapor barriers are often used:

Insulation and sheathing

Sheathing and building paper

Building paper and cladding.

An air mass that is cooled below its dew point can no longer retain the vapor that is being earned

and condensate may be formed (Allen, 1990). The specifics of where to locate the vapor barrier

should be calculated for the specific climatic condition and the specific wall system as discussed

and calculated earlier in Section 1.3.2.3. The particular orientation of the structure also plays a

critical role in locating where, if, and when to utilize a vapor banier. Each of the north, south, east

and west facing walls have different design parameters due to the varying climatic conditions

each orientation presents. The purpose for locating the vapor barrier near the interior surface, in

most heating climates, is because the higher indoor air temperatures are capable of carrying

more water vapor that can reach the dew point when the air current reaches the insulation (and

49

cools down) as the air passes through the wall cavity (Allen, 1990). In hot, hurrwd warm weather

climates, the vapor barrier should be located outside of the insulation and in other mild climates a

vapor barrier may not even be needed (Allen, 1990).

The incorporation of a vapor barrier in a mixed climate is the area that remains most vague and

for the most part neglected in the literature reviewed. The primary difference for determining

whether to use a vapor barrier or not depends upon understanding the nature of vapor movement

and the potential for drying within the specific wall system design. The ASTM recommends

utilizing a flow-through design approach, and this approach closely follows other research and is

logical for combating the moisture problem. The flow-through design approach acknowledges the

fact that wetting will occur from one side of the wall system during one season, and that the wall

system will allow drying in the next season from the opposite side. Following the flow-through

approach for the mixed climate region of the country is the most logical approach from a design

perspective. The design for these types of wall systems must be closely examined and

investigated because the potential for creating a redundant or inadvertent vapor barrier system

within the wall cavity creates the ideal environment for problems associated with vapor

accumulation, such as mold, nruldew, and ultimately decay.

The following is in specific reference to the roof, however, the principle also applies to the wall

assembly as a whole. "The specific location of the vapor barrier in the wall system should be

determined by calculating where the dew point is located in the system and then placing the

vapor barrier at a location above the dew point, if the dew point is outside of flie system, a vapor

barrier may not even be needed" (Bordenaro, 1991). The geographic conditions (specific number

of cooling and heating days) and orientation of the designed walls should be investigated and

specifically designed for when considering the inclusion of a vapor barrier in the wall system

(Allen, 1990). A vapor banier should be located on the outside face of the insulation in hot,

humid climates and on the inside face of the insulation in cold climates (Krogstad and Weber,

1999). As a general rule, the colder the climate the greater the need for a vapor barrier within the

wall system (ICAA, 2002).

The codes (CABO: One and Two Familv Dwelling Code. 1995 Edition. Fourth Printing, and

International Residential Code: For One and Two Family Dwellings) call for the cold regions of the

United States to use the vapor barrier on the interior of the building assembly since moisture

tends to migrate from inside to outside (Lstiburek and Carmody, 1991). Wetting of the wall

system tends to occur from the interior, and drying tends to occur towards the exterior in a

heating climate. Therefore, a vapor barrier and air barrier should be installed towards the interior

(Lstiburek, 2000). The purpose of locating the vapor barrier as prescribed by Lstiburek is to

50

prevent the wall system from becoming wet by Interior sources. It Is recomnriended that the

exterior sheathlngs be made of permeable materials (Lstiburek, 2000). A sample wall section for

this heating climate may be referenced in Figure 1.4.

6â« Lflse/tip. eicp^p.^ eypSuM Bxsapo

Figure 1.4, Samiple heating climate wall section adapted from Rogers (1964), Themfial Design of

Buildings

The cooling climate (hot, humid)

regions of the United States

should have a vapor barrier

installed towards the exterior of

the building assembly because

moisture tends to migrate from

the outside to the inside

(Lstiburel< and Carmody, 1991).

The role of the vapor barrier in

this climate is to prevent the

wetting of the wall assembly from

the exterior due to the moist air drive from the exterior towards the cool, interior air (Lstiburek,

2000). Therefore, the vapor barrier and the air barrier system should be installed towards the

exterior of the wall assembly

(Lstiburek, 2000). The purpose

of this design strategy is to

facilitate drying towards the

interior if the wall assembly were

to get wet from moisture's

infiltration. A sample design for a

wall system for this climate can

be seen in Figure 1.5.

IW»CEDftOeMWBUB5

•SWUB> OfP9JH heK^ W'tTH

Figure 1.5, Sample cooling climate wall section adapted from Lstiburek (2000), Builder's Guide to

Mixed Climates: Details for Design and Construction The largest portion of the United

States falls into the mixed

climate region. The mixed climate region experiences one half of the year of inside to outside

moisture movement and the other half outside to inside moisture movement (Lstiburek, 2000 and

2002). In this instance the design would necessitate a "flow-through" design approach, which is

defined by ASTM as "unidirectional vapor flow in installations where any water vapor that diffuses

into the insulation system is permitted to pass through without significant accumulation" (ASTM,

1999). The "flow-through" approach includes utilizing permeable and semi-permeable material

on the interior and exterior surfaces (Lstiburek, 2000). An appropriate material would be kraft

paper faced insulation installed towards the interior so that the kraft paper faced insulation

51

behaves to satisfy the "flow-through" conditions at the respective times of the year (Lstiburel<,

2002). A sample "flow-through" wall may be seen in Figure 1.6. Another appropriate design

approach for this climatic area

would be to implement and utilize

the normal assembly design

implemented in either the cold or

hot, humid climates. Designers

utilizing this approach accept

moisture accumulation in the wall

assembly for part of the year and

assume drying will occur during

the other part of the year

(Lstiburek, 2000). The last

alternate design approach for this climatic region would be to install the vapor barrier

(impermeable/semi-impermeable insulating sheathing on the exterior of the cavity wall system,

like 1.5 inch foil-faced insulating sheathing) in the middle of the wall assembly (Lstiburek, 2000).

A sample of this wall system designed for this climatic region can be seen in Figure 1.7.

Figure 1.6, Sample mixed climate wall section adapted from Lstiburek (2000),

Builder's Guide to Mixed Climates: Details for Design and Construction

Foundation design is an area that is often overlooked and poorly detailed during residential

construction. Concrete is a permeable material and water migrates through concrete over time.

An article written in Concrete

Products in the "Contractor Talk"

column points out that there are

four conditions under which a

vapor barrier should be

implemented. The conditions are

as follows:

"1. When an impermeable

surface will be

applied to the

concrete surface,

such as sealers or

coatings,

2. When goods or merchandise stored on the floors is moisture sensitive,

3. When moisture on the floor will damage machinery, and

4. When installed flooring and adhesives are moisture sensitive." (Anonymous, 1993)

Figure 1.7, Sample mixed climate wall section adapted from Lstiburek (2000),

Builder's Guide to Mixed Climates: Details for Design and Construction

52

The article also stated two conditions under which the implementation of a vapor barrier would

probably not be necessary:

"1. When the building sites are well drained and the water table is normally well below

the ground surface elevation, a compacted layer of granular fill at least 4 in. thick can

be placed in place of a vapor barrier. This has often been proven satisfactory when

the floor coverings and adhesives are not moisture sensitive, and

2. Where no soil moisture problems exist or regions where irrigation, heavy sprinkling

and high rainfall are not common." (Anonymous, 1993).

The implementation of uninsulated crawl spaces has led to an increased stack-effect vapor

movement and in general a rise in overall moisture content within the wall (FPL, 1949; Lstiburek

and Carmody, 1991). Uninsulated, bare earth crawl space often has condensation and moisture

associated problems. Designers often combat this problem in the cold, mixed, and hot, humid

areas using heavy roll roofing underlayment or by applying a membrane vapor barrier in the crawl

space (FPL, 1949; Lstiburek and Carmody, 1991; ICAA, 2002). Implementation of a moisture

cover over the ground in a crawl space will help to minimize the moisture migration into the

structure from the ground below (ICAA, 2002). The correct height of the ventilated crawl space is

one that wouW be sufficient for maintenance to be done. The crawl space should be properly

graded for drainage and have adequate drainpipes to remove any water that may accumulate in

this space away from the wall cavity (U.S. Forest Service, 1949).

The design of vapor bamer underlayment, as recommended by the American Concrete Institute,

shouW include a 3-inch thick layer of sand or gravel over the vapor barrier before placing the

concrete for the slab (Suprenant, 1994). Gravel with sand, to fill in the voids between the gravel

pieces, is the preferred material since gravel would not be moved or displaced as easily during

the placing of the concrete as a straight layer of sand (Suprenant, 1994; Anonymous, 1993). The

recommended vapor barrier for the sub-slab location is a 4-6 millimeter polyethylene membrane

or other membrane (EPDM if high durability is desired) with all joints lapped at least 6-inches

(Suprenant, 1994; Anonymous, 1993; Lstiburek and Carmody, 1991; Rogers, 1964). During the

placement of concrete, the vapor barrier should be protected from any punctures since a hole in

the vapor barrier would allow the concrete to become a channel for the moisture movement that

the vapor barrier was designed to prevent (Suprenant, 1994).

Many lawsuits are filed each year related to moisture problems that have originated at the

juncture of the roof to the wall (Cash, 1993). The poor construction of the roof/wall joint is

primarily due to poor detail design of the flashing and subsequent poor field construction because

the laborers and/or designers do not understand the principles of water movement or are not able

53

to visualize a means of flashing the joint correctly t)ecause of the complexity of the design (Cash,

1993). Moisture and condensation are troublesome at this joint because of the potential for a

redundant vapor barrier. The need for a vapor barrier in the roof or ceiling is not a universal

solution, but should be evaluated just as the implementation of a vapor barrier should be

elsewhere (Cash, 1993). The conditions in the roof/ceiling and the incorporation of a vapor

barrier should be considered in conjunction with whether or not the space is ventilated (ICAA,

2002). A ceiling with a space above and proper ventilation may not require a vapor barrier (ICAA,

2002). The ICAA has reported, "if sufficient attic ventilation exists, condensation problems do not

occur in most U.S. climates' (ICAA, 2002). Climates that should not be ventilated include hot,

humid and cold, hostile, arctic/subarctic climates where moisture/condensation problems are

induced through ventilation and the general inability for drying to occur (Lstiburek and Carmody,

1991). The codes rCABO: One and Two Familv Dwelling Code. 1995 Edition. Fourth Printing and

International Residential Code: For One and Two Family Dwellings) require less ventilation in

attics and crawl spaces if a vapor barrier has been incorporated in the structure (Shenwood and

Moody, 1989).

1.4 Summary Moisture dissipation from within a wall is directly related to both air movement and vapor diffusion

(Caril, 2000). The rampant use of intentional vapor barriers in residential construction is in many

instances creating redundant vapor barriers systems within the wall cavities, thus trapping

moisture and water that cannot escape. Even when the vapor barriers are not redundant, the

placement is often times in the wrong location, which creates as many problems as redundancy.

A vapor barrier's location should be carefully designed in relation to the specific wall design,

climatic conditions, and orientation. In order to control moisture, designers and builders must

look holistically at the indoor and outdoor atmospheric conditions as well as the design of the

building system to create the appropriate foundation, walls, and roof interactions in the wall

assembly (Caril, 2000). Regardless, the recommended placement of a vapor barrier cannot be

universal.

The following points are what seem to be the most important and salient points discovered in the

course of this literature review:

1. Air moves far more moisture through materials than diffusion.

2. In a cold climate, a vapor barrier should be installed as close to the warm side of the wall.

3. In hot, hunrwd, and tropical areas a vapor bamer should be placed on the exterior (warm)

side.

4. In mild, more temperate, climates a vapor barrier may or may not be necessary.

5. A vapor barrier in a basement should be implemented in the same manner as it was in

the above-grade wall system.

54

6. A vapor barrier should be only used if needed, and the use should be determined for the

specific wall system design, climate, and orientation (North, South, East, West) where the

structure will be located.

7. A vapor barrier is a good ground cover below slab-on-grade, and it is important in crawl

spaces. The vapor barrier should help reduce moisture transport through capillary

movement fi'om the soil into the stmcture.

8. The vapor barrier does not have to be impervious, but should be installed with as few

imperfections as possible to prevent the flow of air.

9. Multiple layers of paint (the non-vapor retarding type, i.e., latex), 3+ coats, behave like a

vapor barrier.

10. Wallpaper, especially vinyl wall covering, behaves like a vapor barrier.

11. The wall cavity should not be ventilated in hot, humid (cooling) climates.

12. The wall cavity shouki be ventilated in temperate and cold (heating) climates.


14. Care should be taken when installing an air barrier because the air barrier is only as

functional as the air barrier's material integrity (i.e., be impervious to cuts, tears,

punctures, rips, etc.).

15. House wrap is a greatly misunderstood material despite its prolific use in residential

construction.



17. All walls are different and will behave differently depending upon where and how they are

to be constructed.

55

1.5 References Cited

Allen, E. (1990). Fundamentals of Building Construction: Materials and Methods. 2nd Edition. John Wiley and Sons, Inc.; New Yorl<; 803 p.

American Society ofTesting and Materials (ASTM). (1999). ASTM Standards in Building Codes. Volume 2: Designation C 755 - 97. ASTM; West Conshohocken PA; 1994 p.

American Society of Heating Refrigerating and Air Conditioning Engineers. (1972). 1972 ASHRAE Handbook - Fundamentals. Menasha, Wl, Banta Co. Inc.

Anonymous. (1993). "Vapor Barriers under Slat)s." Concrete Products. 96(3), 8.

Bordenaro, M. (1991). "Vapor Retarders Put Damper on Wet Insulation." Building Design and Constniction. 32(9), 74-77.

Carll, C. (2000). "Rainwater Intrusion in Light-Frame Building Walls." From Proceedings of the 2nd Annual Conference on Durability and Disaster IVIitigation in Wood-Frame Housing: November 6-8, 2000, Madison Wi, from www.toolbase.org. accessed 3 Jun 03.

Cash, K. (1993). "Where Roofe Meet Walls." Progressive Architecture. 74(2), 31-35.

Cushman, T. (1997). "Can Moisture Beat Housewrap?" Journal of U^t Construction, ^^{Q), 9,14.

Department of Energy. (2000). "Weather Resistive Bariers: How to select and install housewrap and other types of weather-resistive barriers." Technology Fact Sheet Series from the Office of Building Technology, State and Community Programs, Energy Efficiency and Renewable Energy, U.S. Department of Energy obtained from www.eere.energv.gov/buildings/documents/pdfs/28600.pdf accessed on 28 May 03.

Department of Energy. (2002). "Vapor Diffusion Retarders and Air Barriers." Consumer Energy Information: EREC Reference Briefs obtained from www.eere.energv.gov/consumerinfo/rfbrief5/bd4.html, accessed on 28 May 03.

Fisette, P. (1995). "Making Walls Watertight." Jouma/of L/gWConsfrurf/on, 14(3), 35-38.

Forest Products Laboratory (FPL). (2000). Tediline Durability: Controlling Moisture in Homes, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, from www.toolbase.org, accessed 3 Jun 03.

Guralnik, D. (1982). Webster's New World Dictionary: Second College Edition. New Yoric, Simon and Schuster.

Handegord, G. (1982). "Air Leakage, Ventilation, and Moisture Control in Buildings" in Moisture Migration in Buildings. ASTM STP 779; Philadelphia PA; 223-233.

Holladay, M. (2000). "Choosing a Sheathing Wrap." Journal of Ught Constniction, ^8{^■\), 79- 87.

Holladay, M. and Vara, J. (2000). "More Housewrap Performance Tests." Journal of Light Construction, 18(5), 13,16.

Insulation Contradors Association of America (ICAA). (2002). "Technical Bulletin: Use of Vapor RetarderTS." ICAP; Alexandria VA. Obtained from www.toolbase.org, accessed 3 Jun 03.

56

James, M. (2000). "Don't Staple Tyvek." Home Energy, UiS), 8.

JLC Staff Report. (1993). "The Last Word (We Hope) on Vapor Barriers: Answers to the most common questions about moisture migration through walls and ceilings." Journal of Light Consf/Tucffon, 11(11), 13-17.

Krogstad, N. and Weber, R. (1999). "Evaluation of Moisture Problems in Exterior Wall Assemblies" in Water Problems in Buildina Exterior Walls: Evaluation. Prevention, and Repair. ASTM STP 1352; West Conshohocken PA; 115-124.


Letter and response in "On the House". (2000). "Ceiling Vapor Barrier - Yes or No?" Journal of Ught Construction, 18(5), 21,23,24.



Lstiburek, J. (2000). Builder's Guide to Mixed Climates: Details for Design and Construction. The Tauton Press; Newton CT; 328 p.

Lstiburek, J. and Cannody, J. (1991). Moisture Control Handbook: New, low rise residential construction. Oak Ridge National Laboratory; Oak Ridge TN; 247 p.


McGinley, W. and van der Hoeven, R. (1999). "Envelope Analysis of Exterior Load Bearing Single-Wythe Partially Reinforced Hollow Clay Masonry Wall Systems for Residential Applications" in Water Problems in Building Exterior Walls: Evaluation. Prevention, and Repair. ASTM STP 1352; West Conshohocken PA; 199-214.

McDaniel, P. (2000). "Wrapping the House: Dos and Don'ts - Install it right, and housewrap works well to keep water out; lap it wrong and you are better off without it." Journal of Ught Construction. 18(6), 71-78.

O'Connor, T. and Johnson, P. (1995). "Stop that Water Vapor." Progressive Architecture. 76(12), 86-89.

Quiroutte, R. (1991). "Air and Vapor Barriers." Progressive Architecture. 72(9), 45-51.

Ramsey, C. and Sleeper, H. (1992). Construction Details from Architectural Graphic Standards. Eight Edition. ecSted by James Ambrose. New York, John Wiley & Sons, Inc.

Rogers, S. (1964). Thermal Design of Buildings. John Wiley and Sons, Inc.; New Yori<; 196 p.

Rousseau, M. (1990). "Air Barriers and Vapor Baniers: Are they of any use in low-slope roofs." Progressive Architecture. 71(7), 137-143.

Schroter, E. and Klein, K. (1999). "Considerations for Waterproofing of Wood-Framed Buildings" in Water Problems in Building Exterior Walls: Evaluation. Prevention, and Repair. ASTM STP 1352; West Conshohocken PA; 296-302.

57

Schuller, M, van der Hoeven, R., and Thomson, M. (1999). "Comparative Investigation of Plastic Properties and Water Permeance of Cement-Lime Mortars and Cement-Lime Replacement Mortars" in Water Problems in Building Exterior Walls: Evaluation. Prevention, and Repair. ASTM STP 1352; West Conshohocken PA; 145-158.

Shenwood, G. and Moody, R. (1989). Uaht-Frame Wall and Floor Svstems: Analvsis and Perfomnance. General Technical Report, FLP-GTR-59; U.S. Department of Agriculture, Forest Service, Forest Products Latwratory; Madison Wl; 162 p. Obtained from wvwv.nahbrc.org. accessed 3 Jun 03.

Spence.W. (1998). Construction Materials. Methods, and Technioues. Delmar Publications; NewYork;1195p.

Stein B. and Reynolds, J. (1992). Mechanical and Electrical Eouipment for BuiMings: 8th Edition. John Wiley and Sons, Inc.; New York; 1627 p.

Straube, J. (1998). "Moisture Control and Enclosure Wall Systems", Thesis for Dissertation from the University of Waterloo; Waterloo, Ontario, Canada; 408 p.

Straube, J. (2001). "The Influence of Low-Penmeance Vapor Barriers on Roof and Wall Perfonnance." Conference Paper presented at Proceedings of Themnal Performance of Building Envelopes VIII, Clearwater Beach, FL, 2-7 Dec 01. http://www.buildingsolutions.ca/Download%20Solutions.html, accessed on 31 Oct 02.

Straube, John F. (2002). "Moisture in the Buildings." ASHRAE Journal, January 2002. http://www.civil.uwaterloo.ca/beg/Downloads/ASHRAE%20Journal%20Jan%202002%20 Moisture.pdf. accessed on 31 Oct 02.

Straube, J. (2002). "Principles of Rain Control for Enclosure Design" from www.buildingsolutions.ca. accessed on 31 Oct 02.

Straube, J. (2002). "Vapor Barriers - Where and when do you need them?" http://www.buildingsolutions.ca/Download%20Solutions.html. accessed on 31 Oct 02.

Straube, J. and Burnett, E. (1999). "A Review of Rain Control and Design Strategies." Journal of Thermal Insulation and Building Envelopes, July 1999, 41-56. http://www.buildingsolutions.ca/Download%20Solutions.html. accessed on 31 Oct 02.

Suprenant, B. (1994). "Sub-Slab Vapor Barriers." Journal of Light Cons&uction, 12(8), Z7-39.

Trechsel, H., Achenbach, P., and Launey, S. (1982). "Moisture Control in Building Wall Retrofit" in Moisture Migration in Buildings. ASTM STP 779; Philadelphia PA; 148-159.

