NCARB Mini-Monographs and Liberty Building Forensics Group help keep you informed on the Hidden Risks of Green Buildings.
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1 NCARB MINI-MONOGRAPH NCARB’s latest initiative to inform and edu- cate can be found in our new “Mini- Monograph” articles, which will appear in each issue of Direct Connection. These arti- cles will take an in-depth look at topics of interest to architects, and provide NCARB Record holders with an efficient and eco- nomical way to earn one or two professional development (PDU) or continuing education (CEU) health, safety and welfare (HSW) cred- its through an on-line quiz. You’ll find our first Mini-Monograph, “The Hidden Risk of Green Building: Avoiding Moisture & Mold Problems,” in this issue. After reading the article, Record holders can earn one PDU by taking the online quiz for a fee of $35. To take the quiz, go to www.ncarb.org, log onto My NCARB Record, and then click on Mini-Monograph Quiz. You’ll be prompted to fill out the payment information. An online access code will be automatically e-mailed to you, which you can use to take the quiz at anytime. You’ll receive your results instantly, and if you pass the quiz you can immediately print your certificate of completion, and NCARB will report your continuing education credit to the AIA. Your payment covers the cost of administering the quiz and scoring. You even receive one free re-test should you not pass the first time. We hope you find our first Mini-Monograph that follows to be informative, provocative, and educational. If you’d like to learn more about mold and moisture, order a copy of NCARB’s monograph entitled, Mold and Moisture Prevention, or one of the other 20 titles from our monographs series. A com- plete list of NCARB monograph titles is avail- able on the back cover or by visiting the NCARB web site. DC NCARB Introduces Mini-Monographs: An easy way to stay informed and earn PDUs
Transcript
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NCARB’s latest initiative to inform and edu-
cate can be found in our new “Mini-
Monograph” articles, which will appear in
each issue of Direct Connection. These arti-
cles will take an in-depth look at topics of
interest to architects, and provide NCARB
Record holders with an efficient and eco-
nomical way to earn one or two professional
development (PDU) or continuing education
(CEU) health, safety and welfare (HSW) cred-
its through an on-line quiz.
You’ll find our first Mini-Monograph, “The
Hidden Risk of Green Building: Avoiding
Moisture & Mold Problems,” in this issue.
After reading the article, Record holders can
earn one PDU by taking the online quiz for a
fee of $35.
To take the quiz, go to www.ncarb.org, log
onto My NCARB Record, and then click on
Mini-Monograph Quiz. You’ll be prompted to
fill out the payment information. An online
access code will be automatically e-mailed
to you, which you can use to take the quiz at
anytime. You’ll receive your results instantly,
and if you pass the quiz you can immediately
print your certificate of completion, and
NCARB will report your continuing education
credit to the AIA. Your payment covers the
cost of administering the quiz and scoring.
You even receive one free re-test should you
not pass the first time.
We hope you find our first Mini-Monograph
that follows to be informative, provocative,
and educational. If you’d like to learn more
about mold and moisture, order a copy of
NCARB’s monograph entitled, Mold and
Moisture Prevention, or one of the other 20
titles from our monographs series. A com-
plete list of NCARB monograph titles is avail-
able on the back cover or by visiting the
NCARB web site. DC
NCARB Introduces Mini-Monographs: An easy way to stay informed and earn PDUs
Stewart Brand’s caution in 1994 about usingnew products is engaging and even quite contro-versial, since progress can only be made throughthe use of new products and innovativeapproaches. Yet Brand’s caution echoes whatforensic building consultants and building scien-tists have seen for decades; anything that departsfrom the “tried and true method” often fails.This finding is not surprising, since even tradi-tional building materials experience some per-centage of catastrophic failures from moistureand mold problems.
Brand’s caution seems particularly appropriatetoday with the proliferation of new products,many intended for LEED (Leadership in Energyand Environmental Design) certification.Although many of these products have beendeveloped within the last five years they areintended for use in buildings that should last for50+ years. Even a casual review of the literatureindicates that some of these products appear tohave minimal in-situ testing or performance ver-ification. Additionally, many of these productshave not been marketed in a manner suggestingcaution about regional or climatic restrictions in
their use. Finally, we suspect that there has beeneven less testing of the complex, interrelatedassemblies in which these products will be askedto co-exist for the next half century or more.
Yesterday’s seal of approval for new products was“It was developed by NASA.” Today the seal ofapproval is: it’s “organically produced,” LEEDcertified, “earth friendly,” or some variation ofthe above. Just as “NASA-developed” was noguarantee of success, neither is LEED-certifiedany assurance of no problems, especially thoseproblems related to moisture accumulation.
Although some indicators of a building’s per-formance (such as occupant comfort, energyusage, and odors) can be ignored, you can’t easilyignore water pouring through a wall assembly.We don’t believe that anyone would deem astructure “sustainable” if it cannot survive thefirst five years without a major renovationbecause of moisture problems.
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THE HIDDEN RISKS OF GREEN BUILDINGS: AVOIDING MOISTURE & MOLD PROBLEMS
Authors:J. David Odom, ASHRAE,Richard Scott, AIA/NCARB/LEED® AP & George H. DuBose, CGC Liberty Building Forensics Group, LLCOrlando, Florida
“Most new products are experiments and most experiments fail.” Quote from “How Buildings Learn: What Happens After They’re Built” by Stewart Brand (1994)
MONOGRAPHSERIES
NCARB
The opinions, beliefs, and viewpointsexpressed by the authors do not necessarilyreflect the opinions, beliefs, and viewpoints ofNCARB or serve as official policy of NCARB.