U.S. Forest Seroice. (1949). Condensation Control in Dwelling Construction by Forest Products Laboratory, Forest Service, U.S. Department of Agriculture in collaboration with the Housing and Home Finance Agency, Forest Products Laboratory; Madison Wl; 73 p.

Wettemnan, T. (1982). "Control of Moisture Migration in Light Frame Walls" in Moisture Migration in Buildings. ASTIV! STP 779; Philadelphia PA; 102-109.

Wilson, M. (1999). "Common 'Unique' Cavity Wall Flashing Problems: Mistakes Frequently Made, Their Resolution, and Presentations from Case Histories" in Water Problems in Building Exterior Walls: Evaluation. Prevention, and Repair. ASTM STP 1352; West Conshohocken PA; 240-252.

58

2.0 The Code Recommendations for Vapor barrier Implementation in Residential Construction: Do the recommendations make sense?

59

2.1 Introduction Vapor barriers are often misunderstood and misused materials within the building systems that

are utilized in residential construction. The standards as defined by the American Society of

Testing Materials (ASTM), and in the codes of the Council of American Building Officials, CABO:

One and Two Family Dwelling Code. 1995 Edition. Fourth Printing, and International Code

Council, International Residential Code: For One and Two Family Dwellings provide the industry

with certain recommendations and requirements of when, where, and if to utilize this material

within a structure's foundation, wall, and ceiling/roof cavity designs. The code recommendations

will be evaluated, and subsequent recommendations will be made for designers and builders who

reference/use/adhere to the code requirements to make decisions regarding the potential

implementation of vapor baniers for the specific location.

2.2 Standards defined by ASTIVI The ASTM standards, C755, define the vapor barrier's primary function within the wall system as

"to control the movement of diffusing water vapor into or through a permeable insulation system"

(ASTM, 1999). The diffused movement of vapor into and through a wall system follows one of

two flow patterns, unidirectional or reversible (ASTM, 1999). Vapor pressure difference is the

driving factor in determining how vapor barriers are to be used since the greater the pressure

differential, the greater the rate of diffusion through the assembly (ASTM, 1999). During the

design phase, the expected pressure differences should be realistic, not estimated, when

determining the vapor barrier requirements (ASTM, 1999). The general practices for building

cavity design as stated in ASTM cover air-conditioned structures, wood frame construction, and

the placement of the insulation in the wall system design.

ASTM defines unidirectional flow, as having a "water vapor pressure difference [that] is

consistently higher on one side of the system than the other" (ASTM, 1999). In cooler climates,

this vapor flow should include the design of the vapor barrier on the indoor, warmer, side of the

wall insulation. Reversible flow is defined as having a "vapor pressure [that] may be higher on

either side of the system, and it often changes with the seasons" (ASTM, 1999). Design for

reversible flow conditions do not greatly influence where in the wall system the vapor barrier

should be placed. The assumption is that drying will occur during the opposite season for which

the barrier was placed within the cavity.

If a membrane retarder material is to be used within the cavity, the ASTM recommends using a

retarder virith a lower permeance if a five-foot (1.5 meter) wide roll is used, or using a vapor

barrier/retarder with a higher permeance if a 20 foot (6.1 meter) width is installed (ASTM, 1999).

The reason for the permeance difference, dependent upon the width of the roll, is due to the air

penetration through the materials. The smaller width roll of membrane retarder would require a

60

lower permeance because there would be more laps, joints, and seams than the wider roll and

thus more air entrained vapor would potentially be allowed to pass through these potential

openings. Even with proper sealing of the laps, joints, and seams of the smaller width rolls,

perfect construction quality should never be relied upon for installation, especially since sealants

are prone to breakdown over time and the quality of installation cannot be relied upon to be "as

recommended" by the manufacturer (which most design specifications indicate). When designing

the cavity, low permeability insulation installed with sealed, vapor tight joints often acts like a

vapor barrier within the wall. A redundant vapor barrier system should be avoided, but is often

inadvertently constructed into the wall system design when a vapor barrier is purposefully used

and when the permeability characteristics of the other utilized wall system materials is not

researched or thoroughly understood.

The ASTM standards also recommend the implementation of an air barrier system within the wall

cavity (ASTM, 1999). The potential for condensation should be investigated when designing the

placement of the air barrier within the wall system (ASTM, 1999). The recommended placement

of the air barrier within the cavity is on the warm side of the insulation and should be installed in a

continuous, unbroken manner to prevent the uncontrolled movement of air through the wall

system, as previously discussed in the literature review. The air barrier is only as useful as it is

continuous.

A vapor barrier shouW be installed with all joints, holes, penetrations, and cuts being carefully

sealed with the recommended manufacturer specific sealants or tapes in order to maintain the

vapor diffusion resistance characteristics of the material (ASTM, 1999). The ASTM has defined

two recommended vapor barrier design practice principles, flow-through and moisture storage.

Flow-through design is supposed to eliminate the possibility of condensation within the insulation

and shouW include the use of a highly pemieable insulation within the cavity (ASTM, 1999). The

purpose of the high permeability insulation is to allow vapor to flow through the insulation and

condense, if the vapor is to condense, on the next lower permeable surface (ideally the vapor

barrier) within the system where the liquid would either be drained or removed through ventilation.

The moisture storage principle allows for some moisture accumulation within the system's

insulation, but the rate of accumulation is small and low permeability insulation should be used

(ASTM, 1999). The design utilizing the moisture storage principle assumes that moisture

condensation quantities virill not exceed the storage characteristics of the material before the

moisture is removed ft-om within the system.

When determining the vapor flow within the system, the calculations are very similar to the

calculations made to measure the heat flow through the wall system, see Section 1.3.2.3, pages

61

27-31. The formula, as provided by ASTM (1999), for calculating vapor flow through the wall

system is:

Vapor flow = Vapor pressure difference (between interior and exterior) Vapor flow resistance

The vapor pressure differentials in summer tend to cause vapor to flow in an inward direction, and

as such, a vapor barrier should be used on the outer side of the insulation and feeing the exterior

covering of the structure (ASTM, 1999). The ASTM guidance goes on to state Ihe vapor retarder

should still be located on the side of the insulation facing the interior of the building to control

vapor flow under the more severe conditions" (from the warm winter side of the system) (ASTM,

1999). The guidance continues, stating that if an impermeable insulation material is utilized, a

separate vapor barrier is not needed at all as long as the "joints (if any) are made impermeable by

suitable sealing methods" as recommended by the manufacturer (ASTM, 1999). The standard

includes a statement regarding residential construction and the implementation of a totally

separate system. The wall system must be designed for moisture that penetrates the retarder,

then moves into the insulation, and finally continues on to the outside through some means of

ventilation or forced air movement within the cavity (ASTM, 1999). The ASTM standards provide

design solutions/recomnrtendations to effectively handle all climatic conditions encountered in the

United States construction process, and they provide designers and builders with a clear

understanding of how to correctly utilize these materials in the wall systems.

2.3 CABO and iCC Code Summaries The current residential building codes, as published by the Council of American Building Officials

(CABO) and the International Code Councils (ICC), that have been investigated with regards to

the implementation of vapor barriers are for residential one and two family dwellings. The

applicable code sections from these references have been tabularized in summary form in Table

2.1 below.

Tabfe 2.1, Vapor barrier specific code summaries, adapted from CABO (1995) & ICC (2000)

Section Code Title Discussion

321 CABO "Moisture Vapor Retarders"

- Required in all frame walls and floors, and ceilings, not ventilated to allow moisture to escape. - Vapor barrier to be used on warm-in-winter side of thermal insulation with two (2) exceptions:


4.) Hot, humid climates: 67°F+ wet bulb temps for 3000+ hours or 73°F+ wet bulb temp for 1500+ hours during warmest six (6) consecutive months of year.

62

Section Code Title 1 Discussion

R322 ICC - In all framed walls, floors and roofe/ceilings comprising elements of building thermal envelope. - A vapor barrier shall be installed on warm-in-winter side of insulation with three (3) exceptions:


5.) Hot, humid climates: 67°F+ wet bulb temps for 3000+ hours or 73°F+ wet bulb temp for 1500+ hours during warmest six (6) consecutive months of year.

6.) Counties listed in ICC Table 1101.2, p.72-80 (summarized in report's table 2).

406 CABO "Foundation Waterproofing and Dampproofing"

- No discussion other than waterproofing applications and moisture barrier installation R406 ICC

409 CABO "Crawl Space" - When ground surface is treated with a vapor barrier, ventilation opening requirements may be reduced to 1/1,500 of the under-floor area, or - Ventilation openings may be omitted when continuously operating mechanical ventilation is provided at a rate of 1.0 cfm for each 50 fl^ of crawl space and the ground surface covered with a vapor barrier.

R408 ICC "Under-Floor Space" - Same two rules/exceptions as CABO, plus - Ventilation openings not required if ground covered with a vapor barrier, space is supplied with conditioned air, and perimeter walls are insulated.

505 CABO "Concrete Floors (on ground)"

- Vapor barrier with joints lapped at least six inches (6") shall be placed between slab and base course or prepared subgrade if no base course exists - Three (3) exceptions:

4.) Detached structures that are to be unheated (i.e., garages).

5.) Flatwork not likely to be enclosed and heated later (i.e., sidewalks, patios).

6.) As approved by building official. R506 ICC Exact words and requirements described in CABO

806 CABO "Roof Ventilation" Net free cross-ventilation area may be reduced to 1 to 300 with installation of vapor barrier (material with a transmission rate not exceeding 1 perni) installed on the warm side of ceiling.

R806 ICC Exact words and requirements described in CABO It should be noted that both CABO and the ICC state, with identical language, that "the total net free ventilating area shall not be less than 1 to 150 of the area of space ventilated except that the total area is permitted to be reduced to 1 to 300, provided at least 50% and not more than 80% of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 ft. above the eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents."

907 CABO "Built-up Roofing" - Vapor barrier to be installed between deck and insulation where average January temperature is below 45°F, or - Where excessive moisture conditions anticipated within the building.

R907 ICC - Nothing vapor barrier specific

63

Table 2.2, Adapted from information from ICC (2000): Section R322, Exception 3

State Number of counties exempted from wann-in-winter V.R. installation

North Carolina 16 of 100 counties

South Carolina 30 of 46 counties

Georgia 109 of 159 counties Florida All counties Alabama 47 of 67 counties Mississippi 64 of 82 counties Louisiana All parishes Arkansas 44 of 75 counties

Tennessee 2 of 95 counties Oklahoma 6 of 78 counties Texas 139 of 254 counties

The information that is presented in

Table 2.2 has been adapted and

condensed from the ICC, Section

R322, Table 1101.2, pages 72-80.

The exact counties/parishes listed

should be referenced when

designing or constructing a structure

in these states, and an exemption is

being sought for moisture vapor

barrier inclusion on the warm in

winter side of the insulation.

The two codes have similar intended

audiences (one and two family dwelling designers and builders), and the requirements with

regards to vapor barriers are nearly identical in both language and verbiage. Both of the codes

dictate to the designer or builder where the vapor barriers will be placed with the exception of the

section on concrete floors (on ground) where the provision, "or as approved by building official" is

included.

The requirements, as outlined in the codes, are feirly specific with regards of where, when, and

how to install vapor barriers vnthin the wall systems. The code requirements do not easily allow

proposals for acceptable alternatives by designers and builders who may be implementing

altemative approaches to construction.

2.4 What the codes should say...foundation, wall, and ceiling/roof 2.4.1 Foundation - slab The accumulation of moisture through the foundation/support elements (slab, basement, crawl

space, etc.) is the primary point of entry into residential construction assemblies (Suprenant,

1994). The incorporation of vapor baniers in the foundation design is only as effective as the

drainage mechanisms facilitate and allow. Designing proper drainage includes not only collecting

water, but also effectively moving water away from the structure so that it does not accumulate

and then migrate or be sucked up and into the wall system. The proper drainage requirements

are dictated by tiie specific site conditions. An attempt to cover the drainage requirements will

not be discussed at this time, other than to enforce the fad: that drainage is a critical element for

the design of the foundation system.

The placement of the sub-slab vapor barrier performs a dual role in the structure's moisture


64

structure's assembly (Lstiburek and Carmody, 1991). Capillary break points should be designed

into the entire foundation system for the many reasons discussed in the literature review Sections

1.3.2.2 and 1.3.3.1. The utilization of the vapor barrier to break capillarity and in these locations

provides the building with this first preventative measure in dealing with moisture and minimizing

the potentially harmful effects within the structure.




joints should be lapped at least six (6) inches, and the vapor barrier material should be as

impervious as possible to any breaks, punctures, or other such penetrations (Suprenant, 1994).

Any and all openings should be sealed with an appropriate sealing material as recommended by

the particular vapor barrier manufacturer. The role of the vapor barrier in this particular

application should be designed and constructed in a similar manner as an air barrier within the

wall system. The vapor barrier should be placed on top of, and in direct contact with, the

compacted subgrade material. Then, on top of the vapor barrier and below the concrete slab, a

three (3) inch thick layer of sand or varied sizes of gravel should be applied and lightly compacted

(Suprenant, 1994). Gravel is recommended over sand because gravel is less easily displaced

during the placement of the concrete slab and provides a consistently more uniform surface for

the slab's placement. A discussion with Joe Vinson, a residential house builder, reveals that this

layer is seWom used in residential construction because of the significant cost, and the perceived

benefits of incorporation do not outweigh the increased cost of installation (Vinson, 2003).

Special care and oversight should be taken during the concrete placement phase since the vapor

barrier's effectiveness is proportional to the integrity of the retarder membrane below. The usage

of a sand/gravel break between the vapor barrier and the concrete helps to prevent several

problenns that are often experienced when the concrete is placed in direct contact with the vapor

barrier. The break between the vapor barrier and the concrete allows for speeding up the time

between placement and finishing, helping to reduce the effects of cracking, improving the slab's

strength, and helping to eliminate slab curiing which may be experienced when concrete is placed

in direct contact with the vapor barrier (Suprenant, 1994).

The requirements as outlined in the CABO and ICC codes make recommendations for the

incorporation of vapor barriers in the on-grade sub-slab section that is in line and follows the

recommendations and guidance as discovered during the review of literature.

Graphical detail drawings of the slab-on-grade foundation may be found in Figure 2.1.

65

j. pBitfijetfreo ppAirJ Pipe

VAfoft- ft^vpgtef^ ^cofe-oc-eT)

Figure 2.1, Adapted standard slab-on-grade and basement detail from Ramsey and Sleeper (1992).

2.4.2 Foundation - crawl space

The next aspect of the foundation system that would need a vapor barrier, according to the

codes, is in the crawl space design that exists in many pier-post structures and other raised

structures including basements. The crawl space design is very similar to that of the sub-slab

vapor barrier. The same types of vapor barrier materials should be utilized in the crawl space

area, as in the slab-on-grade, but it may be necessary to cover the vapor barrier with either a soil

or gravel cover to prevent the vapor barrier from being moved. The ground cover vapor barrier

should follow the same design and installation requirements as an air barrier (i.e., seal and lap all

joints). The ground-cover vapor banier should be attached to the structure's support columns or

perimeter wall, if the space is enclosed. At all locations where the support columns or perimeter

walls intereect the wall system, the vapor barrier design should include a membrane to provide a

designated location to break capillary movement. The crawl space design should include a

properly designed drainage system to include grading to prevent ponding that may occur should

water pass through the crawl space. Ventilation of the crawl space is also necessary to help

prevent moisture from accumulating in an unvented space that could migrate up and into the

structure.

The codes state that "when [the] ground surface is treated with a vapor barrier, ventilation

opening requirements may be reduced to 1/1,500 of the under-floor area, or ventilation openings

may be omitted when continuously operating mechanical ventilation is provided at a rate of 1.0

cfm for each 50 fl^ of crawl space and the ground surface covered with a vapor barrier" CABO,

66

1995 and ICC, 2000). The code allowed reduction does not follow the literature

recommendations that were reviewed in the previous chapter. The purpose of the vapor barrier

within this space proves to be very effective at combating the accumulation of moisture within the

substructure that could then be pulled or transported up and into the structure. The opinion of the

author is that maintaining the original recommended ventilation requirements in the crawl space,

with or without a vapor barrier, is a necessity for residences. Ventilation in this semi-enclosed

space is important should this space become wet. Drying can be facilitated through proper

ventilation and moisture accumulation can be minimized and removed.

Graphical detail drawings of the crawl space foundation may be found in Figure 2.2.

__V«^g,b«gM^

t>il«*«>Ti«M

f. scpB6NS> ^*^'T

Figure 2.2, Adapted standard crawl-space detail from FPL (1949) and Ramsey and Sleeper (1992).

2.4.3 Foundation - basement

The design of the basement walls with regard to moisture is another problematic area that

changes with regard to the particular building design. Basement slab design should follow the

same design guidance that was provided in Section 2.4.1 with respect to sub-slab design. Due to

the presence of high quantities of construction water that migrate out of the concrete basement

walls over the first six (6) plus months, it is recommended that the basement walls not be

insulated or finished during this time period. Allowing the basement walls to cure and expel this

67

construction water from the structure will help eliminate many of the problems that finished

basements are prone to encounter. A preventive measure for the basement footings is to design

a capillary break using a vapor barrier between the footing and the vertical basement wall

(Lstiburek, 2000). Other than the standard dampproofing and waterproofing applications applied

to the exterior surfaces of the basement walls, no other vapor barrier treatments are needed or

required in these systems since the drying characteristics of the wall will vary significantly with the

seasons. A vapor barrier would not facilitate the flow-through principle that should be utilized in

basements. It should be noted, though not the opinion of the author, that the literature reviewed

does recommend following the example of what was done above grade should be implemented

below grade (i.e., if a vapor barrier was incorporated on the inner portion of the above grade wall

then one should be used at the same location in the below grade basement wall system).

Graphical detail drawings of the basement foundation may be found in Figure 2.1 in Section 2.4.1

above.

2.4.4 Walls The use of a vapor barrier in a wall assembly is an often confusing and wrongly accomplished

detail that may lead to many moisture problems within assemblies. The application of the vapor

barrier within the wall system design is greatly dependent upon where the structure is climatically,

the orientation of the wall, and the wall system design. It should be noted that when a vapor

barrier is installed incorrectly or redundantly the vapor barrier might become a vapor trap. Many

materials behave like a vapor bamer within the wall cavity and all material permeance ratings

should be investigated before designing or constructing the wall. ASTM states, "for practical

purposes it is assumed that the permeance of an adequate retarder will not exceed 1 perm,

although at present this value may be adequate only for residential construction" (ASTM, 1999).

The climatic regions for residential design that this report will follow are in line with the ones

presented by Lstiburek and Carmody and are labeled as heating climates, mixed climates, and

cooling climates. The climatic regions are identified in Table 1.1, Section 1.3.1, of the literature

review, but the characteristics are resummarized as follows:

• Heating dimate is defined as an area that has 4000+ heating degree-days (Lstiburek

andCamriody, 1991).

• Mixed climate is an area that has up to 4000 heating degree-days (Lstiburek and

Carmody, 1991).

• Cooling climate is defined as an area that has 67°F or higher WB temperatures for



Carmody, 1991).

68

The implementation of a vapor barrier within the wall system of the residence built in a heating

climate should follow the guidance that a vapor barrier should be installed on the inside of the

wall insulation. The recommendations made in both the CABO and ICC codes follow this

guidance fairly closely, although the number of heating degree-days varies slightly. The specific

wall system design should be analyzed in more detail by utilizing psychrometric charts and

investigating how the wall system temperature drops at each material change to determine where

and if to incorporate a vapor barrier. The specific points where the dew point is reached within

the cavity should be determined, and the vapor barrier incorporated as appropriate in a heating

climate for each specific wall design.

A vapor barrier within the cavity of a wall system built in a cooling climate, or one which is

typically classified as a hot and humid weather location, should place the vapor barrier on the

outside (towards the exterior) of the wall system's insulation. Although the conditions for these

locations would qualify as an exemption in the CABO and ICC codes (with the same slight

deviation in the specific number of wet bulb temperatures) for placement on the warm-in-winter

side, the codes recommendations are vague as to exactly where the vapor barrier should be

placed within the wall system. The ICC does provide a very thorough listing of counties within

each of the states in the United States that would qualify under this code exemption. Both codes

should state that the vapor barrier should be located on the side of the insulation facing the

structure's exterior if any of the exemption rules qualify.

The incorporation of a vapor barrier in a mixed climate is the area that remains most vague and

for the most part neglected in the code requirements and in the literature reviewed. The primary

difference for determining whether to use a vapor barrier or not depends upon understanding the

nature of vapor movement and the potential for drying within the specific wall system design. The

ASTM recommends utilizing a flow-through design approach, and this approach closely follovre

other research and is logical for combating the moisture problem. The flow-through design

approach follows the principle discussed in the literature review. Section 1.3.5, pages 41 - 47.

This approach acknowledges the fact that wetting will occur from one side of the wall system

during one season, and that the wall system vrill allow drying in the next season from the opposite

side. Following the flow-through approach for the mixed climate region of the country is the most

logical approach from a design perspective. The design for these types of wall systems must be

closely examined and investigated because the potential for creating a redundant or inadvertent

vapor barrier system within the wall cavity creates the ideal environment for problems associated

with vapor accumulation, such as mold, mildew, and ultimately decay.

69

The codes need to make recommendations for vapor barriers within the wall systems that are

more climatically specific and address the permeability issues of the other materials that are

utilized in the wall systems. Redundant vapor barrier systems are often inadvertently installed

during construction, preventative maintenance, and renovation. Several examples of the

incorporation of unintended vapor barriers include multiple, as few as three, coats of paint (non-

vapor retarder latex specific), two coats of acrylic latex paint with premium latex primer

underneath, vinyl wall coverings or wallpaper, the various adhesives used with wall coverings, foil

faced plywood/OSB, bitumen/wax Impregnated kraft paper, aluminum or paper faced fiberglass

roll insulation, and using 1/4-inch Douglas fir plywood with exterior glue, etc (Lstiburek, 2000;

ICAA, 2002; Spence, 1998; Bordenaro, 1991; Maness 1991; Lotz, 1998; Lstiburek and Carmody,

1991; Forest Produds Lab, 1949; and DoE, 2002).

The recommendations for several wall section systems are summarized in Table 2.3 below. The

discussed wall sections incorporate the following components: wood siding, aluminum siding,

brick veneer, plaster veneer, and concrete shell. The various sections will be described with

generic section solutions in the "Model Wall Section/Type" column. The respective climatic area

columns will be used to discuss where the vapor barrier or other wall section revisions should be

incorporated if one of these sections were utilized in the particular climatic area.

70

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Graphical detail drawings of the wall section described above may be found in Figures 2.3 to 2.6.

}:■

(g)—r: . .i

i

5 6yF«UM fc<qdj2t?

Figure 2.3, Adapted standard stucco veneer detail from Ramsey and Sleeper (1992).

Figure 2.4, Holistic House Wall Section provided by Yvan Beliveau.

72

Fiaure 2.5, Adapted standard wood-sidina detail from Ramsey and

c;. MPTAI-Ties'

E- SHBA-miHtf-

6-. ^psoH fcevytt>

Figure 2.6, Adapted standard brick veneer on light-wood frame detail from Ramsey and Sleeper (1992).

73

2.4.5 Roof/Ceiling

The use of a vapor barrier in the roof/ceiling components of the assembly is effective and

recommended as a means of being able to reduce the ventilation requirements in this part of our





making a determination for when to utilize a vapor bamer.

The United States Forest Service published a pamphlet in 1949 that clearly explained the vapor

barrier requirements according to the various climatic regions of the United States and the

varying types of roofs (flat, gable/hip with no occupancy, and gable/hip with occupancy). The

1949 pamphlet's format served as the template for Table 2.4 that was developed to help explain

the roof design recommendation in this report.

Tabre 2.4, Various Roofing V.B. Applications According to Climate

Roof Type Flat Roof

Roof with Attic

Cathedral Celling

Heating Climate V.B. may be installed

between deck and insulation, if design calculations prove its necessity

- Super low permeance plastic sheet V.B. & air barrier designed between built-up roofing and insulation In 8000+ heating degree day climates - Higher permeance V.B. & air barrier designed between built-up roofing and Insulation - Circulation/venting must be provided - Design calculations must be utilized to determine inclusion or exclusion - V.B. installed below the insulation (in the interior side of insulation) - Ventilation at the eave and ridge vented - Design calculations must be utilized to determine inclusion or exclusion

Mixed Climate - V.B. should be installed between deck and insulation, if the winter temps are as discussed in codes and design calculations necessitate incorporation - Higher pemieance V.B. & air barrier designed between built-up roofing and insulation - Circulation/venting must be provided - Design calculations must be utilized to determine inclusion or exclusion

- V.B. installed below the insulation (in the interior side of insulation) - Ventilation at the eave and ridge vented - Design calculations must be utilized to determine inclusion or exclusion

Cooling Climate V.B. not needed

- V.B. should not be used in this climate - Air circulation/venting sufficient in hot, dry environments - Air circulation/venting should be avoided due to high moisture concentrations In hot, humid environments - Air barrier designed to prevent air leakage

- V.B. not necessary - Ventilation requirements same as attic space and should occur at eave and ridge if ventilated

Note: The CABO and ICC codes state, "[n]et free cross-ventilation area may installation of vapor retarder (material with a transmission rate not exceedng side of ceiling."

be reduced to 1 to 300 with 1 perm) installed on the warm

74



system. The only firm conclusion with regards to the inclusion or exclusion of vapor barriers in

the roof design is to calculate the specific point where the dew point is reached within the roof

system. The influence of air movement must be considered and the potential for drying through

air movement to the interior or exterior of the roofing system materials. The designer must also

be cognizant of the fact that if a vapor bamer is included and the roof develops a leak, the vapor

barrier could behave as a vapor trap and cause the system to retain the water by not allowing it to

escape.

The codes state that the "[n]et free cross-ventilation area may be reduced to 1 to 300 with

installation of vapor barrier (material with a transmission rate not exceeding 1 perm) installed on

the warm side of ceiling" (CABO, 1995 and ICC, 2000). The allowed reduction does not appear

to make any sense for the climatic areas where roof ventilation is required. One of the purposes

of roof ventilation is to allow the space to dry out should the space below the roof become wet,

and reducing the ventilation requirements would hamper this needed process. The opinion of the

author is that the codes allow reduction of ventilation within the roof cavity is not recommended.

The ventilation of the roof is necessary in effectively combating moisture accumulation in a

heating area but not in a cooling environment.

Graphical detail drawings for the roofing applications described above may be found in Figures

2.7 to 2.9 below.

^•SH6A.TH1NS-

F- SflFFtT

H. Bu>c}£JN6-

OiM&T^ BxUJQ-r 0<tAA\i(r CUV^/SXB .

Fiaure 2.7. Adanted standard roof with attic detail from Ramsey and Sleeper M992^. — 75

f. ^2AFret2-

see-T*«ei-c sv^ft^w^-

Figure 2.8, Adapted standard flat-roof detail from Ramsey and Sleeper (1992).

aitm^-6)UGf=r HdH*flc?

A.ASfHAUT m'^MU^

i, fSAPTCtt

Figure 2.9, Adapted standard cathedral ceiling detail from Ramsey and Sleeper (1992).

76

2.5 Summary While the specifics are not provided for all situations that can be encountered in the building

systems of the United States, several common and general details are discussed with areas of

inclusion and exclusion noted. The standards as defined by the American Society of Testing

Materials (ASTM), and the codes of the Council of American Building Officials, CABO: One and

Two Family Dwelling Code. 1995 Edition. Fourth Printing, and International Code Council,

International Residential Code: For One and Two Family Dwellings provide the industry with the

recommendations and requirements of when, where, and if to utilize these materials in our

structures. Some, but not all, of the code recommendations make sense in light of the literature

that was reviewed, but where the codes do not make sense recommendations are provided.

The author has come to the conclusion that regardless of the literature that has been reviewed,

the subject of vapor barriers remains a greatly misunderstood and confusing building material.

Builders ridicule the literature and construct out of experience and not what either the literature or

simple calculations reveal. It is the opinion of the author that vapor barriers should be used in

heating climates at all locations within the structure's foundation, wall, and roof assemblies. The

implementation of a vapor barrier should be included within the foundation and wall assemblies of

all structures in a cooling climate, but that the specific application in the roof remains one area

that depends upon the specific, detailed structure's design but specific recommendations have

been made in the roofing section for several roof types.

While this report's specific aim is to clarify and determine when, where, and if to utilize a vapor

barrier in the mixed climate area, the topic remains quite variable and specific depending upon

the design, materials utilized, and orientation of the structure. A vapor barrier is recommended

for the foundation and roof assembly for all structures in this climate, but the when and where to

utilize a vapor barrier within the wall remains less clear. The literature states that a vapor barrier

is not necessary within the wall in a mixed climate. The literature also states that the principles of

flow-through design are to be utilized in this area, and for this reason an air barrier should not be

incorporated into the design. The flow of air through the wall is the driving agent of moisture into

and out of the wall assembly depending upon the season. The principle of flow-through design

allows wetting during one season and drying during the opposite that should effectively handle

moisture within the cavity. The flow-through principles should effectively control moisture in the

mixed climate without the needed incorporation of a vapor barrier into the wall system. It is the

opinion of the author that a vapor barrier is not needed for the mixed climate. A vapor barrier

may be used in the wall section, and should be placed in the same position as in the cooling

climate wall. The benefits of utilizing a vapor barrier in the mixed climate do not outweigh those

for not using one. The added cost, without benefits, should help make the decision easier not to

use a vapor barrier in a mixed climate.

77

2.6 References Cited American Society of Testing and IVIaterials (ASTM). (1999). ASTM Standards in Building Codes,

Volume 2: Designation C 755 - 97. ASTM; West Conshotiocken PA; 1994 p.

Code of Federal Regulations (CFR). (2001). "3280.504 Condensation Control and Installation of Vapor Retarders." Code of Federal Regulations: 24CFR3280.504. U.S. Government Printing Office via GPO Access from www.hud.qov:80/offices/cpd/energvenviron/enerav/iawsandregs/reas/subpartf/3280504. accessed on 3 Jun 03.

Council of American Building Officials. (1995). CABO: One and Two Family Dwelling Code. 1995 Edition. Fourth Printing. CABO; Falls Church VA; 350 p.

Insulation Contractors Association of America (ICAA). (2002). "Technical Bulletin: Use of Vapor Retarders." ICAP; Alexandria VA. Obtained from www.tooibase.org. accessed 3 Jun 03.

Intemational Code Council. (2000). International Residential Code: For One and Two Family Dwellings. Intemational Code Council; Falls Church VA; 566 p.

JLC Staff Report. (1993). "The Last Word (We Hope) on Vapor Barriers: Answers to the most common questions about moisture migration through walls and ceilings." Journal of Light Construction, ^'i{^^),^3-17.

Letter and response in'On the House". (2000). "Ceiling Vapor Barrier - Yes or No?" Journal of Ught Construction, 18(5), 21,23,24.

Lstiburek, J. (2000). Builder's Guide to Mixed Climates: Details for Design and Construction. The Tauton Press; Newton CT; 328 p.

Lstiburek, J. and Carmody, J. (1991). Moisture Control Handbook: New, low rise residential constmction. Oak Ridge National Laboratory; Oak Ridge TN; 247 p.

Stein B. and Reynolds, J. (1992). Mechanical and Electrical Equipment for Buildings: 8th Edition. John Wiley and Sons, Inc.; New York; 1627 p.

Suprenant, B. (1994). "Sub-Slab Vapor Barriers." Jouma/of L/gWConsfr-ucfton, 12(8), 37-39.

U.S. Forest Service. (1949). Condensation Control: in dwelling constmction by Forest Products Laboratory, Forest Service, U.S. Department of Agriculture in collaboration with the Housing and Home Finance Agency, Forest Products Laboratory; Madison Wl; 73 p.


78

3.0 WUFI Data Results Summary

79

3.1 Background of Software Program, Initial Assumptions, and Limitations WUFI, Warme-und Feuchteransport Instationar (Transient Heat and Moisture Transport), is a

program that was developed as part of two student dissertations at German Universities in 1994

and 1995. Tiie Oak Ridge National Laboratory is the point of contact for the software in the

United States. The WUFI software program that was used for the data interpretation was the

"Student Version" software. The WUFI program is an effective testing tool for the analysis of

Thermal Conductivity, Diffusion Resistance, Liquid Transport, Total Water Content in the

construction and in the individual components. Solar Radiation calculations, Air Temperatures

changes, and the Relative Humidity level changes at various component locations within the wall

system. The WUFI program does allow the user to model the different directional conditions that

the wall system would be exposed to by allowing the user to select the direction of the wall, such

as North, South, East, and West. The user can run the test wall through each different direction

to see the directional impact that the building systems will experience.

The "Student Version" software program has several data and program output limitations. The

program does provide the end user with the information necessary to calculate the dew point but

stops short of plotting the dew point for the respective data runs. In addition, the software

evaluates the effects of diffusion through materials but does not consider the effects of air

movement through the wall system. As the title states, the point of interest is in "Transient Heat

and Moisture Transport," but the moisture transport is limited to transport through diffusion, which

as the literature review stated, is the mechanism that transports the least amount of moisture

through the building assembly. The inputs for the wall systems that could be tested were limited

to being able to test vertical wall assemblies only, so no roof or foundation systems could be

tested or evaluated. The library of components that the "Student Version" of the software offered

was extremely limited, and the only assemblies discussed in the previous sections that could be

tested were for a wood (spruce) siding model and a brick veneer model.

The major assumption that was made with regards to the WUFI data is that air movement, not

vapor diffusion, is the major transport method to be dealt with in our wall systems. The WUFI

student version software program evaluates the effects of vapor diffusion through the wall system

but does not address the effects of air movement, which the literature reviewed stated is the

predominant means of transporting vapor through the building systems. Air penetrates the

building system and allows vapor to enter the building materials through the joints between

materials, at the corners, through inlets and outlets, at the top plate, and sill plates. Once air

enters the wall system, the potential for condensation to form within the cavity is created at the

next coldest location once the dew point has been attained. The wall section evaluations that the

WUFI program performs are similar to those discussed in Section 1.3.2.1.2, Perfect Barriers, and

as such do not consider any of the effects that the quality of the construction detail has on our

80

buildings. The construction detail that Is done correctly and has no openings for air to move

through the wall components would behave in this manner, but that level of construction cannot

be attained throughout the entire building and therefore air movement should still be considered.

As such, the effects of air movement through the wall system were not modeled or considered

discussion of the WUFI results that follow in the next few sections, but these effects still need to

be considered.

The data result interpretations were made utilizing the assumption that air movement, not vapor

diffusion, transports the majority of moisture vapor in our wall cavities. The results that were

obtained from the WUFI software Indicate this assumption to be true. The results with regard to

air transported moisture vapor remains unproven/untested in this report's result section that

follows. This assumption was validated by the WUFI results because the relative humidity levels,

due to vapor diffusion, rarely rose high enough at the expected dew point locations to reach the

dew point and create liquid condensate. The monitor positions 2 and 3 within the modeled walls

are the theoretical points vtdthin the wall cavity where condensate (caused by the attainment of

the dew point on the next cold surface) would be expected to form within the wall. The theory of

where condensate typically occurs within the wall systems helped determine the likely points

within the wall cavity to establish and nrranitor the relative humidity levels.

The software program also has several output limitations that were observed during the test runs

and the subsequent data interpretation process. The outputs for the "Student Version" of the

program were quite limited and would only allow the end user to view preprogrammed outputs

that were in graphical form and did not allow any tabular data outputs or other forms of

customization. Sample manual dew point calculations utilizing the psychrometric charts from

Stein and Reynolds, Mechanical and Electrical Equipment for Buildings: 8th Edition, utilizing the

relative humidity and temperature readings that WUFI generated have been accomplished and

may be seen found in Figures 3.2 - 3.7 at the end of this section (Stein and Reynolds, 1992).

3.2 Model Development and Data Interpretations Once the software program had been experimented with and the program's limitations were

better understood, the code system. Table 3.1, was developed to maintain control over the

numerous data samples that were taken. The purpose of utilizing the WUFI program became to

test the findings from the literature review that vapor moved by air transported mechanisms is the

predominant issue within the wall cavity. Diffusion through the wall materials is not the primary

concem because the amount of vapor moved by diffusion is negligible when compared to air

transport.

81

Table 3.1, WUFI File Data Key

1-2-3-4-5-6-7.pdf

Block 1 What is the wall section? 1 - Brick and 2 - Spruce

Block 2 VB - Vapor Barrier or NVB - No Vapor Barrier

Block 3 Where is structure located? R - Roanoke, M - Minneapolis, and NO - New Orleans

Block 4 What month the data was run for? 1 - January, 4 - April, 7 - July, and 10 - October

Block 5 What is interior climate control? AC - Air Condition and NAC - No Air Condition

Blocks Data plot number (1 or 2)

Block 7 Where is the vapor barrier location? 1 - New Orleans and 2 - Minneapolis

For example, a 1-VB-R-4-AC-1-2 means that the PDF file is for a Brick veneer structure, with a

vapor barrier, in Roanoke, during April, in an air conditioned space, that the plot was the first one,

and that the vapor bam'er location was in the same location that the vapor barrier would occupy

in Minneapolis (\.e., between the gypsum board and the insulation).

The tests run, using the WUFI program, created 112 data samples for the two exterior wall cover

systems. The tests were conducted only for the months of January, April, July, and October with

the belief that these tests would provide enough data to show how the "vapor barrierTno vapor

barrier" assemblies behaved to test the conclusions that were drawn in the previous sections for a

heating climate (Minneapolis), a nnixed climate (Roanoke), and a cooling climate (New Orleans)

with respect to vapor

diffusion. The wall section

that was utilized in the 112

tests is as diagrammed in

Figure 3.1.

1 The program only allowed for

the monitoring of four

positions per test run, and the

exterior and interior positions

were default positions

established in the program.

The other two selected

positions were placed within

the wall section at the most

likely accumulation points for

vapor/condensation once the dew point is reached within the cavity

i 3 4

V

T

1 Monitor positions in program

• 50 mm air layer

' Brick/Spruce

"5mm air layer

' 60 minute building paper

-Exterior grade plywood

-Fiber glass

"Gypsum wallboard

"50 mm air layer

5 mm polyethylene vapor barrier position

New Orleans Minneapolis V.B. VB.

Figure 3.1, WUFI wall section utilized in the tests

82

The use of a five-millimeter polyethylene vapor barrier was selected since this vapor barrier

presented the wall section to the vapor retarding material with the lowest permeability and least

capacity to store vapor. The other alternative for the vapor barrier was to utilize a "smart vapor

barrier" which is a wax or asphalt impregnated building paper that retains water in some seasons

and dries during the opposite one. The "smart vapor barrier" was not used due to its capacity to

retain water and subsequently dry. The two positions for the vapor barriers writhin the wall section

are the two expected vapor barrier installation points utilized in the construction industry and in

the literature reviewed. The New Orleans positioned vapor barrier was placed on the exterior or

warm side of the insulation due to the high temperatures and high levels of humidity to be

experienced from the exterior and the use of air conditioning in the interior. The Minneapolis

positioned vapor barrier was placed on the interior side of the insulation to account for the cold

exterior temperatures and the high use of heating systems by the occupants for the majority of

months in the year.

3.2.1 New Orleans Data Results The test results for the New Orleans wall sections without a vapor barrier, both bricl< and spruce

models, had nearly identical results utilizing the WUFI software. The only noted variations within

the wall sections occunred within the monitored position 2, and the relative hunrwdity levels did not

vary more than approximately ±2% relative humidity. The relative humidity levels did not change

significantly during the course of a one-month test run. The noted changes within the wall section

can be attributed to the diffusion characteristics of the materials, and since the exterior materials

are relatively the same, the amount of infiltration within the two different cavities appears to be

similar. The relative humidity levels at both monitor positions 2 and 3 were similar when

compared to the same positions in the vapor barrier and no vapor barrier models.

The test results for the New Orleans wall sections with vapor barrier were nearly identical to the

no vapor barrier nrrodels when compared during the month of January, when the exterior relative

humidity levels were the lowest for the year. The test results during the month of April, when

compared to the same month's model without a vapor barrier, were nearly identical. The relative

humidity levels rose quite significantly when compared to the conditions during January, but

remain consistent with the no vapor barrier model during the same time period. The relative

humidity levels at both monitor positions 2 and 3 were similar when compared to the same

positions in the vapor barrier and no vapor barrier models.

The July test results for the New Orleans wall section with a vapor barrier compared to the

section without a vapor barrier showed very similar results during the first 20 days of the test run.

The exterior relative humidity levels were extremely high when compared to the two previous

83

months' test run data. The data that was monitored at monitor position 2 showed a decline in the

relative humidity levels in the vapor barrier wall section. The deviation at the 20-day period is

approximately 5% lower when compared to the no vapor barrier model. The respective

deviations at the 25- and 30-day periods are approximately 5% lower at each of the periods and

show a significant drop in the relative humidity. These data results con'elate to less opportunity for

condensate to form, and thus less opportunity for mold and fungi propagation. The monitor

position 3 remains identical for both vapor barrier and no vapor barrier systems with regards to

relative humidity.

The October test results show relative humidity levels that are higher than both the January and

April test runs, but significantly less than those experienced and tested during the July run. The

data obtained from monitored position 2 within the wall section shows a slight decline at the 25-

and 30-day periods. The drop in relative humidity levels for the vapor barrier wall when

compared to the no vapor barrier wall is approximately 5% less per 5-day period. The monitor

position 3 relative humidity levels remain identical for both of the tested systems.

Table 3.2, New Orleans summary of relative humidity data results from WUFI when compared to the no vapor barrier model results

New Orteans VB placement

Monitor 2 Monitor 3

January - Spruce Model ~ ~

April - Spruce Model ~ ~

July - Spruce Mode! t ~

October - Spruce Model t —

The New Orleans test data graphs can be found in Appendix 1 at the end of the report.

3.2.2 Minneapolis Data Results The test results for the Minneapolis brick and spruce wall sections with no vapor barrier showed

very slight to no deviation utilizing the WUFI software. The deviations noted were all seen at

monitor position 3 within the wall section with only one noted change occurring at monitor position

2. The first relative humidity deviation at monitor position 3 occurred in January around the 20-

day point and was approximately 5% higher in the spmce model. The relative humidity levels in

the spruce model at the 25-day point was approximately 3% higher, and the 30-day period saw a

rise of approximately 5%. The April test run did not reveal any relative humidity level changes at

monitor position 3. The July test run revealed relative humidity level changes at monitor position

2 beginning at day 10. The change at day 10 showed an increase in relative humidity on the

spruce model compared to the brick model of approximately 3%. The relative humidity level

84

changes for the 15-, 20-, 25-, and 30-day periods showed a rise of approximately 5% per 5-day

period in the spruce model. The rise in the relative humidity levels during July in the spruce

model is very lilêiy to be attributable to the moisture storage and diffusion characteristics of the

spruce. The monitor position 3 in July does not show any significant change between the two

models. The October test result data does not show any significant changes in either the monitor

2 or 3 positions. The test run data for the spruce and brick wall sections with vapor barrier show

nearly identical test results. The slight deviations were noted, but the change was approximately

±1% relative humidity at only a very few data points and do not appear significant enough to

specifically draw attention to those points.

The January test data, both spruce and brick models, comparing the no vapor barrier to the vapor

barrier models reveals that the relative humidity level rises approximately 2% in the no vapor

barrier model at monitor position 2 at the 10-day period. The relative humidity level increase

continues for the 15-, 20-, 25-, and 30-day periods at monitor position 2 with the increases being

approximately 2%, 4%, 5%, and 8%, respectively. The monitor position 3 data results show that

the relative humidity levels are significantly lower for the no vapor barrier models at the beginning

of the test run. At the end of a 5-day period, the relative humidity level for the vapor barrier wall

at monitor position 3 is approximately 15% higher. The relative humidity levels for the 10-, 15-,

20-, 25-, and 30-day periods show increases of approximately 20%, 25%, 15%, 10%, and 25%,

respectively.

The April test data, for both the spruce and brick veneer models, comparing the no vapor barrier

to the vapor barrier models reveals that the relative humidity level rises approximately 1% in the

no vapor barrier model at monitor position 2 at the 10-day period. The relative humidity rise

continues for the 15-, 20-, 25-, and 30-day periods at monitor position 2 with the increases being

approximately 2%, 3%, 5%, and 5% respectively. The monitor position 3 data results show that

the relative humidity levels are lower for the no vapor barrier models at the beginning of the test

run. At the end of a 5-day period, the relative humidity level for the vapor barrier model at monitor

position 3 is approximately 12% higher. The relative humidity levels for the 10-, 15-, 20-, 25-, and

30-day periods show increases of approximately 10%, 5%, 8%, 2%, and 5%, respectively.

The July test data, for both the spruce and brick models, comparing the no vapor barrier to the

vapor barrier models reveals that the relative humidity level decreases approximately 1% in the

no vapor barrier model at monitor position 2 at the 5-day period. The relative humidity level

decrease continues for the 10-, 15-, 20-, 25-, and 30-day periods at monitor position 2 with the

decreases being approximately 5%, 10%, 12%, 15%, and 20%, respectively. The relative

85

humidity levels for monitor position 3 in the no vapor barrier and vapor trarrier wall does not

reveal any significant deviations between the test data.

The October test data for both the vapor barrier and no vapor barrier models reveal identical

relative humidity levels for both wall systems at monitor position 2 in the cavity. The data for

monitor position 3 shov^ a general increase in the relative humidity levels for the no vapor barrier

model beginning at the 5-day period writh a noted increase of approximately 4%. The increases

for the 10-, 15-, 20-, 25-, and 30-day periods are approximately 1%, 1%, 10%, 8%, and 3%,

respectively.

Table 3.3, Minneapolis summary of relative humidity data results from WUFI when compared to the no vapor barrier model results

Minneapolis - Brick and Spruce models VB placement

Monitor 2 Monitor 3

January 4 t April 4 t July t —

October — f The actual test run data for the Minneapolis wall sections may be found in Appendix 2 at the end

of the report.

3.2.3 Roanoke Data Results The test results for the Roanoke brick and spruce wall sections without a vapor barrier had only

very slight to no deviations noted utilizing the WUFI software in the months of January and April

for monitor positions 2 and 3. However, the July data results show a substantial relative humidity

level decrease in the brick model compared to the spruce siding model beginning at day 5 at

monitor position 2. The relative humidity level at monitor position 2 decreases for the 5-, 10-, 15-,

20-, 25-, and 30-day periods are approximately 2%, 4%, 10%, 12%, 15%, and 18%, respectively.

The relative humidity levels for the monitor position 3 during July were identical for the vapor

barrier and no vapor barrier models. The relative humidity levels for position monitors 2 and 3

during October were identical for the vapor barrier and no vapor banier models.

The test results for the brick wall sections, vapor barrier and no vapor barrier, for the month of

January at monitor position 2 show identical relative humidity levels for the vapor barrier located

in the New Orleans vapor barrier placement. The monitor position 2 relative humidity levels for

the Minneapolis vapor barrier placement are identical until the 15-day period, which then shows a

decrease in relative humidity of approximately 1%. The 20-, 25-, and 30-day data periods show a

decrease in relative humidity of 2%, 4%, and 5%, respectively. The relative humidity levels for

the New Orieans placed vapor barrier at the monitor position 3 is identical to the no vapor barrier

86

wall. The Minneapolis placed vapor barrier at the monitor position 3 shows a fairly significant

increase in relative humidity levels when compared to the no vapor barrier wall system. The

relative humidity increase at the 5-, 10-, 15-, 20-, 25-, and 30-day periods is approximately 5%,

10%, 8%, 12%, 10%, and 15%, respectively.

The April data results for the brick wall at monitor position 2 remains nearly identical for the New

Orieans placed vapor barrier as in the no vapor barrier model. The Minneapolis placed vapor

barrier model shows a relative humidity decrease at the monitor position 2 beginning at the 10-

day period of approximately 1%. The decreases for the 15-, 20-, 25-, and 30-day periods is

approximately 3%, 4%, 5%, and 4%, respectively at monitor position 2. The monitor position 3 for

the New Orleans placed vapor barrier remains identical to the no vapor barrier model. The

monitor position 3 for the Minneapolis placed vapor barrier shows mixed levels of increase and

decrease starting at the 5-day period. The data shows slight decrease in relative humidity in the

vapor barrier model at the 5-day period, an increase of approximately 5% in the vapor barrier

model at each of the 10- and 15-day periods. The model shows the relative humidity level rising

approximately 4% higher in the no vapor barrier wall compared to the vapor barrier model at the

20-day period, and this rises to approximately 10% for the 25-day period. The vapor barrier

model's relative hunrudity level rises to approximately 4% higher than the no vapor barrier model.

The July data for the brick wall at monitor position 2 remains identical for the New Orieans vapor

barrier position and the no vapor barrier walls. The monitor position 2 for the Minneapolis placed

vapor barrier remains significantly higher than the no vapor barrier wall. The relative humidity

levels at the 5-, 10-, 15-, 20-, 25-, and 30-day periods are increased approximately 3%, 5%, 10%,

15%, 20%, and 23% when compared to the no vapor barrier system. The monitor position 3

reading for the New Orieans placed vapor barrier is identical to the no vapor barrier wall. The

monitor position 3 reading for the Minneapolis placed vapor barrier is significantly lower in the

vapor barrier wall during the 5-, 10-, 15-, and 20-day periods at which point the data results

parallel the no vapor barrier wall. The relative humidity levels for the 5-, 10-, 15-, and 20-day

periods are approximately 15%, 5%, 4%, and 3% lower in the Minneapolis placed vapor barrier

wall.

The October test data for the brick wall at monitor position 2 shows a slight increase in relative

humidity for the New Orieans and Minneapolis placed vapor barrier walls in comparison to the no

vapor barrier wall. The increase in relative humidity in the New Orleans and Minneapolis placed

vapor barrier walls is seen at the 10-, 15-, 20-, 25-, and 30-day periods. The increases in relative

humidity are approximately 2%, 4%, 4%, 4%, and 4% higher in the New Orleans and Minneapolis

placed vapor barrier walls compared to the no vapor barrier wall in monitor position 2. The

87

monitor position 3 in the New Orleans positioned vapor barrier wall is identical to the no vapor

barrier wall. The monitor position 3 in the Minneapolis positioned vapor barrier wall shows a

fluctuation in relative humidity levels nearly identical to the levels previously discussed in the April

data section.

The test results for the spruce wall sections, vapor barrier and no vapor barrier, for the month of

January at monitor position 2 shows a slight relative humidity level increase of approximately 2%

at each of the 5 day periods for the vapor barrier located in the New Orleans vapor barrier

placement. The data for monitor position 2 in the Minneapolis placed vapor barrier wall shows a

slight decrease of 2% at each of the 5-day periods. The Minneapolis placed vapor barrier at the

monitor 3 position shovtrs a fiairly significant increase in relative humidity levels when compared to

the no vapor barrier wall system. The relative humidity increase at the 5-, 10-, 15-, 20-, 25-, and

30-day periods is approximately 5%, 10%, 8%, 12%, 10%, and 15%, respectively, which is nearly

identical to the conditions experienced in the brick wall mentioned above.

The April data results for the spruce wall at monitor position 2 remains nearly identical for the

New Orleans and Minneapolis placed vapor barriers as the no vapor barrier models. The monitor

position 3 for the New Orleans placed vapor barrier remains identical to the no vapor barrier

model. The monitor position 3 for the Minneapolis placed vapor barrier shows mixed levels of

increase and decrease starting at the 5-day period. The data shows slight increase in relative

humidity in the vapor barrier model at the 5-day period, and an increase of approximately 5% in

the vapor barrier model at each of the 10- and 15-day periods. The model shows the relative

humidity level rising approximately 5% higher in the no vapor barrier wall compared to the vapor

barrier model at the 20-day period, and this rises to approximately 10% for the 25-day period.

The vapor barrier model's relative humidity level increases approximately 2% more than the no

vapor barrier model.

The July data results for the New Orleans placed vapor barrier wall at monitor position 2 shows a

decrease in the relative humidity levels compared to the no vapor barrier wall beginning at the 10-

day period. The relative humidity levels for the 10-, 15-, 20-, 25-, and 30-day periods are

approximately 2%, 5%, 8%, 10%, and 12% lower in the New Orieans placed vapor barrier wall

compared to the no vapor barrier wall system. The conditions for the Minneapolis placed vapor

barrier wall are approximately 4%, 5%, 7%, 10%, and 13% higher in the vapor barrier wall when

compared to the no vapor barrier wall at the 10-, 15-, 20-, 25-, and 30-day periods, respectively.

The monitor position 3 in the New Orieans placed vapor barrier wall has identical relative humidity

levels when compared to the no vapor barrier wall. The Minneapolis placed vapor barrier wail

shows a decline in relative humidity levels when compared to the no vapor barrier wall at monitor

88

position 3. The relative humidity levels are approximately 8%, 5%, 4%, 3%, 2%, and 2% higher in

the no vapor barrier wall compared to the Minneapolis placed vapor barrier wall.

The October data for the spruce wall at the monitor position 2 remains identical for the New

Orleans vapor barrier position and the no vapor barrier walls. The relative humidity levels for the

10-, 15-, 20-, 25-, and 30-day periods are approximately 2%, 4%, 5%, 5%, and 5% higher in the

Minneapolis placed vapor barrier wall compared to the no vapor bam'er wall system. The monitor

position 3 for the New Orleans placed vapor barrier remains identical to the no vapor barrier

model. The monitor position 3 for the Minneapolis placed vapor barrier shows mixed levels of

increase and decrease starting at the 5-day period. The data shows a slight decrease in relative

humidity in the vapor barrier model at the 5-day period, and an increase of approximately 5% in

the no vapor barrier model at each the 10- and 15-day periods. The model shows the relative

humidity level rising approximately 3% higher in the vapor barrier wall compared to the no vapor

barrier model at the 20-day period. The relative hunrridity level in the no vapor barrier model is

approximately 4% higher for the 25-day period compared to vapor l)arrier model, and the no

vapor barrier model's relative humidity level is approximately 2% higher than the vapor barrier

model at the 30-day period.

Table 3.4, Roanoke summary of relative humidity level data results from WUFI when compared to the no vapor barrier model results

Roanoke

New Orieans VB

placement

Minneapolis VB

placement

Monitor 2 Monitor 3 Monitor 2 Monitor 3

January - Spruce Model 4 — t t4 April - Spruce Model — f July - Spruce Model t — 4 t

October - Spruce Model — — A 4t January - Brick Model — — t 44

April - Brick Model — — t 4t July - Brick Model — — 4 t

October - Brick Model 4 — f 44 ** NOTE: A "A A" means significant increase and a "A^ means mixec 1 increase and decrease.

The actual test run data for the Roanoke wall sections may be found in Appendix 3 at the end of

the report.

89

3.3 Summary The WUFI results that have been discussed only discuss the innpact that vapor diffusion has on

these wall systems and does not consider the effects that air movement has on the same wall

system. The results obtained from the WUFI tests indicate that the effects of vapor diffusion on

the wall system materials as tested are consistent with the recommendations made in the

literature reviewed.

Following the assumption that air moves more moisture vapor than diffusion, the topic of air

carried moisture vapor remains the greatest enemy of the wall system in our residences. The

principle of preventing air-transported moisture has created the need to discuss quality control in

residential construction. The most effective means to prevent or retard the flow of air through a

wall system is to ensure that when the wall is constructed that the air barrier and any penetrations

(such as vents, outlets, etc.) are correctly and carefully detailed and installed to minimize air

movement into the wall system at these locations. It is the opinion of the author that if careful and

thorough attention to these details the effects felt in our wall systems due to moisture vapor

penetration will be lower. The assumption that air moves far more moisture vapor that diffusion

influenced the test data results because the WUFI test data results indicate that diffusion is not

the primary means to be concerned with within our wall systems. The WUFI results indicate that

the dew point was not reached within the wall cavity at the expected dew point locations using the

few dew point calculations that were made in Figures 3.2 - 3.7.

The WUFI tests allowed the following conclusions for the New Orleans wall test runs. The

positioning of the vapor barrier does not affect the manner in which the wall behaves significantly

because the atisorption characteristics of the wall materials do not allow significant quantities of

moisture to diffuse through the wall materials. The effects of air movement and the transport

capabilities through this mechanism are still believed to be the dominant means of vapor

movement, but it remains unproven due to the limitations of the WUFI software program. The

test results for the New Orieans test walls show the necessity of installing a vapor barrier in the

hot, humid climate if diffusion is the only concern. The minor relative humidity decreases seen in

the New Orieans test walls only considering the diffusion through the material would lead to the

conclusion that a vapor barrier is definitely needed in the wall system when air movement is

added to the system.

The conclusions that can be drawn ftôm the Minneapolis data test on the brick and spruce wall

sections are that a vapor barrier should be included in the wall section to handle the effects of

diffusion through the materials in this climate. The literature reviewed stated that the vapor

barrier was needed in this climate and the WUFI test data provide clear validation. The effects of

90

diffusion in this climate would justify inclusion of a vapor barrier in the wall system without even

needing to consider the effects of air movement. The author further believes that if the wall

section could be modeled for air movement through the system, the differences in relative

humidity levels in the no vapor barrier and vapor barrier models would continue to increase, and

the inclusion of a vapor barrier would remain justified in the wall section. It is also still believed

that with the incorporation of air flow the relative humidity level increase on the exterior sections

of the wall would be reduced.

The conclusions that can be drawn from the Roanoke data test runs on the brick and spruce wall

sections show that a brick siding should be selected over spruce siding in a no vapor barrier wall

system. The brick veneer wall would facilitate lower relative humidity levels within the wall cavity

di'e to less vapor diffusion through the material when compared to spruce siding. For the

spruce and brick walls in Roanoke, the recommendation is to not place a vapor barrier in the wall

system because the attained results are similar to the results experienced by placing a vapor

barrier on the exterior side (similar to New Orieans) of the insulation. The placement of the vapor

barrier on the interior side (similar to Minneapolis) of the insulation shows varying changes in the

relative humidity levels on both the interior and exterior wall surfaces. The vapor barrier

placement in this mixed climate location is not recommended. The WUFI program results show

that with the diffusion characteristics in this mixed climate utilizing a spruce and brick wall, it is not

necessary to incorporate a vapor barrier, which is in-line with the literature reviewed.

The effect of air movement remains the primary factor in determining whether or not to utilize a

vapor barrier in the construction of a wall system. The overall lessons learned utilizing the WUFI

sofhware, considering vapor diffusion through the materials within the wall system are:

1. A vapor barrier is necessary in cooling climates to combat the effects of diffusion.

2. A vapor barrier te necessary in heating climates to combat the effects of diffusion.

3. A vapor l)am"er is not necessary in nnixed climates to address diffusion through the wall.

Builders ridicule the literature and construct out of experience rather than what either the

literature or wall analysis calculations reveal. In summary, it is the opinion of the author that vapor

barriers should be used in heating climates at all locations within the structure's foundation, wall,

and roof assemblies. The implementation of a vapor barrier should be included within the

foundation and wall assemblies of all structures in a cooling climate, but the specific application in

the roof remains one area that depends upon the specific, detailed structure design. A vapor

barrier is recommended for the foundation and roof assembly for all structures in the mixed

climate, but the when and where to utilize one within the wall system remains less clear. The

literature states that a vapor barrier is not necessary within the wall in this climate. The principles

91

of flow-through design are to be utilized in this climatic area according to the literature reviewed.

The flow of air through the wall is the primary driving agent of moisture into and out of the wall

assembly depending upon what season the structure is in currently. The principle of flow-through

design allows wetting during one season and drying during the opposite so that moisture within

the cavity attains equilibrium during the course of the year.

92

2-NVB-R-1-AC

100-

■ « y

m^ "\^ / "^ « ̂

10 %- r^^ ii=- , _ - 0

■A.J

^ - —f— —f I» "^^^l*^

-70

1-03

5ân-03 10-Jan-

03 IS-Jan-

03 20-Jan-

03 25-Jan-

03 30-Jan-

03

-♦—Temp outside (°C) 0 0 -1 -5 -3 -10

—•—Relative Humidity - outside

62 SO 70 54 52 80

Oew Point Temp - outside CO

5 4 0 0 0 0

—M—Temp @ monitor position ICC)

10 7 8 5 5 2

—•—Relative Humidity - monitor postion 1

80 80 80 80 82 82

—*-Dew Point Temp - monitor position 1 CO

8 6 6 4 4 1

-Temp outside (°C)

—•— Relative Humidity - outside

Dew Point Temp - outside (°C)

—*f-Temp @ monitor position 1 (°C)

■ Relative Humidity - monitor postion 1

—•— Dew Point Temp - monitor position 1 (°C)

Figure 3.2, Spruce Siding, without vapor barrier, in Roanoice, in January with air conditioning. Outside temperature, relative humidity - outside, Temperature at monitor position 1, and relative humidity - monitor

Dosltlon 1 obtained from WUFI (2003V Dev/ Point data obtained from Stein B. and Reynolds. J. ri992V

2-NVB-R-4-AC

100

90

80

70

60

50

40

30

20

10 ^ -H,,.^ In "Ki "n"^**'*!^^ I

5-Apr-03 1&-Apf-03 15-Apr-03 20-Apr-03 25-Apr-03 30-Apr-03

-Temp outside (°C) -Relative Humidity - outside


-Temp @ monitor posifion 1 -CO -Relative Humidity - monitor

postion 1 -Dew Point Temp - monitor

position 1 (°C)

5-Apr-03 10 52

14

80

12

10-Apr-03 8

37

11

80

10

15-Apr-03 10 82

10

82

20-Apr-03 15 62 11

15

82

13

25-Apr-03 16 62 12

19

80

17

30-Apr-03 10 90

13

78

-Temp outside (°C)

-Relative Humidity - outside


-Temp @ monitor position ICO

-Relative Humidity - monitor postion 1

-Dew Point Temp - monitor position 1 (°C)

Figure 3.3, Spruce Siding, without vapor barrier, in Roanoice, in April with air conditioning. Outade temperature, relative humidity - outside. Temperature at monitor position 1, and relative humidity - monitor

position 1 obtained from WUFI (2003). Dew Point data obtained from Stein B. and Reynolds, J. (1992).

93

2-NVB-R-7-AC

0 5-JUI-03 lO-Jul-03 15-Jul-03 20-Jul-03 25-Jul-03 30-]ul-(

-Temp outside (°C) -Relative Humidity - outside


-Temp @ monitor position 1 (°C)



5-Jul-03 lO-Jul-03 15-Jul-03 20-Jul-03 25-:ul-03 30-Jul-03 25 64 20

25

77

23

23 60 18

23

74

20

27 55 21

27

72

23

25 82 23

25

70

21

22 52 16

23

67

19

22 82 20

25

67

21

-Temp outside (°C)






Figure 3.4, Spruce Siding, without vapor barrier, in Roanoke, in July with air conditioning. Outside temperature, relative humidity - outside, Temperature at monitor position 1, and relative tiumidity -

monitor position 1 otrtained from WUFI (2003). Dew Point data otrtained from Stein B. and Reynolds, J. (1992).

2-NVB-R-lO-AC

100

90

80

70

60

50

40

30

20

10

«.,

, / N y N ■ m «

\, ^^ "\^ N ^ ^B

8- -= **-5iS=: % \

-Temp outside (°C)



-Temp @ monitor position 1 ("C)

- Relative Humidity - monitor postion 1

- Dew Point Temp - monitor position 1 ("C)

5-CX±-03 lO-Oct-03 15-Oct-03 20-Oct-03 25-Oct-03 30-Oct-03

5-Oct-03 lO-Od- 03

15-Oct- 03

20-Oct- 03

25-Oct- 03

30-Oct- 03

—•—Temp outside ("C) 19 16 16 8 12 10

-•— Relative Humidity - outside 70 92 75 55 70 54


16 15 14 5 9 6

—X—Temp @ monitor position 1 CO

17 18 17 13 16 16

—■—Relative Humidity - monitor postion 1

81 80 79 77 77 77


15 16 15 11 14 14

Figure 3.5, Spruce Siding, without vapor t>arrier, in Roanolce, in October with air conditioning. Outside temperature, relative humidity - outside, Temperature at monitor position 1, and relative humidity -

monitor position 1 obtained from WUFI (2003). Dev/ Point data oljtained from Stein B. and Reynolds, J. (1992).

94

2-VB-M-l-AC

100 -

\

60 - \ \ "*

0 5-3 in*83 10-Ji>h"e3—15.- ip'^^SlO- jrtD3—BS* ^h^3 ~^-. ar

V *

SOan-03 10-]an- 03

15-]an- 03

20-]an- 03

2S-:an- 03

30-]an- 03

♦ Temp outside (°C) -4 -20 -18 -10 -6 -25

-•—Relabve Humidity - outside 90 55 60 72 80 55

Dew Point Temp - outside 0 0 0 0 0 0

—K—Temp @ monitor position 1 4 -6 -10 2 2 -10

—•—Relative Humidity - monitor posdon 1

80 80 80 80 80 80

—•—Dew Point Temp - monitor position 1 (°C)

3 0 0 1 1 0

-Temp outside (°C)

-Rdative Humidity - outside

Dew Point Temp - outside ("C)


-Rdative Humidity - monitor postion 1


Figure 3.6, Spruce Siding, with vapor barrier, in Minneapolis, in January with air conditioning. Outside temperature, relative humidity - outside, Temperature at monitor position 1, and relative ttumidity - monitor

position 1 obtained from WUFI (2003). Dew Point data obitained from Stein B. and Reynolds, J. (1992).

100-

90 -

80 -

70

60

50

40

30

20

10

2-VB-NO-7-AC

——~_ —•—Temp outside (°C)

-■-Relative Humidity - outside Dew Point Temp - outside (°C)

-K-Temp @ monitor position 1 (°C)

-i»-Relative Humidity - monitor postion 1


n m ^.____^ _——

"^~'~~~^^-^ ~~^~~^-«

O—"^^^-K

5-J ul-03 lO-Jul-03 15-JUI-03 20-JUI-03 25-Jui-03 30-Ju -03

5-JUI-03 IO-Jul-03 15JUI-03 20-JuH)3 25-Jui-03 3(Klul-03

-•-Temp outside (°C) 25 28 28 28 28 25 -■-Relative Humidity - outside 84 84 80 84 84 80

Dew Point Temp - outside ("C) 23 26 25 26 26 23 —*fr—Temp ft monitor position 1 (°C) 25 25 25 25 28 25 -■—Relative Humidity - monitor

postion 1 77 72 70 65 60 55

-•—Dew Point Temp - monitor position 1 (°C)

22 21 21 20 22 19

Figure 3.7, Spruce Siding, with vapor t>arrier, in New Orleans, in July with air conditioning. Outside temperature, relative humidity - outside. Temperature at monitor position 1, and relative humidity - monitor

position 1 ot>tained from WUFI (2003). Dew Point data obtained from Stein B. and Reynolds, J. (1992).

95

3.4 References Cited stein B. and Reynolds, J. (1992). Mechanical and Electrical Equipment for Buildings: 8th

Edition. John Wiley and Sons, Inc.; New York; 1627 p.

WUFI. (2003). WUFI: Warme-und Feuchteransport instationar (Transient Heat and Moisture Transport), Educational Soâre Program. Oak Ridge National Laboratory; Oak Ridge TN; obtained from www.ornl.aov/ORNL/BTC/moisture/. accessed on 1 Sep 03.

96

4.0 Summary and Conclusions

97

4.1 Summary Moisture dissipation from witliin a wall is directly related to both the air movement and vapor

diffusion through the structure's wall assembly materials (Carll, 2000). The rampant use of vapor

barriers in residential construction has in many instances created redundant vapor barriers within

the wall cavities that trap moisture and water. Even if the vapor barriers are not redundant, the

vapor barrier's placement is oftentimes in the wrong location, creating as many problems as

redundancy. A vapor barrier's location should be carefully designed and specifically applied in

relation to the wall design, climatic conditions, and directional orientation (North, South, East, or

West) of the wall. In order to control moisture, designers and builders must look holistically at the

indoor and outdoor atmospheric conditions of the building system's design to create the

appropriate foundation, walls, and roof sections for the building assembly (Caril, 2000). The

recommended placement of a vapor barrier should not be universal even within similar climatic

regions. The specific, individual wall system design and climatic conditions should be studied

and incorporated when detemiining whether or not to use a vapor banier.

The major problem cited by independent residential builders in new housing construction is

moisture, primarily rot, decay, and the growth of molds and fungi. Condensation and moisture

related problenns were first recognized and investigated in a 1923 Forest Products Laboratory

survey of dwellings due to early exterior paint failure on residential houses (U.S. Forest Service,

1949). It has more recently been reported, "with the exception of structural errors, 90% of

building construction problems are associated with water" and the harmful effects related to its

penetration into our structures (Trechsel, Achenbach, and Launey, 1982). Current building codes

and property standards also contribute to this problem because the methods being employed are

prescriptive rather than performance oriented and these codes have tried to create a universal

approach for construction rather than looking holistically at the wall assembly components

(Trechsel, Achenbach, and Launey, 1982 and Shenwood and Moody, 1989).

The recommendations that follow may or may not be in line with the requirements made under

the codes and property standards currently in use. The recommendations are broken down into

common areas of interest within our structures, foundation, walls, and roofs. Each section is a

summary of what the report states in more detail.

4.2 Detail Conclusions and Specifics for Foundations, Walls, and Roofs 4.2.1 Foundations

The foundation vapor barrier design is straightforward and consistent for heating, cooling, and

mixed climates. A vapor barrier should be included in all climates as a ground cover under slab-

on-grade and in crawl spaces. The accumulation of moisture through the foundation/support

elements (slab, basement, crawl space, etc.) is the primary point of entry into residential

98

construction assennblies (Suprenant, 1994). The incorporation of vapor barriers in the foundation

design is only going to be as effective as the drainage mechanisms facilitate. Designing proper

drainage includes not only collecting the water, but also effectively moving the water out and

away from the structure so that the water does not accumulate and then migrate back up and into

the wall system. Two typical design details for the slab-on-grade and a crawl space may be

seen in Figures 4.1 and 4.2.

The placement of the sub-slab vapor barrier will perform a dual role in the structure's moisture


structure's assembly (Lstiburek and Carmody, 1991). The sub-slab vapor barrier's role is to break

capillarity, and it provides the building with its first preventative measure in dealing with moisture

and minimizing the potentially harmful effects within the structure. Special care should be taken

to ensure that the vapor barrier's integrity is maintained since it is also fulfilling the role of an air

barrier.

j. F«ttfi*!«ts3 wwiJ Pipe

Figure 4.1, Adapted standard slab-on-grade and basement detail from Ramsey and Sleeper (1992).




joints should be lapped at least six inches, and the vapor barrier material should be as impervious

as possible to any breaks, punctures, or other such penetrations (Suprenant, 1994). The role of

the vapor barrier in this particular application should be designed and constructed in a similar

manner as an air barrier within the wall system. The vapor barrier should be placed on top of,

and in direct contact with, the compacted subgrade material. Then, on top of the vapor barrier

and below the concrete slab, a three-inch thick layer of sand or varied sizes of gravel should be

99

applied and lightly compacted ûprenant, 1994). Gravel is recommended over sand t)ecause

gravel is less easily displaced during ttie placement of the concrete slab and provides a

consistently more uniform surface for the slab's placement (Suprenant, 1994). A discussion with

a residential house builder stated that this layer is seldom incorporated because of the significant

cost and the perceived benefits of incorporation do not outweigh the increased cost of installation

(Vinson, 2003). Spedal care and oversight should be taken during the concrete placement phase

since the vapor barrier's effectiveness is proportional to the integrity of the barrier membrane

below (JLC Staff, 1993).

•Vgegr^*^

0-t)fawN»«se PiFc^

^pITl't Figure 4.2, Adapted standard crawl-space detail from FPL (1949) and Ramsey and Sleeper

The requirements, as outlined in the CABO and ICC codes, make recommendations for the

incorporation of vapor barriers in the on-grade, sub-slab section that are in line and follow the

recommendations and guidance discovered during the review of literature.

4.2.2 Walls

The climate where the residence wall is to be located, in conjunction with the composition of the

wall components, strictly define how, where, and if a vapor barrier should be included in the

design. As previously discussed, the directional orientation of the wall system also plays a

significant role in determining when to place a vapor barrier within the wall system. The internal

100

wall temperatures vary significantly depending on if the wall is exposed to climatic conditions on

the north, south, east or west sides of the structure. The wall assembly temperatures and

thermal mass effects are greatly impacted by the directional orientation. The examples selected

do not represent all known housing solutions, merely the most popularly used solutions in the

residential construction industry today. The wall system assembly descriptions with the

associated component R-values and material thicknesses used in this paper's investigation may

be found in Table 4.1.

Table 4.1 -Wall system components, R-value, and materials thicknesses Wall System Model & Components R-value Material Thickness

Wood ?iang fno0el: - Outside air .17 in winter & .25 in summer N/A - WDod siding, beveled, lapped (back primed) .81 .5" - Furring strips or similar air gap 1.35 .25" - Building paper/ housewrap, permeable .06 Negligible -1/2" Douglas fir plywood .62 .5 - Unfaced rolled batt-insulation 11 3.5" - Gypsum board with paint .56 5/8" - Inside air .68 N/A

BrioH ven^^r model (HgM wood frm^): - Outside air .17 in winter & .25 in summer N/A - Face bricl< .2 2.66" -Airspace 1.35 .25" - Building paper/ housewrap, permeable .06 Negligible -1/2" Douglas fir plywood .62 .5" - Unfaced rolled batt-insulation 11 3.5" - Gypsum board with paint .56 5/8" - Inside air .68 N/A

Plaster veneer model (on fight wood frame): - Outside air .17 in winter & .25 in summer N/A -Stucco .1 .5" - Durarol(® .26 .5' - Building paper/ housewrap, permeable .06 Negligible -1/2" Douglas fir plywood .62 .5" - Unfaced rolled batt-insulation 11 3.5" - Gypsum board with paint .56 5/8" - Inside air .68 N/A

Concrete shell/Holistic house model: - Outside air .17 in winter & .25 in summer N/A - Sealed concrete .95 2' - Styropor insulation 38.25 8.5" - Gypsum board with primer coat and latex paint .56 5/8" - Inside air .68 N/A ***AII R-valueswere obtained from Stein and Reynolds (1992), pages 136-14; 1, with the exceptions of Styropor and Durarok® that were obtained from manufacturer's specifications.

The conclusions developed regarding where to install a vapor barrier in a cooling climate and a

heating climate are in line with the information discovered during the literature review. The WUFI

program results indicate the same conclusions as those discovered during the literature review.

The vapor barrier should be installed on the warm-in-winter side of the insulation for both

climates' wall system design solutions (heating climate: the vapor barrier is placed on the interior

face of the insulation; and the cooling climate: the vapor barrier should be placed on the exterior

face of the insulation). The positioning of the vapor barriers within the brick veneer and spruce

siding model wall cavities for both heating and cooling climates are diagrammed in Figure 4.3.

101

The positioning of the vapor barrier in these locations follows the literature reviewed, and

matches the vapor diffusion results obtained from the WUFI Student Version software-modeling

program.

The potential for redundancy still exists in these structures. The effects of the redundancy

(caused by multiple layers of latex paint) in a cooling climate's structure are expected to be worse

than those in the heating climate. The placement of the intentional vapor barrier on the exterior

side of the insulation in a cooling climate and the inclusion of the inadvertent vapor barrier on the

interior side of the gypsum board will create a potential vapor trap in the insulation and gypsum

board components of the cooling climate's wall assembly. The effect of redundancy caused by

paint in the heating climate creates a vapor trap inside of the gypsum board, so it may be

concluded that the effects of vapor accumulation will be significantly minimized.

i I ,1 mum

"jV

mdkm

M

.V

T

Monitor positions in program

50 mm air layer

Brick/Spruce

■5mm air layer

60 minute building paper

-Exterior grade plywood

-Fiber glass

Gypsum wallboard

0 mm air layer

New Orleans Minneapolis V.B. V.B.

5 mm polyethylene vapor barrier position

Figure 4.3 - Typical Brici( Veneer and Spruce Siding wall section composition and the associated vapor barrier location within each section, drawing by author

In a mild, more temperate climate a vapor barrier is not necessary. For example, for the bricl<

veneer wall it is recommended that no vapor barrier be included because the vapor diffusion

difference varies only slightly when compared to the same wall with a vapor barrier. A vapor

102

barrier may be utilized, in the same location as that in a cooling climate, but the added expense of

a vapor barrier should dictate its exclusion since no reductions in relative humidity were observed

in the WUFI data results for vapor diffusion. Proper ventilation and clear weep holes in this wall

cavity and climate must exist because once water enters the cavity it should have both a means

to exit and a means to dry. If the water is not allowed to exit once it enters the cavity, the water

will seek equilibrium within the space and migrate across other materials. The spruce siding wall

assembly has the same recommendations as those for the brick veneer wall. A plaster veneer

wall should be avoided in this climate. The plaster wall system's component composition

(Durarok® and plywood) on the interior of the plaster coat behaves like a vapor retarder for vapor

diffusion through the wall system. It is recommended that this assembly be avoided in mixed and

heating climates. A concrete shell model that contains a super insulated wall should not

necessitate a vapor barrier.

4.2.3 Roofe

The use of a vapor barrier in the roof/ceiling components of the assembly is effective and

recommended as a means of being able to reduce the ventilation requirements in this part of the





making a determination for when to utilize a vapor barrier. Table 4.2 was developed to help

explain the roof design recommendations contained in this report.

Table 4.2, Various Roofing V.B. Applications According to Ciimate

Roof Type Heating Climate Mixed Climate Cocking Climate Flat Roof - V.B. may be installed

between deck and insulation, If design calculations prove its necessity

- V.B. should be installed between deck and insulation, if the winter temps are as discussed in codes and design calculations necessitate incorporation

- V.B. not needed

Roof with Attic

- Super low permeance plastic sheet V.B. &air bam'er designed between built-up roofing and insulation in 8000+ heating degree day climates - Higher penneance V.B. &

built-up roofing and insulation - Circulation/venting must be provided - Design calculations must be utilized to detemiine inclusion or exclusion

- Higher permeance V.B. & air barrier designed between built-up roofing and insulation - Circulation/venting must be provided - Design calculations must be utilized to determine inclusion or exclusion

- V.B. should not be used in this climate - Air drculation/venting sufficient in hot, dry environments - Air drculation/venting should be avoided due to high moisture concentrations in hot, humid environments - Air barrier designed to prevent air leakage

103

Roof Type Heating Climate Mixed Climate Cooling Climate Cathedral Ceiling



- V.B. not necessary - Ventilation requirements same as attic space and should occur at eave and ridge if ventilated

Note: The CABO and ICC codes state, '[n]et free cross-ventilation area may be reduced to 1 to 300 with installation of vapor retarder (nrjaterial with a transmission rate not exceedng 1 perm) installed on the warm side of ceiling."



system. The only fimi conclusion with regards to the inclusion or exclusion of vapor barriers in

the roof design is to calculate the specific point where the dew point is reached vwthin the roof

system and place the vapor barrier on the next cold surface. The influence of air movement must

be considered, as well as the potential for drying through air movement to the interior or exterior

of the roofing system materials. The designer must also be cognizant of the fact that if a vapor

barrier is included and the roof develops a leak, the vapor barrier could behave as a vapor trap

and cause the system to retain the water by not allowing it to escape.

The codes state that the "[n]et fl-ee cross-ventilation area may be reduced to 1 to 300 with

installation of vapor barrier (material with a transmission rate not exceeding 1 perm) installed on

the warm side of ceiling" (CABO, 1995 and ICC, 2000). The allowed reduction does not appear

to make any sense for the climatic areas where roof ventilation is required. One of the purposes

of roof ventilation is to allow the space to dry out should the space below the roof become wet.

The ventilation reduction allowance under the codes would hamper drying through ventilation.

The opinion of the author is that the codes allowed reduction in ventilation within the roof cavity is

not recommended. The ventilation of the roof is necessary in effectively combating moisture

accumulation in heating and mixed climates but not in cooling climates.

4.3 Summary of Lessons Learned The following points are the most important and salient points discovered in the course of the

literature reviewed in conjunction vinth the WUFI test results:

1. In a cokJ climate, a vapor barrier should be installed close to the interior (warm) side of

the insulation.

2. In a hot, humid, tropical climate a vapor banier should be placed on exterior (warm) side

of the insulation.

3. In mild, more temperate climates a vapor barrier may or may not be necessary

depending upon the specific wall materials. For example,

104

a. The brick veneer wall may or may not require a vapor barrier installed on the

exterior side of the insulation. It is recommended that no vapor barrier be

included because the vapor diffusion difference (with a vapor barrier placed on

the exterior side of the insulation) is not too different when compared to the same

wall without a vapor banier. The added expense of a vapor barrier should dictate

not including one in this design since no significant benefits were observed in the

WUFI test data results. The incorporation of proper ventilation and weep holes in

this wall cavity design is a necessity because once water penetrates the cavity it

should have a means to exit and a means to dry.

b. A spruce siding wall has the same recommendations as those made with the

brick veneer wall previously discussed.

c. A plaster veneer wall should be avoided in this climate. This exterior wall

system's components (Durarok® and plywood) behave like a vapor retarder for

diffusion through the wall system and as such shouki be avoided.

d. A concrete shell that is super insulated does not necessitate a vapor barrier.

4. A vapor barrier should only be used if needed, and the use should be based upon the

specific wall system design, clinnate and orientation (North, South, East, or West) of the

structure's location and specific wall design. The climatic differences experienced by the

different directional orientations may dictate different applications of vapor barriers within

the same structure, but the specifics should be calculated for each structure.

5. A vapor barrier in a basement shouki be implemented in the same manner and location

as it was (was not) in the at)ove-grade wall system.

6. A vapor barrier performs as a ground cover below the slat)-on-grade and in crawl spaces.

The vapor barrier's inclusion in these locations helps reduce moisture transport through

capillary movement/suction from the soil up and into the structure's materials.

7. The vapor barrier does not have to be airtight, but should be installed with as few

imperfections as possible to prevent the flow of air and vapor into the envelope. A rule of

thumb when installing vapor barriers is "a vapor barrier that covers 90% of the surface is

90% effective" (JLC Staff, 1993).

8. Common wall cover applications act as vapor barriers p.e., multiple layers of non-vapor

retarding paint (latex), 3+ coats; and wallpaper (especially vinyl wall covering)].

9. Air moves far more moisture than diffusion through materials.

10. The building's wall cavity shoukJ not be ventilated in hot, humid (cooling) climates.

11. The building's wall cavity shouM be ventilated in temperate and coki (heating) climates.


13. Care should be taken when installing an air barrier because the air barrier is only as

fiindional as the air barrier's material integrity (i.e., be fl-ee of cuts, tears, punctures, rips).

105



15. All walls are different and will behave differently depending upon climate, orientation, and

how they are to be constructed.

The overall lessons learned utilizing the WUFI software considering only vapor diffusion through

the materials within the wall system are:

1. A vapor barrier [s necessary in cooling climates to combat the effects of vapor diffusion.

2. A vapor barrier is necessary in heating climates to combat the effects of vapor diffusion.

3. A vapor barrier is not necessary in mixed climates to address vapor diffusion through the

wall system.

The effects of air transported vapor remains the primary factor in determining whether or not to

utilize a vapor barrier in the construction of a wall system. The WUFI results show that the effects

of vapor diffusion are in line writh those recommendations discovered during the literature review.

The effects of air movement within the cavity and across the materials remains unproven due to

the limitations of the WUFI software.

The effect of air movement through the building materials remains the primary issue to be

addressed in the building system design and construction. The design of the detail is a

straightforward process that can be obtained from standard detail sources. How the detail is

constructed should be the primary area of concern during construction. The air barrier should be

installed with no penetrations, cuts, tears, and openings. The air barrier's integrity is critical if the

wall components are to be kept dry and not subjected to the harmful effects associated with

moisture penetration due to air movement. The air barrier's integrity should be checked prior to

the subsequent building assembly layers installation. The vapor barrier's integrity, on the other

hand, does not have to be as perfect if the air barrier has been installed correctly. If the vapor

barrier only has to combat the effects of vapor diffusion through the materials, rather than the

effects of air movement, then a vapor barrier with a few minor blemishes will perform its role

correctly and efficiently. If the vapor barrier is to fulfill the dual role of vapor and air barrier then

the rules for installing an air barrier apply.

The quality assurance and quality control process is critical during the construction of the air

barrier and the sub-slab/ground cover vapor barrier installation. These barriers should be

installed as imperviously as possible and their integrity should be carefully checked prior to

subsequent work being placed on top of their respective surfaces. The effectiveness of the wall

system air barriers and the sub-slab/ground cover vapor barriers are only as effective as they are

continuous (JLC Staff Report, 1993). Any and all penetrations should be patched or sealed. The

106

CWQC procedures during construction of these barriers are vital to tlie success of the wall

assembly in the building as it combats moisture.

The directional orientation that the wall faces plays a significant role in the determination of

whether or not to include a vapor barrier within the wall. The directional orientation of south and

west facing structure walls will require different design parameters than walls facing the north and

the east. The south and west facing walls face more effects from thermal mass and heat gain

due to their particular directional orientation. These walls can be expected to maintain higher

temperature readings than those on the north and east facing walls throughout the year and the

dew point temperatures, and possibly the dew point location, within the wall may vary significantly

compared to the same wall on the east and north faces of the structure.

Vapor barriers, listed in Table 4.3, are often times used redundantly or inadvertently because of

the many potential materials that fulfill the vapor barrier role. Vapor barriers on new construction

are often times an intentionally installed material. As a building is renovated and repaired,

redundancy and inadvertent vapor bam'ers are often tinries created.

Table 4.3 - Vapor barrier definition and examples DeHniOon ExamfilBS

A Vapor Barrier or Vapor - Polyethylene sheet membrane (Visquene) or film (varying thteknesses, 2-6 millimeters Diffusion Retarder lias and in 3-20 foot roHs) sealed with manufocturer recommended caulk, sealants, and tapes been defined as a -EPDM material to: - Plastk: sheeting 1.) "The control of water - Rubber memtxanes vapor diffusion to reduce -Glass the occurrence or - Aluminum foil intensity of - Sheet metal condensation" (Straube, - Oil-t)ased paint 2001) that is driven by - Bitumen or wax impregnated kratt paper diffusion, - Wall coverings and adhesives 2.) A vapor barrier may - Foil-feced insulating and non-insulating sheathings have imperfections and - Vapor retarder latex paint small cracks in its - 2 coats of acrylk: latex paint top coating with premium latex primer surface vnlhout greatly - 3 coats of latex paint impairing the - Scrim (open-weave fabric like fiberglass fabric) performance of the - Hot, asphaltic mbberized membranes permeable vapor barrier - Some insulatk>ns (elastomeric foam, cellular glass, foil faced isofoam) if sealed (Straube, 2001), or - Aluminum or paper faced fiberglass roll insulatnn 3.) As defined by - Foil backed wall board building codes as - Rigid insulation or foam-board insulation anything with a -1/4 inch Douglas fir plywood with exterior glue permeability of 1 perm or - High-performance cross-laminated polyethylene less (Lstiburek, 2000) (Infonnatnn from Lstiburek, 2000; ICAA, 2002; Spence, 1998; Bordenaro, 1991; Maness,

1991; Lotz, 1998; Lstiburek and Cannody, 1991; Forest Products Lab, 1949; DoE, 2002)

For example, a common manner in which an inadvertent vapor barrier is created in a residence is

when the occupants repaint a room. The structure's wall, when constructed, may have had a

primer coat on the gypsum wallboard and then two coats of non-vapor retarding latex paint.

When the occupants repaint their walls to up-date their home with two new of coats of latex paint,

they have unintentionally created a vapor barrier on the interior side of the wall. The inclusion of

107

this vapor barrier either creates a vapor barrier where none previously existed or has now^ created

a redundant vapor barrier because of one that was intentionally installed during construction.

Unintentional vapor barriers are frequently incorporated into buildings and should be avoided

when possible. Caution should be taken when renovating or updating residences/structures.

In conclusion, builders ridicule the literature and construct out of experience and not what either

the literature or wall analysis calculations reveal. The different clinnate summaries and opinions of

the author are as follows:

1. Heating Climate: Vapor barriers should be used in heating climates at all locations within

the structure's foundation, wall, and roof assemblies.

2. Cooling Climate: The implementation of a vapor barrier should be included within the

foundation and wall assemblies of all structures in a cooling climate, but the specific

application in the roof remains one area that depends upon the specific, detailed

structure design.

3. Mixed Climate: A vapor barrier is recommended for the foundation and roof assembly for

all structures in the mixed climate, but the when and where to utilize one within the wall

system remains less clear. The literature states that a vapor barrier is not necessary

within the wall in this climate. The principles of flow-through design are to be utilized in

this climatic area according to the literature reviewed. The flow of air through the wall is

the primary driving agent of moisture into and out of the wall assembly depending upon

what season the structure is in currently. The principle of flow-through design should be

adhered to since it allows wetting during one season and drying during the opposite so

that moisture within the cavity attains equilibrium across the wall section during the

course of the year.

108

4.4 References Cited Bordenaro, M. (1991). "Vapor Retarders Put Damper on Wet Insulation." Building Design and

Constnjction. 32(9), 74-77.

Carll, C. (2000). "Rainwater Intrusion in Light-Frame Building Walls." From Proceedings of the 2nd Annual Conference on Durability and Disaster Mitigation in Wood-Frame Housing: November 6-8,2000, Madison Wl, from www.toolbase.ora. accessed 3 Jun 03.

Council of American Building Officials. (1995). CABO: One and Two Family Dwellinc Code. 1995 Edition. Fourth Printing. CABO; Falls Church VA; 350 p.

Department of Energy. (2002). "Vapor Difllision Retarders and Air Barriers." Consumer Energy Information: EREC Reference Briefs obtained from www.eere.enerav.qov/consumerinfo/rfbriefe/bd4.html. accessed on 28 May 03.

Insulation Contractors Association of America (ICAA). (2002). "Technical Bulletin: Use of Vapor Retarders." ICAP; Alexandria VA. Obtained from www.toolbase.ora. accessed 3 Jun 03.

International Code Council. (2000). International Residential Code: For One and Two Family Dwellings. International Code Council; Falls Church VA; 566 p.

JLC Staff Report. (1993). "The Last Word (We Hope) on Vapor Barriers: Answers to the most common questions about moisture migration through walls and ceilings." Journal ofLi^t Consfn/cffon, 11(11), 13-17.

Lotz, W. (1998). "Specifying Vapor Barriers." Building Design and Constnlction,Z9(^^),50-5Z.


Lstiburek, J. ^000). Builder's Guide to Mixed Climates: Details for Desian and Construction. The Tauton Press; Newton CT; 328 p.

Lstiburek, J. and Carmody, J. (1994). "Moisture Control for New Residential Construction" in Moisture Control in BuikJinas. ASTM Manual Series: MNL 18; Philadelphia, PA; 321-347.

Lstiburek, J. and Camnody, J. (1991). Moisture Control Handbook: New, low rise residential construction. Oak Ridge National Laboratory; Oak Ridge TN; 247 p.

Maness, G. (1991). 'Preventing Wall Deterioration." Journal of Property Management. 56(5), 33-38.

Ramsey, C and Sleeper, H. (1992). Construction Details from Ardiitectural GraMc Standards. Eight Edition. ecSted by James Ambrose. New York, John Wiley & Sons, Inc.

Spence, W. (1998). Construction Materials. Methods, and Techniques. Delmar Publications; NewYork;1195p.

Suprenant, B. (1994). "Sub-Slab Vapor Baniers." Journal of Light ConstrucSon,M{B), 37-39.

U.S. Forest Service. (1949). Condensation Control: in dwelling construction by Forest Products Latxiratory, Forest Senîce, U.S. Department of Agriculture in collaboration with the Housing and Home Finance Agency, Forest Products Laboratory; Madison Wl; 73 p.

109

Vinson, J. (2003). Telephone interview with Joe Vinson of Joe Vinson Builders (IVIobile, Alabama) on 21 Aug 03.

WUFI. (2003). WUFI: Warme-und Feuchteransport Instationar (Transient Heat and Moisture Transport), Educational Software Program. Oak Ridge National Laboratory; Oak Ridge TN; obtained from www.ornl.qov/ORNL/BTC/moisture/. and accessed on 1 Sep 03.

110

Appendix 1 - New Orleans Test Data

111

30

O

e 3 «^ 2 o OL E

"~" MonSwpos. 1 (Exterior Surface) "^-Monitorpos. 2

E a X $

10 15 20

Time [d]

Pralort: Prcjtrrt ard Report / Case 1,ficcVVonnerr,laitc!- 1.N'*'EHO.i-AC

112

30

r-, 20 O

3

O. E

10

£ 3 I

i5 o Of

-10

100

75

50

25

' MonRorpDS. 3 ■ MonRorpos. 4 (InlBrinr Surface)

—— MotlHc "-"-MonSc

>rpDS. 3 itpos. A (Inte 'ior Sufface)

^ ::ixO ie^^^^t>

^^

\-J

10 15 20

Time [d]

25 30

Prclcrt- Prclort and RcpnH /Case 1: Bf ck VnncorModel - l-NS'E NO-I-AC

113

30

O

&

E o a. E

-" MonKorpos. 1 {Exterior Surface) •-MonHorpos. 2

100

1 X S -«>

•— MoniSoTpos. 1 (Exterior Surface) —-MonBorpras. 2

14.4 19.2

Time [d]

28.8

PrcjDrt: Prc^Drt ard Report i" Case 1: Bf ck Vcnepr Hntlfi! - 1-K'*'E N0-4-AC

114

30

^ 20 p

e

m a. £

JO

■D E 3 X ?

10

-10

100

75

50

25

—" MonPforpos. 3 — Moni?(Mp.DS. A {IntBrior Surface)

1 ■~~" Monitc ^-MonSc

1

jrpos. 3 jrpos, 4 (IntB ior Sutfacs)

1

^ rd^

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

PrcjD* PfcjniS and Report/Case 1:firckVflncfirMflria!- 1-NVE-NO-4-AC-

115

60

^ 40 O

& 3 E O. £ |2

E I

i5

20

— MonRc — MonSc

ktpos. 1 (Extc vTpos. 2

rior Surface)

i^^KîmmPP^**t^^0*A

Pre)!!* Projoa and Ropoit f Cjio 1: B«V VcncorMoacl • l-NOT NO 7JIC

116

30

O p

& 3 *^ E Q. E

E 3 X I JO

"~~ MonRorpos. 3 —"-Monilorpos. 4 (Interior Sutface)

20 r^

10

10 15 20

Time [d]

PrcJDft Prcjo!! anil Rcpcrt / CasR 1: Bj-^rk VdncBr ModGl - 1-NVE NO-7^C

117

30 1 i I ' Monitorpos. 1 (Exterior Surface) • MonP.orpos. 2

o B 3 c Q. £

is E X

o

-10

100

75

50

25

i — Monitc -"MonRc

^—^ tt^—

irpos. 1 rpos. 2

(Ext

1 T 1 =rior Surface)

IP i

w i^ k i » r i/ii 1

10 15

Time [d]

20 25 30

Prcject PrcjnrtardRflpnrtfCasD liBrc*. VsinnDrMotfoi- l-NV'B-NO-tO AC

118

o o

E

30 ■—• MonSoTpos. 3 "—- Monilorpos. 4 (Interior SuTfacs)

20 P^

10

-10

SIMIPU

T3 1

100

75

50

25

—— MonRc — Monitc

i tfpas. 3 ►rpos. 4 (Inte

1

ior Surface)

V,

10 15 20

Time [d]

25 30

Prcjctt PtcjBCt BjTd Report iCase 1: Erck VeneerMndo! - t-NVS NO-f 0-AC

119

o

3 E « o. E

E X S

Prcjisa- Prcjoa iwa Rspnrt I Case 1: Ercl Vcnccr Modo! - l-VE MO-1 -AC

120

30

O a

& 3 &

E |2

10

■D E 3 X

-43 TO a>

DC

-10

100

75

50

25

—~ MonRorpos. 3 —- MonRorpos. 4 {IntErior Surface)

1

—— MonRo —"MonRo

►rp-as. 3 trpos. 4 (IntH •ior Surface)

^ :C:x:^ ̂ -^ ^^^m-t

X—

0 5 10 15 20

Time [d]

25 30

PrcJ&cl; Prcjita and Report / CasiD 1: BTck Vflnner Wade! - i-V&NO-l AC

121

p ■niiniiJ

&

E a. E .©

100

is E 3 I $ «

on

• MonRwpos. 1 (Exterior Surface) • MonRorpos. 2

14.4 19.2

Time [d]

28.8

Prcinrt Presort ard Report {Cas.fi 1: BrrX Wttnovr h !t-1-VE-MO-«-AC

122

o

e a. E

30

20

10

-10

—— MoniSc ■—Monftt

ytpos. 3 >r[>3s. 4 (Inte 'ior Sufface)

E 3 X S IB i5

14.4 19.2

Time [d]

28.8

PrejDflt PrcjBCt and Rcpnrt i* Case 1: Brcit Vfineisr Madft! - 1-NVE NO-4-*C

123

o a

£

o Q. E |2

60

40

20

"~~ MoniSc —— MoniSc

1 rpos. 1 {Exte trpos. 2

1 rior Surface)

.

m^Kai^tmm*t^m0** »

£ 3 I

10 15 20

Time [d]

Prcârt Prciod! afvil Report rCum 1: Brck. Vfinocr Wodc! - l-VB-NO-T-AG

124

30

O 0

& 3

S <D Q. E

10

-10

«— MonKc ^-MonKc

1 rpos. 3 ^rpos. 4 (Inte

r ■

'inr Surface)

E 3 X

10 15 20

Time [d]

Prajcil: Piojort ara) Ropoit I Cast 1: B/c* Vcnoor UaHitl • 1-V& NO-T-AC

125

30

^ 20 O

3

&

E |2

10

-10

100

£ 75

2- •D 1 3 X 50

5 TO

25

—^ 1

•— Monflorpos. 1 (Ext ^-MonRorpos. 2

^Wfil i 1 f

1

=riar Surface)

M H " yi "i r

25 30

Prcjfttt PtcjBrt ard Report i* Case t: ficcV Vonocr Mode! - 1-VE-MO-10 AC

126

30

O a

e 1 O a. E |2

10

E 3 X $

-10

100

75

50

25

■

-—MonKc — Montic

>rpos. 3 apos. 4 (Inte

•inr Surface)

' ' "1 •~~ MonBc ■-•"Monftc

V

trpas. 3 ►rpos. 4 (Inte ior Surface)

s ̂-^-vs.^m'

10 15 20 25 30

Time [d]

PrcjDCt Prijcrt aim Report I Cajci 1: Rick Vcnocr Moits! - 1-VE NO.10-AC

127

o

3

Q. E .0)

30

20

• MonRorpos. 1 (Exteriw Surface) ■ Monftorpos. 2

6 3 X

$

DC

100

75

50

25

' 1 1 r "~" Monitorpos. 1 (Exterior Surface) —•-MonRorpos. 2

10 15 20

Time [dj

30

Prcjod: Prcicd ard Report I Caatr 2 Sp4\Kfi Stcaig Wxfcl - 2-NVa-*KS-1-AC

128

30

„ 20? O

&

e ca. E

.«>

10

Is E 3 X $

-10

100

75

50

25

"■~ MonSorpos. 3 «—- MonSwpos. 4 (Interior Surface)

"~>" MonBc — MonKc

irpas. 3 irpos. 4 (Inte

r

■ior Surface)

L -y"'^ -spî::^ *^s=

10 15

Time [dj

20 25 30

Prcjc* Prcjcr! ari) Report fCaio 2: Eff-KO EkSnj Mxfcl - J-N-j^-Nn-t-AC

129

30

« I—•

e E <D Q. E (2

■o E 3 X $ « o

1 i r ' Moni?orpos. 1 {Exterior Surface) •MontSofpos. 2

14.4 19.2

Time [d]

28.8

Picjctt Prc\oTt and Report I Case 2: Sprjtn Siding M:>dcl - Z-Wi/S-MO -i-AC

130

30

^ 20 o

& 3

E Q. E .©

10

-10

• MonBoipos. 3 ■ MonRorpos. 4 {Inlerior Suitace)

■smn

E X S -«> TO e

100

75

50

25

""" MonRt —"MonRt

>rpos. 3 >rp-3s. 4 (Inte ■ior Surface)

1

^ —^ ~

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prclc* Prcjca anit Kcfnttt CasD 2: Sf<\Ki'î*¥M0M F

10 15 20

Time [d]

Projott Projoa ard Report f Casi! 2: SfftKe S«lng Mxfcl - I-NVE-ND-T-AC

132

30

^ 20 O

s <D O. E .2

10

E 3 X $

-10

100

75

50

25

"~~ MonRc —-MonRc

trpos. 3 irpos. 4 {Inte

r-

■ior Sufface)

—• MonRc — MonRc

1 ! ►rpos. 3 rpos. 4 {Inte ior Surface)

^

10 15 20 25 30

Time [d]

Prcjott Prc|c9 and Rtport (Can: 2: S^.Kn SWnj Mrfrt - J-MijBNO-T-AC

133

30

I MonRorpos. 1 {ExIerioT Surface)

•—-Montorpos. 2

O g

&

1 (D O. E

-10

100

75

3 X 50

$ (0

§: 25

Prcjott Pnrjoa ara RapDrt f Cajli Z Spfjts Sang Mllsl - 2-NVS WD-IO-AC

134

30

„ 20 f O

MM*

& a> a. E

E 3 I

-«> W e

CC.

—* Monfiorpos. 3 — MonRorfKJS. 4 {Interior Surface)

10

-10

100

75

50

25

"~~ Monilc "—"MonSc

V

1 ►rpos. 3 upos. 4 {Inte ior Surface)

s 10 15

Time [d]

20 25 30

PrclB* Prcjoa aim Ropoit (Case 2: Efr.K« EH113 M>*! - 2.N';B-NO-10-«:

135

o e

"e 3 E a. E

■D ■£ 3 X $

10 15 20

Time [d]

Prcjc* Prcjotl ans Report ^Caso2: Eprj:c Eianj Wa*;(. J-VB-MJ-I-AC

136

30

^ 20 O

& 3 *-* E OL E .2

10

E X

I

-10

100

75

50

25

• MonRtsrpos. 3 •Moniiorpos. 4 (Inlerior Surface)

1 •~~ Moni?c — MonSo

1 trpos. 3 irpos. 4 (Inte •ior Surface)

L Xss

0 5 10 15 20

Time [d]

25 30

Prc-jDCt Prc^Dflt aiMj Report i Caris 2; S^jza Skflng Macte! - 2-VB-Na-l-AC

137

30

3 E o Q. E i2

E 3 X $ TO

■ MonSoTp^DS. 1 (Exterior Surface) •MonBoipos. 2

28.8

Prcô* Prcjcdtard Report i'CasD 2: EpcKfi swing W>dlc?-2-VBMa-4-AC

138

o & 3 c o. E

30

20

10

-10

* Moni?or[K)S. 3 • MonrSorpos. 4 (Interior Surface)

is E 3 X

o

100

75

50

25

-—MonBc •—-MonRc

HP0S. 3 jTpos. 4 (Inte ■ior Surface)

^ iscm ^

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prcjisit PrcjcO ami Rcpoit !■ Ca=o 2: E(:r.K« SMnj Mxfcl - J-VB-NDJI-AC

139

o ¥ c v> a. E .«

1 3 X 5 «

60

40

20

—— MonKo — MonRo

1 1 1 rpM. 1 (Exteriw Surface) rpos. 2

■

10 15 20

Time [d]

Prc-JO!± PrcjBrt ard Report {Cast* 2: Sffîcfl Skanp M>:fct - 2-VB-Na-7-AC

140

30

O

E m Q. E .2

10

£ 3 X $ TO m

-10

100

75

50

25

— MonRc — Monilo

trpos. 3 irpos. 4 (Inle ior Surface)

^—„-_-^_j

———^ •"" MonRc — MonRc

V

►rpos. 3 irpos. 4 {Inta

1

■ior Surface)

v^ ^

10 15

Time [d]

20 25 30

Prcjort Prcêrt ara Report ( CJSC 7: Eprjtc Siian^ M>*:3 - 2-VB'NO-7-AC

141

o

1 O. E

E 3 X 5 TO

75

50

25

i ■— MonHc "MonSc

trpos. 1 (Ext »rpos. 2

T arior Surface) i 1^ iffl k 1

• f "11

10 15

Time [d]

20 25 30

Pre]Dct Prcjool and Ropnrt.' Case 2: SfAco sauj VbiH - 2-Va MHIO-AC

142

30

p ¥ 3 & ffi Q. E

20 f'

1 1 *~~ MonKorpos. 3 — MoniSoTpos. 4 (Interior Sutfacs)

10

-10

"S E 3 X 5 ffl c

CC

100

75

50

25

—— MonRc — MonrSo

krpoB. 3 trpros. 4 {Inte •ior Surface)

^

10 15 20

Time [d]

25 30

Prcjo* PrclBtf am Hoân lCAUD 2. Sprjci: SKSnaMxfcJ -2-VSMD'IO-AC^

143

Appendix 2 - Minneapolis Test Data

144

o p

3 s o I

E 3 I

I

24

12

0

-12

-24

-36

100

75

50

25

1 1

—~ MoniSorpos. 1 (Exts —-Monaorpos. 2

1

r— rior Surface)

r

^

v7S\ t^V

%

Vir n

H'^\ /\ Al< i/^ V V

%/ V \ vv VV

1 •— MonRo — Monfto

1

rpos. 1 (Exte trpos. 2

rior Surface)

. rntrA V- ' T "^ A,/' Jy ry

\ If 1 r

10 15

Time [d]

20 25 30

Prejert PfcêrtardReport 1 Casn 1:BrckVenisprModn!- 1-N\'BM 1-,«:

145

o c

& 3

<D Q. e

30

20

10

-10

1 1 • MoniSorpDS. 3 • MonKorpos. 4 (Interior Surface)

■D E 3 X 5

•■a m e

OH

100

75

50

25

1 "~~ Moni?c — MonBc

i—

rpos. 3 trpras. A (Inte •ior Surface)

L. ^^:::^ ^w"^ -,.-—-J w"-*—

'^

10 15 20

Time [d]

25 30

Prc|e!* Prcjnrt and Report f Case VefckVannorMtsdol- 1-N\'BM-1-^

146

o ft ^ ¥ 3 *^ E o Q. E |2

100

E 3 X

$ S3

"~~ MonRorpos. 1 (Exterior Surface) «—-Montorpos. 2

Prelo* Pro|ca nrd RipoTt / Caso 1; Beck Vcncor Modol • l-NTO M J-AC

147

30

^ 20 O

& 3 E a> a. E |2

&■

E 3 X ?

-■aa a <D

10

• MonRorpos. 3 " MonRurpos. 4 (Interior Surface)

=u=

9.6 14.4 19.2 24.0 28.8

Time [d]

Prslo* PK)e:( and Ripoit (Cam 1; e<T.V Vonocr Model - l-NV-E M 4-AC

148

60

„ 40 O

3 E e a. E

TJ E 3 X S re

20

-20

100

75

50

25

^ 1 ,

—" MonitariKJS. 1 {Exterior Surface) ~—"MonfSorpos. 2

f^ A

1 1 r "~ Monitorpos. 1 {Exterior Surface) ""Monfiorpos. 2

10 15 20

Time [d]

Prciott Prcjart and Report / CJSE 1: Err> Veneer Mattfti - 1•N^'B M-7-AC

149

30

O

ffi E

10

E 3 X

I

-10

100

75

50

25

— Moni5c — MonRc

►rpos. 3 ►rpos- 4 {Inte 'ior Surface)

«— MonRc ^"MonRc

krp-DS. 3

irpos. 1 (Inte ior Surface)

N.

10 15 20

Time [d]

25 30

Pro|B* Prcjca ana Rcpoit ? Cam 1: Beck VoncDr Model - 1-N\'E M TJkC

150

30

O a

& 3

c E

"~* MoniJorpDS. 1 (Exterior Surface) — MonrSarpos. 2

E 3 X S « O IT

100

75

50

25

1 , r

-«~ MonRorpas. 1 (Exteriw Surface) i"~'"MonRorpos. 2

10 15 20

Time [d]

Prcjctt Projcrt and Report f Case 1: Bf ck Vcnimr Modol • 1.N\'e M 10JVC

151

30

„ 20 o

e a. E

10

-10

1

■""' MonRo •—"MonRo

— fc -

rpos. 3 irpos. 4 (Inte ior Surface)

fc<^Ûi^*****i

■g £ X

100

75

50

25

1

"—" MonRo ■—"MonRo

rpos. 3 HpDS. 4 (Inte nor Surface)

L .^2::;s» kCkMaeprf ..cC: .-^

10 15 20

Time [d]

25 30

Prcjert P^c^Dfl^ ard Report i' Casts 1; BrcK VBneer MortoJ -1 ■N'l'B-H 1C~AC

152

24

O

¥ 3

{° e o. E -12

-24

-36

— 1 — MonBorpos. 1 (Exts —"Monitorpos. 2

1

ricjr Surface) r"-

1

f \\J\ 4 ' 1 V ̂ Jpx

4^. J n % V ̂

f t Vv W\f

100 "~~ MonRorpos. 1 (Exterior Surface) "—-MonKiwpos. 2

^ 75||f—

S £

as

Q:

10 15

Time [d]

Prc\tiXt Pfcjcct and Report ("Caan IrBfcVVennRrMQdot. 1.VB-M-1-/«C

153

o ¥ 3

& CO Q. E |2

30

20

10

1 3 I ?

■■ta

m

-10

100

75

50

25

"~ Moniiarpas. 3 ""Montorpos, A (Inlerior Surface)

*— MonBc — MonRc

krpos. 3 ►rpos. A (Inte -ior Surface)

v-'''^ >»•—»•-.

....^ -^

MWMB, —"-1^!!^

0 5 10 15 20 25 30

Time [d]

Prcjorl: Prcjca arat Ropoit f Cast 1: EfcV Voimar Koaol - l-VE-M-IAC

154

o ¥ 3

E

E

is E 3 X f

-■a

30

20

10

-10

100

75

50

25

— MonRc —-MonRc

►rpos. 1 (Exteriof Surface ►rp-as. 2

I

\ t tlJ^V .,

\

f^ ^ ^

ri TI V " ' 1 1

•~" MonRt — MonRc

jrpos. 1 (Ex1« ^^pos. 2

i rior Surface;

If 1

1 rt

*

A i r 1

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Pralod: Prîttrtard Reports Case IrBrck VoniserKoilo!- 1-VEM4-AC

155

30

^ 20::!

e 3 E o Q. E 12

£ 3 X

S «

10

-10

100

—— MonRc "—MonRc

vfp-os. 3 >rpos. 4 (InlB ior Surface)

50

^- 25

"""• MonRorpos. 3 — MonRarpos. 4 (Interior Surface)

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prcloa: Prcjna KiiJ Hcport f Case 1: Bret Voiwor Model • 1-VE-M 4 JiC

156

o & 3 E m Q. E

60

40

20

-20

100

1 i r ' Monrtorpos. 1 {Exterior Surface) ' MonSorpos. 2

•o 1 3 X

-■s

> MonRorpos. 1 (Exterior Surface) »MonRorpos. 2

ProjBti: Prcjncl Ofid Report ^ CasD liE^ckVcnserMoilc!- 1-VE-M-7-AC

157

30

O

E a> a. E

10

E 3 X ?

o

-10

100

75

50

25

' MonRorpos. 3 " MonSwpos. 4 (Interior Surface)

! —-MonRo — MonRc

i—

upos. 3 hrpos. 4 (Inte •tor Surface)

L 10 15 20

Time [d]

25 30

Prcjoct PrcjDct aird Rcpoit ^ Cisc 1: tfrX Vrniocr Model - 1-VEM T*C

158

30

^ 20 O

& 3 E « Q. E

is E 3 X 5 V W

10

-10

100

\ 1 r- ■~~- MonftoTpDS. 1 (Exterior Surface) "—"MonHc ffpos. 2

.iJL \ . 1 1 ^MrW k |J% Ittf IIÎV 1

UlJf fW mrlJ r li \ ||l 1 ^ Njf I 1

-~~ MotiRorpos. 1 (Exterior Surface) li~"" MonSorpos. 2

Prcjcrt: PrcjDrt and Report t C«5D 1; Ef^cV Veneer rrfoiJc! - 1A'B-M lOAC

159

o &

1 o o. E

30

20

10

E X $

-■0

-10

100

75

50

25

—-MonHo •—""Monfio

1 — ►rpos. 3 ITpOS. 4 (IntB •ior Surface)

"~" MonBc — MonRc

apas. 3 irpos. A (Inte lor Surface)

u ="'—. . ■aMflH»«i^«M»

10 15

Time [d]

20 25 30

Pfcjoflt- Prcicrt am Report i* Case 1: Br^ck Vonoor Model - i-VB-M-IO-^^

160

o p

s 3

E « o. E

a- E 3 X 5

10 15

Time [d]

Prefect Prcind ard Rflport t' Cdll5 2: Spf^^fi SWlrt^ M>*H - J-W^B-^T-I -AC

161

30

^ 20 O

& 3

a. £

E 3 X S ffl e

10

-10

100

75

50

25

1 1

■ Monfturpos. 3 " MonRorpos. 4 {Inlerior Surface)

— MonKo •-•"MonSo

I

1

krFKJS. 3

kfpos. 4 (Inte •ior Surface)

I -N> ""^^

10 15 20

Time [d]

25 30

Pn;}ocfc Prcjocland Report (■ Case2; Ec^JTfl Sv3n^*A-xk\ -Z-W/a-M-l-AC

162

30

O 6

3

a. E

—■ Monflorpos. 1 (Exterior Surface) ^-MonRorpos. 2

-lU

100

£ 75 i- T3 £ 3 I 50

s ■iR w a: 25

■""" MonRorpos. 1 {Exterior Surface) —"MonRoTfras. 2

9.6 14.4 19.2

Time [d]

24.0 28.8

Prclnrt: Prcjcct and Report.' Case 2 SpfJô Skflng M»*:i - 2-*f/S-\V4 AC

163

30

^ 20

<D Q. E

10

2> |D E 3 X S

-■s re a>

-10

100

75

50

25

— MonRc •""Monfic

jrfKJS. 3 >rpos. 4 (Inte 'ior Sufface)

-■—•mf—^'

"~~ MonKc — MonRc

jrpos. 3 itpos. 4 (Inte

r-

■ior Surface)

[

L -KSZC

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prcjo* Prcjoa »ia Ropoit f CasB 2; Siyjrii sang M>*l ■ l-tt/B-V-CM:

164

o ft

e 3

E Q. E .©

60

40

20

-20

100

1 ,

•~" MonrSorpos. 1 (Exterior Surface) —■-Mon'rtorpos. 2

JIAAAR AJM Y* f^ /.A AAAiUi fi'^r r^ r^T

1 3 X $ iS

• Monawpos. 1 (Exterior Surface) ■ MonRorpos. 2

PrclB* PiDlDrt and Report I Casn 2: Eff-cc SitSiij Mibd - 2-WiB.W-7.AC

165

30

r^ 20 P

& 3 1 a. E m

10

E X

? m «>

-10

100

75

50

25

—~" MonKc 1 irpos. 3 rpos. 4 (Inte ior Surface)

•"^ Monftorpos. 3 — MonSarpos. 4 (Interior Surface)

s^_^^_j_;

10 15 20

Time [d]

25 30

Prclcrt: Prc|oa orit Ropon I Case 2 Sfry.t: EkSrij Mi*:1 • 2Jfj'EJJO-T-AC

166

30

O

s *"*

a> Q. E .2

1 1 p

■-"- MonRorp-3B. 1 {Exterior Surface) —» Monrtorpos. 2

E 3 X $ w <D

100

75

50

25

0

1

*~~ MoniSorpos. •-~"Moni!orpos.

-- 1 1(Exte 2

rior Surface)

U-- T1"

-( rl ¥

# / f

"

1 1 f

0 5 10 15 20

Time [d]

25 30

Prajuct Prcicfl ard Rfijjort t" Cacc 2: Ep<.t:fl Sfcang M>5te( - 2-*J'/aAI-1{J-AC

167

30

„ 20 O

3 E a. E

10

E 3 X 5 iS a>

-10

100

75

50

25

—' MonRc "—"MoniSc

trpas. 3 >r|K)S. 4 {Inle

1

■ior SuTfacE)

— MonRc """MonRc

1 ■■'

rpos. 3 irpos. 4 (Inte

1

lor Surface)

^b^^ ^^^

10 15 20

Time [d]

25 30

PrcHott PwjBrt af^d Report.' Casr 2: Spr.Ko Siding 9Ay±i ■ 2~f^'M\^^Q-AC

168

o 0

&

& <D Q. £

E 3 X 5 as TO

IT

10 15 20

Time [d]

Prolta: Prejetl and Report i Case 2: Sprjri! SKlnj M:*) - 2.VB !tM-*E

169

o ft

"i* 3 E Q. E

30

20

10

E 3 X

S ■■c TO a>

-10

100

75

50

25

■ MonRorpos. 3 ■ MonRofpos. 4 (Interior Surface)

—" MonSc ^-MonRo

\

1 ' ■""•

►rpos. 3 trpos. 4 (Inte

i

■ior Sufface)

L ~^_ =^ ■L_—.

10 15

Time [d|

20 25 30

Prc(ai:t Pmicrt and Rnpnrt {Casit 2- Sprjrc EWng MxJct - 2-VH r/-1 .AC

170

30

O

s a. E

•5 E X S iS DC

"■ MonRorpos. 1 (Exterior Surface) ""Mon'torpos. 2

14.4 19.2

Time [d]

28.8

PtniQdr. Prc(Drt ard Report / Case 2: Spr.KC SicSng M>:fc^ - 2-VB^'-4-AC

171

o p

¥ 3 E <D Q. E

■o 1 X 5 i5 Q>

30

20 ::^

10

-10

100

75

50

25

—— MonHc •—"MonRc

jrpos. 3 ^^pos. A (Inle

1 ~

•ior Surface)

1

^^îmmmfl^*

"~~ MonBt — MonRc

{

irpos. 3 irpos. 4 (lots ■ior Surface)

1

V

4.8 9.6 14.4 19.2 24.0 28.8

Time [d]

Prciod: Prclnrf and Report ^ Case 2: Sff.KB Skanj Mais) - 2-VB-M^ ftC

172

o

&

E « o. E .©

60

40

20

-~" Monftorpos. 1 {Exlerior Surface) — MonSorpos. 2

-20

E X

re

100

75

50

25

•""■ MonRorpos. 1 (Exteriar Surface) — MonilorfSos. 2

10 15 20

Time [d]

Pfcôrfc Prc^nri ard Report / Cdcci 2: Ejy.KC SWng V>*;! - 2-VS M^T-AC

173

30

O

¥

£

20 5^=

10

E 3 I s w

-10

100

75

-~~ MonHorpos. 3 ^-Mon3c3T[X)S. A (InteriDr Suiface)

50^

25

*~~ MonHc — MoniSc

1 trpos. 3 ffpos. 4 (Inle ■ior Surface)

^

10 15 20

Time [d]

25 30

PrcjD* Prcjnd and Report f Caso 2: Eff-ici! SKSrij Mxfct - 3-VE-W r.AC

174

30

O o

& 3

e Q. E

10

£ X S

-10

100

75

50

25

—- MonRc

1 ^

Hpos. 1 {Extericff Surface) rpos. 2

1

.Hi.

(W f^ \l\^ r\ ̂̂ ntiv ™ 1 " 'V lif \

\\ w 1 ,

• MonKorpos. 1 (ExtGrior Surface) • Moniforpos. 2

10 15 20 25 30

Time [d]

PrcjBct: Prcjed ard Rnpnrt i* Caaa 2 Spr.KR SWna Mxic! - 2-Va^*^-10-AC

175

30

O

& 3 E

E

1 3 X $

S3 «

10

-10

100

75

— MonRc — MonRc

krp-os. 3 ►rpos. 4 (Inte •ior Surface)

mmm^^^^'^'

~~~ Moniio —""MonHc

I

i ■■■'

srpos. 3 fpos. 4 {Inte 'ior Sufface)

L 50^*-—'

25

10 15

Time [d]

20 25 30

Prcled: PrcjDrt and Report i" Caso 2 Sprjcc S»3n3 MatteJ - 2-V&W 10 AC

176

Appendix 3 - Roanoke Test Data

177

60

^ 40 O

&

a. E

20

-20

100

1

•~~ MonSc — MonRc

1

rpos. 1 (Exteriur Surface) ►rpos. 2

f% ?^^Y ̂ i^c?^ *>iry\^ *-i».<-V 1' '^ V IT^ ''\)ug^ /pv A/V

E 3 X S

e

• MonRorpos. 1 (Exterior Surface) ■ MonBorpos. 2

10 15 20

Time [d]

30

PrfljBd- Prcjoct aril Report i Case 1: Brclr VcinocT Madol - l-NVTS R 1-A^

178

30

O

e o Q. E .2

20 S

10

E X 5

-.0

Si

-10

100

75

50

25

—-• MonRofp-DS. 3 —-MonRorpos. 4 (Interior Surface)

1 •"" MonRc "^-MonRo

I

... rp-3S. 3 trpas. 4 (Inte lor Surface)

*~~*^;

10 15

Time [dj

20 25 30

Prcjc* 9\c\t!^ ard Rcpoft t Case 1: BrcK Vcnoor Moda! - 1-m'E B- 1-AC

179

o & 3

E o Q. E

30

20

10

-10

100

i 1 1

—• MonRorpos. 1 {Exterior Surface) 1 """MonRorpos. 2

1 kA^Lxi L ft mm^\

f i 1 1IWITV ' " 11^ \\l L AWu Vv^ \\\^l^. Av 11 Jl^Jff f '^H'i ff w fvj ̂

V

3 X ? X3 m e Q:

0 4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prcjiozt Prci&dr and Reports Case 1:Bi"ck VenoorKntlfil- l-NV'E F-4-AC

180

30

^ 20 O

&

Q. E

10

-10

' MonRwpos. 3 • MontorpoB. 4 {Interior Surface)

E 3 X $ «

100

75

50

25

•"~- MoflRorpos. 3 — MonRorpoE. 4 (Interior Surface)

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

PfCiort Prcjua ard Report ^ Case 1; Brck Venncr Modal • 1-MVE-R 4-AC

181

60

^ 40 O

&

« a. E

20

-20

100

— MonRo — Mon'rto

krpos. 1 {Exte kfpos. 2

>rior Surface)

mmm^mMm0^ '■ f ■ f V V ' »»

r 1 r —" MonJSorp-as. 1 {Exterior Surface) —"MontorfKJS. 2

is E 3 X $ «

25 30

Prc|Brt PfcjoctanfJRiipcrti'CaSB t:BrckViinofirMado!- l-N'.'B-R-7-yy:

182

o

& O Q. E

30

20

10

1 3 X 5

-10

100

75

50

25

1

""" MOHRD — MoniSc

1 rpos. 3 rpos. 4 (Inte ior Surface)

—^..^-^^—™_«^

! •~~ MonfIc — MonKc

ffpos. 3 rpKJS. 4 (Inte ior Surface)

s

10 15 20

Time [d]

25 30

Prcjea." Prelect OPO Report / CJEII 1: Ei'rA Vcnnor Moilfi! - l-KVE-fl-T-AC

183

30

^ 20 O

«^ E o a. E •2

£ 3 X 5

JO o

10

-10

100

75

50

25

1 1

■— MonRorpos. 1 {Exterior Surface) — MonRorpos. 2

Ai

1 w \

Jip 4|| if in iv ¥ f

1 , r

—"• MoniSorpos. 1 {Exterior Surface) —" MonPtoTpos. 2

f4—

10 15 20

Time [d]

Prciet:t: PfclDd and RcpGrt i*Case ^■.Srck Vencnr Mortol• 1-NVBR 10^C

184

o o

& 3 *^ & O Q. E

30

20

10

•• MonRorpos. 3 ■ MonKoTpos. 4 {Interior Surface)

■D E 3 X $

10 15 20

Time [d]

Prclo* PKicrt and Report i Case 1: Ef-cV VonnoT MfldDl - l-NVE RIO-AC

185

60

o e 3

E 20 m o. £ .©

-20

100

—— MonRc — MonRc

1—^—

rpos. 1 (Exterior Surface) itpos. 2

1

hft A\ fv(r^ ii7h^""V VNTJ^^ '"•'»<f"^ f' ^ V ly^ ''VA? Ipv ''^^

' Moni!orp.3s. 1 {Exterior Surface) • Montlorpos. 2

£ 3 X

•■o ffl «>

10 15

Time [d]

Prcjact Prcjort and Rcpctt i' Cast 1: E^-cti Vonccr Model - l-VB-R-I^C <Nn* Orfcarr. VB Locat an)

186

o e 3

(S

E

30

20

10

-10

• MonSorpos. 3 • Monr?(iip>os. 4 {Interior Surface)

3 X

$ TO

100

75

50

25

— MonSc

1 krpos. 3 )rpos. 4 (Inte ■ior Surface)

^

10 15 20

Time [d]

25 30

Prcjcct PrclBCtard RflportfCast! 1: Br'cVVcncDrMatle!! - 1-VB-R-1-AC (Ncr* OrtcaisVB Localan)

187

o 0 >||. mi

e 3

E

30

20

10

-10

1 i 1 —• MonRorpos. 1 (Exterior Surface) 1 ~ "MonHt srpos. 2

1 1 Aklt L ft mm^<

' 1 1 11*17'' "^ iiv * I L ft Am/ Vv^ N.kW \ IKm. LL.V JiiJff f '^H'ji

1 n w f^ ^ V

§1 a- E 3 X ? B

14.4 19.2

Time [d]

28.8

PfC^fttt Prcjnrt ard Report i"Case 1: Brck VEnnerMadol - l-VB R-4-AC <Nc* Crt:ars ^/B Locrfton)

188

o c

& 3 E m a. E .©

E 3 I

$ TO

30

20

10

-10

100

75

50

25

■ MonRorpos. 3 ■ MonHorpos. 4 (Inlerior Surface)

i 1 r "~~ MonSorpos. 3 —" MonfS&rpns. 4 (IntBrior Surface)

■*g'Jin<gWoij«^

4.8 9.6 14.4 19.2 24.0 28.8

Time [d]

Prcj0rt PrcjDOl ard Rfiport r Cdsc 1; ErcV VunonrMorffl! ■ 1-V& R-4-AC <Nir* Orfe>aiE VB Ucatcn)

189

60

„ 40 O

£ 3 E Q. E

20

— MonRc — MonSc

1 WfKJS. 1 {Ext' Hpos. 2

I 'rior Surface]

1

ummmifMm}^ ' 1 » V —^~- 1 »

e 3 X 5 (0

5 25

10 15 20

Time [d]

Prcjort Prclca ard Rflport r*CasD 1: E^ck VononrModel - 1-VB-R-7-AC<No» Orfcars VB Iccsion)

190

30

„ 20 O

& 3

a> Q. E

E 3 X 5

10

-10

100

75

50

25

•■"" MonilMpos. 3 — MonKorpos. 4 {Interior Surface)

VterMM Mter<^l«^M I

— MonSc ^-MonRc

1 ►rpos. 3 ►rp-os. 4 (Inte

r

•tor Surface)

v^ ̂ --^

10 15 20

Time [d]

25 30

PrcjBrt: Prcjo:! wid Report (C^wc 1: ErcV Voniser Mode! - 1-VE-R-7-AC <NfiBf Grte-a^s VB Locarton)

191

30 1 i r •■"" MonHorp-os. 1 (Exterior Surface) '^" MonKorpos. 2

O p

8 3

c (D CL E

E 3 X $ w

100

10 15

Time [d]

PmjDcJ: Pfcjea ard Report / Case 1; BrcV Vcncor Modol - 1-VB-R-1C-AC <ND* Orfcnra VB Ucaaan)

192

o

1 9

I

E 3 X

«>

30

20

10

-10

100

75

50

25

—— MontSc —'-MonRc

rpos. 3 wpos. A (Inte 'ior Surface)

"~" MonBc ~- MontSc

wpos. 3 ►rpos. 4 {Inte

1

'ior Surface)

V.J2^ -^^^ ---^

10 15 20

Time [d]

25 30

Prcjed: P^:Î!Cta^d Rcpoft CCasc liBrck VoncBrMotlo!- 1-VE R-lC-AC(Ntnii OrJcans VH locifion)

193

E

60

40

20

1 , p

"-~ MonRorpos. 1 (Exterior Surface) —-MonSorpos. 2

-20

100

{ o^^^^L;^ p^^

"■"" MonrSoTpos. 1 {Exterior Surface) "--"Moniieffpos. 2

Prcjnct: Pn:|i!!S and Report / Ca5G 1; Erck VanRcr Model - 1-VE-R-l-AC ^MJ^PGapotl; VH locaflonj

194

30

^ 20:3 o

E e Q. E

1 I 5

10

-10

100

75

50

25

"~~ Monilc — MonKc

1 >rpos. 3 »rpos. 4 (Inte

1

■iar Surface)

"■"" MonRc — Mont»c

r— ■■■■ srpos. 3 jrpos. A (Inta ior Surface)

îsrsS ̂ ^r:i^ --JMTT —— ——i.«> ^>i>«_»

10 15 20 25 30

Time [d]

Prcjtftit- PrcjBCt and Report/CaEfi 1:8?".»:*.Vonfiiif Hiiilcl- i-VB-R-l-AC^MkrrenpQKVB Loca'JcnJ'

195

o

30

„ 20

E

10

-10

100

E 75 £:■ V E 3 X 50

5 33 ta

DC 25

1 r -"— Moni?CH-p3S. 1 (Exterior Surface) —-Monfforpos. 2

*~~ MonRorpos. 1 (Exierior Surface) •"■"MonRoTpos. 2

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prc^Btt: Prcjcrt and Rcpart / Caso l: BCcK Vcnoisr Made! - 1-VB-R.4-AC {MimoapaK VB Locafinn)

196

£

a. E ,2

30

20

10

&■

•a E 3 X ? W

-10

100

75

50

25

— MonRt —-MonPIt

i jrpos. 3 jrpos. A (Inte

1

■ior Surface)

i ■-

"~" Monilt "—"Moniit

i

1 jrpos. 3 jrpos. 4 (Inle •ior Surface)

1

LJ

4.8 9.6 14.4 19.2

Time [d]

24.0 28.8

Prcjorfc Prcjortard Rcport^CaBnliBrcfc: VcnenrModn!- 1-VB-R-4-AC<MirnisapoliiVH Locaflon)

197

60

^ 40 O

e 3 ^^ (° O Q. E |2

20

-20

100

1

——■ MoniSc ~-MonRo

r- wpos. 1 (Exte *rpos. 2

rioT Surface] 1 ■ ■'

mlhmmfSum0i ' » » V V ' f»

' MonRcwpos. 1 {Exterior Surface) »MonRorpos. 2

10 15 20

Time [d]

Picjfl* Prcjort art! Ropott f Casp 1: Erck Vcnortr Mods" - 1-VE-R-7-AC ^MI-nfiapoK VB Loca«nn)

198

¥ 3

a. E

1 3 X 5 TO a>

30

20

10

-10

100

■—MonRc —-MonSc

1 upas. 3 trpos. 4 (Inle

1

'ior Surface)

-" MonitoTpos. 3 ■" MonRorpos. A (Interior Surface)

10 15 20

Time [d]

Prcjoci Prcjert aril Report /Case 1: Brck Venosr Mads! - 1-VE-R-7-AC <Mif5ncapQlr, VB Locjaon)

199

30

O

Q. £

E X

■■e

1 1 r "~" MonRoipos. 1 {Exteriw Surface) — MonfSwpos. 2

10 15 20

Time [d]

PrajDCf: Prcjert and Report ('Casrs 1: &"^rk, VflnocrMode! - 1-VB-R-1P-4C<MrrflapQSE, VB LncaSan)

200

o & 3

E Q. E

30

20

10

E 3 X

-10

100

75

50

25

— MonRc — MontSc

krpos. 3 wpos. 4 (Inte

1

'ior Surface)

mPif'' *i^

""" MonSc — Monilc

I

►rpos. 3 irpas. 4 (Inte 'ior Surface)

L 10 15 20

Time [d]

25 30

PrcjcttPrcjBCt art) Report ("Case ItEfckVoneor Mortal. l-VB-R-lO-AC^MrrfiapoSuVH Ucoflon)

201

p

E n. E

if

E 3 X ?

S3 JS

10 15 20

Time [d]

Prcifict Pn:jcd ard Report i* Case 2: Sf^rjce EWIng M:Kfc^ - Z-Wi^f^-l-AC

202

o

& 3

C Q. E

30

20

10

-10

— MonRc — MonBc

1— ffpos. 3 >rpos. A (Inte inr Surface)

100

•o E 3 I

Pnzjoct Prc|ert and Report/Case 2: SfxiKc sang Mrf£l.2-M'-/a-K-1"AG

203

o p

3

c Q. E |2

^• is £ 3 X S

-■cs «

14.4 19.2

Time [d]

28.8

Prc|Brtr Prcjor* arfl Report / Case £: Sprxa SWIng WyM . 2-W/B-R-4-*£

204

30

„ 20 O

3 & <D O. £

5- Jo E 3 Z 5 « or

10

-10

100

75

50

25

— MonrSoffKJS. 3 -•MonRoT[K)S. A (Interior Surface)

1 —— MonSt — MonSt

i' >rpos. 3 jrpos. 4 (Inte

1 1

■ior Surface)

H WliM'«g»i _____ !^!^!S^

4.8 9.6 14.4 19.2 24.0 28.8

Time [d]

PrclctJ: Prcjcrt and Ripoit I Casi! 2 Epcjce Skiing Mj*:l ■ 2-fWH-R-4-*C

205

o p

¥ 3

a. E

60

40

20

-20

100

1 1 — MonRorpoE. 1 (Exterior Surf ace; —-Monitofpos. 2

1—

f0 m MM0 ̂ m

K' f » r y V 1 V

E 3 X

? iS

1 r "■"• Montorpos. 1 (Exterior Surface) ^-MonSorpos. 2

10 15 20

Time [d]

Prejoa: Prclod ard Report ^ Case J: Sfojcs Sanj M:>*J - 2-W/H-R-7JIC

206

o e 3

a. E

30

20

10

E 3 X S

-10

100

75

50

25

— MonKc — MoniJc

hrpos. 3 H-fKis. 4 {Inle 'ior Sufface)

a^"^"^*^"^

"~~ MonKc — MonRc

1 ►rpos. 3 ►rpos. 4 (Inte •iar Surface)

s.

10 15

Time [d]

20 25 30

Prciact Prcjort and Report {CaKc 2- Spr-Cfl SKSng Wî:) - 2^/B-R-7.*C

207

30

^ 20 CJ

£ 3 *>* 10 e t (D h-

U

-10

100

£ 75 £? ■D

E 3 X 50

5 -.e CO

^ 25

' MonRorfvas. 1 (Exterior Surface) ■ MonRorpas. 2

10 15 20

Time [d]

30

Projett Prcjcct and Report (Casr 2 Sprjce Sl-ang M>3c^ - 2-MV9-R-10-AC

208

30

^ 20 O

e E (D

I 10

-10

1 ,

■ MonRorpos. 3 "MonSorpos. 4 (Intarior Surfacs)

E 3 I f

100

75

50

25

«— MonRc — Monilc

1 1 Ifpos. 3 irpos. 4 {Inte ior Surface)

^ -^->^

10 15 20

Time [d]

25 30

Pn:}orit PrciDaaPilRfipartfCa5c2:S?)rjCflSi5rtj|M5*:l .2-NV5-R-10-AC

209

o 0

& 3

e n. E

E 3 X 5 W

10 15 20

Time [d]

Prdo* Prc^BCt ana Report I Caso 2: Sprxo SUnj Mxfcl ■ 2.VH S-1-*C INr« Oitcans VB Lorato-ll

210

30

^ 20 O

& 3

E

10

-10

-—• Moni!c — Moni?c

rpos. 3 r|X)s. 4 (Inte 'ior Surface)

—'"^."—"■■I-II—I--J ——-™~-~*™---i --—— ~™

1 3 X

re <D or

100

75

50

25

•"~* MonHc

\

1 trpos. 3 wpos. 4 (IntB

1

ior Surface)

L mtm^mm^mmmm

10 15 20

Time [d]

25 30

Prcjeat Prc-fBd arrt Hapcrt i'Casts 2: Sprj:*! Sang M^dcl - Z-VH-R-I-AG (Nc^-vOrtoant VB LxaUanl

211

30

„ 20 O

E

E .2

10

-10

—I i

—— MonRorpos. 1 (Exterior Surface — MonRcjrpos. 2

1

1 k 'i-h K.Jr'-.^j^^^ (^ffH \i i 1 M V IfJ ^

100

E 3 X ? re

•— MonRorp-DS. 1 (Exterior Surface) — MonRoTpos. 2

28.8

PfcjKcfc Prc^ftct and Bfipnrt ^ Case 2: Sfr-KO SkSf>g MadcJ - 2-Va-R-*-AC {New Ortfiant VE bKaUyiJ

212

o & 3 c a> Q. E

30

20

10

-10

" MonHorpos. 3 •MonRorpos. 4 (Irrterior Surface)

100

3 X

i 1 r MoniSorpos. 3 MoniJcsrpos. 4 {Interior Surface)

9.6 14.4 19.2

Time [d]

24.0 28.8

PrcjfiCt: Prcjna and Report / Caatj 2: Spra:*! Srtng \t^-M - 2-VB R-* AC |Ncw ■Driflans VB LocaH^'Î

213

60

40 o & 3

P 20 (D Q. £ .»

-20

100

1 1 -— Montiorpos. 1 (Exterior Surface] -""Monitrapos. 2

1

rt m MftAD (y* (m 0^ K^|-r r yn V Vj " 1*

' Monilorpos. 1 (Exteriof Surface) " MonRorpos. 2

E 3 X $ as

Pra(ra Prcjoct anil Report !■ CKO 2; EfTjô S«»nj M>*:4 ■ 2-VB-R T^C INy* CMoans VB Lo:aton|

214

o p

& 3

a> Q. E

30

20

10

-10

■ MonRorpos. 3 • MonRorpos. 4 (Interior Surface)

g::,

E 3 X

S W

100

75

50

25

"— MonRc — MonRo

V

trpos. 3 )Tpgs. 4 (Inte •ior Surface)

v^

10 15 20

Time [d]

25 30

Project PrajBtt and Report < Case 2: Spr,f:c SiSng MUa - 2-VB-R T.AC (ffew Oilcimc VB Localto-il

215

10 15 20

Time [d]

PrejD* Prefect and Report t Caivo 2: S|:r.»:c S^ng Ms*:! - 2-VB R-10 AC ff4:w Orioans VB Vo:aH>nt

216

o

3 *^ E a> a. E

30

20

10

-10

100

^ 75

E = 50

? as «

"~ MonSorpos. 3 "- MonRorpos. 4 (Interior Surface)

25

*~~* Monitc — MonHc

r- >rpos. 3 apos. 4 (Inte •for Sufface)

^ ..^

10 15

Time [d]

20 25 30

PrcjBCt Picioa ard Report I'Casis 2: SprvKO SteUng M^SW - 2-VB.R-10-AC (New Ortoanc VB loraltDnl

217

60

^ 40 O

& <D OL E

20

-20

100

■— MonRc <—MontSc

krpos. 1 {Ext€ npos. 2

riw Sutface)

N ̂i^t hui\ '-v^^ TfiCC; '"-?> *' '^ V liM '^VAJ^ i\r^ Ai\

■""• MonKorpos. 1 {Exterior Surface) — MoniSorpos. 2

E 3 X

10 15 20 25

Time [d]

Presort Prcjftd am Rfipnit / Caso 2: Sprjro B^Sng M>4:I - 2-VB-??-1 -AC lMnnEa:»:l)s VE tocatlsnl

218

30

^ 20 O

3

Q. E

10

-10

100

•~~ MonBorpos. 3 •—MonHoTpos. 4 (Inlerior Surface)

1 1 * MoniJwpoS. 3 ■ MonKorpos. 4 (Inlerior Surface)

E 3 X $ -s TO

Prcjo* Prljoin and Faport i' Case 2: Spr-Kii SHng M>*l - 2-VB R-1 -AC (IflnnomrfB VE Wcan:»i|

219

o p

IE 3

& O a. E

30

20

10

-10

100

1 1 1

"— MonrSmpos. 1 (Exterior Surface) 1 ^-MonHorpos. 2

1 1 iill li n Riofflfinnvi I 1 . 1 mn/vui • v \Ly< 1 UlU YC^ \ ANrnv_BN-J..kl,^^ ,«T«I 1 'li

i T m f

fN yw < V

■D E 3 X 5 J5 or

9.6 14.4 19.2 24.0 28.8

Time [d]

Prcjo* Prcjort and Report {Dane 2: Sprê SiCSnp MDCfcl • Z-VH-R-4-AC iMnnna^Nts VB t-^xatlcf^l

220

30

20 o

& 3

& 10 Q

.©

■o E 3 X 5 « a:

-10

100

75

50

25

—-• Monac — MonSc

jTpos. 3 wpos. A (Inle rior Surface)

•~~ MonRc — MonRt j-rpos. 4 (Inte

r ■

ior Surface)

Ij

4.8 9.6 14.4 19.2 24.0 28.8

Time [d]

Piciatt Prcjfifl ard Report (Casii 2: Sprxo sang W3dd • 2-VH.R .4-AC fft^nncaot^lE VE LKaH:^}

221

60

„ 40 O

15 3

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20

-20

100

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> MonBorpos. 1 {Exteriof Surface) ■ MonHwpos. 2

10 15 20

Time [d]

PrCjlDrt PfGjott ard Report t Caaa 2: SpriKn SkSng M>4H - Z-VB-R-7^C i1lfinnoa&at(s ^fB LocatVxit

222

o

IE 3 ^>* & a> Q. E

30

20

10

^5

E X ?

-10

100

75

50

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— —• MonRc — Monfic

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1 ■■■■

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■^^***^^ —B-^M

—• MonRc — MonRc

I

ifpos. 3 irpos. 4 (Inte ■tor Surface)

L 10 15 20

Time [d]

25 30

Pfojcrt Prcjort aniJ Rnport i Caso 2: SF-TJCC Stang M3.*:t - a-VE-R-TÂC (Mnnna&:*»5 VB locattcni

223

30

20

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g 75

1 = 50

^ 1 —— MonRwp'DS. 1 (Exterior Surface) ^-MonRwpos. 2

HI 1 .1

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^

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25

• MonSorpos. 1 (Exteriw Surface) • Moni!(srpos. 2

10 15 20

Time [d]

30

PfCicct Prcjca ard Report i" Cuac 2: SprvKe Siding Macfcl ■ 2-VB-Ria-AC (mnnaziyJH VE LOCHUITII

224

o ¥ E a. E ©

■5 E 3 X

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30

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100

75

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—■ MonRc — MonRc

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•ior Surface)

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10 15

Time [dj

20 25 30

PrcjDct Prciort ard Report (Case 2- Spr.Ko SitSng Mxld - a-VS-R-l O-AC (TWnTHsafix^k VB UxalkMil

225

5.0 Bibliography Achenbach, P. (1994). "General Construct'on Principles" in Moisture Control in Buildings. ASTM

Manual Series: MNL 18; Philadelphia, PA; 283-290.

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Anonymous. (1993). "Vapor Barriers under Slabs." Concrete Products. 96(3), 8.

Bordenaro, M. (1991). "Vapor Retarders Put Damper on Wet Insulation." Building Design and Constniction. 32(9), 74-77.

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Code of Federal Regulations (CFR). (2001). "3280.504 Condensation Control and Installation of Vapor Retarders." Code of Federal Regulations: 24CFR3280.504. U.S. Government Printing Office via GPO Access from vww.hud.gov:80/offices/cpd/energvenviron/enerqv/lawsandregs/regs/subpartf/3280504. accessed on 3 Jun 03.

Council of American Building Officials. (1995). CABO: One and Two Family Dwelling Code. 1995 Edition. Fourth Printing. CABO; Falls Church VA; 350 p.

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Department of Energy. (2000). "Weather Resistive Bamers: How to select and install housewrap and other types of weather-resistive barriers." Technology Fact Sheet Series from the Office of Building Technology, State and Community Programs, Energy Efficiency and Renewable Energy, U.S. Department of Energy obtained from www.eere.energv.gov/buildings/documents/pdfe/28600.pdf. accessed on 28 May 03.

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Handegord, G. (1982). "Air Leakage, Ventilation, and Moisture Control in Buildings" in Moisture Migration in Buildings. ASTM STP 779; Philadelphia PA; 223-233.

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Holladay, M. and Vara, J. (2000). "More Housewrap Performance Tests." Journal of Light Constmction, 18(5), 13,16.

Housing and Urban Development (HUD). (2001). "3280.504 Condensation Control and Installation of Vapor Retarders." U.S. Department of Housing and Urban Development's Homes and Communities website at http://www.hud.gov:80/offices/cpd/energvenviron/energv/lawsandregs/regs/subpartf/3205 04.cfm. accessed on 3 Jun 03.

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Kumaran, M., Mitalas, G., and Bomberg, M. (1994). "Fundamentals of Transport and Storage of Moisture in Building Material and Componerrts" in Moisture Control in BuikJings. ASTTVI Manual Series: MNL 18; Philadelphia, PA; 3-17.

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Lstiburek, J. (2000). Builder's Guide to l\/1ixed Climates: Details for Design and Construction. The Tauton Press; Newton CT; 328 p.

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