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It’s our belief that the moisture integrity of a building is one ofthe best report cards on the performance of its design and con-struction process and the correct use of materials.
After reviewing the designs of hundreds of new buildings overthe past 20 years and observing the failures in an equal num-ber of structures the authors have found the following consis-tent truths:
■ Building Commissioning—The current industryapproach to building commissioning (even the LEEDEnhanced Commissioning version EA Credit 3) isunlikely to prevent moisture and similar building failures in almost any climate, except for the most forgiving climate.
■ New Materials—The use of many new building prod-ucts often have the unintended consequence of perform-ing in unexpected ways, sometimes encouragingsignificant moisture accumulation and mold growth.Since wall and roof assemblies have historically beenhigh risk areas, it should be no surprise that theincreased use of new products in these areas can dramat-ically increase the overall potential of moisture problemswithin the envelope.
■ Increased Building Ventilation—The positive benefits ofincreased outside air ventilation for the occupant’shealth and comfort can oftentimes be outweighed by theincreased potential for moisture problems, some ofwhich have caused catastrophic failures in the past.Forensic engineers have strong evidence that buildingscan perform in unexpected and damaging ways whenadditional air is moved through them.
Through our evaluation of various LEED credit opportuni-ties for designers, we hope to establish the fact that a sustain-able building must be equally designed to prevent likelymoisture and mold problems. We believe that a building
attaining LEED certification is not necessarily a buildingwith a low potential for failure due to moisture intrusion.However, it is our belief that it is possible to combine LEEDcertification with the best practices for moisture and moldproblem avoidance – but it will require extra effort from botharchitects and mechanical engineers.
An important aspect to avoiding moisture problems in greenbuildings is the inclusion of the best practices from the water-proofing/HVAC (heating, ventilating, and air-conditioning)disciplines in combination with the LEED certification prin-ciples. It is unwise to assume that LEED certification hasautomatically incorporated those best practices. Green build-ing practices must always be subservient to best design prac-tices in areas such as exterior waterproofing, good humiditycontrol, and proper due diligence in selecting new construc-tion materials.
In order to facilitate the dual vision of an environmentally-sensitive building with a highly durable, well performing,moisture resistant building, we have compressed a significantamount of data into the following discussion. This discussionmoves from an overview of LEED® certification points withpotential moisture issues (shown in a table) to a moredetailed analysis of several specific LEED credits that we viewas examples of high risk. These are credits that align with theconsistent truths we listed above concerning building com-missioning, new materials, and ventilation issues.
The concerns raised in the following pages are not climati-cally or regionally specific, but are universal concerns for allbut the most forgiving climates. Forgiving climates wouldinclude those areas with very low rainfall, year-round moder-ate temperatures, and minimal humidity levels. Even in thoseclimates specific building types could be expected to exhibitproblems if best practices are not followed.
CONTINUING EDUCATIONUse the following learning objectives to focus your study while read-ing the semi-annual Direct Connection/ Professional Development(PDU) and AIA Continuing Education (CU) HSW credit article. Toreceive credit:
1. Go to the NCARB web site atwww.ncarb.org
2. Click on monographs3. Fill out the registration form and
payment information4. Take the quiz using your online access
number
LEARNING OBJECTIVESAfter reading this article, you should be able to:1. Comprehend how standard good practices for building design
require additional diligence due to the enhanced likelihood ofmoisture intrusion connected to building commissioning proto-col, ventilation, design, and novel building products.
2. Identify the specific LEED credits that increase the potential for moisture intrusion problems during sustainable building design.
3. Understand the contributions that good building envelope andmechanical design play in planning a sustainable buildingresistant to moisture problems.
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EA Prerequisite 2 andEA Credit 1
1. Increased thermal insulation changes wall sys-tem performance (dew point location) with pos-sible condensation in wrong location.
2. Modifying heating, ventilating, and air-condi-tioning (HVAC) control schemes alters equip-ment run times and impacts moisture control.
Increases in energy performance can reducemoisture control in buildings.
Energy & Atmosphere(EA) Prerequisite 1and EA Credit 3
1. The typical commissioning design review is notlikely to predict the potential for future mois-ture and mold problems.
2. The reviews normally do not incorporate ananalysis of the building envelope performance.
FundamentalCommissioning of theBuilding EnergySystems andEnhancedCommissioning
Enhanced commissioning addresses only themost forgiving climates.
Sustainable Sites (SS)Credit 7.2
Vegetated roofs have more moisture due to irriga-tion and constant hydrostatic head of water thantypical roofs, making it difficult to prevent waterintrusion and condensation problems. Moisturemigration & concentration between impermeablemembranes is a possibility.
Heat Island Effect:Roof
Option of installing a vegetated roof for at least50 percent of roof area.
MR Credits 1.3, 2.1,2.2, 3.1, and 3.2
1. Mold contamination is not often visible in theoccupied side of materials and is not generallyfound by air testing in a construction environ-ment. Destructive testing and evaluation maybe required.
2. Construction waste management plan may needto include section on handling moldy materials.
Inadvertent reuse of previously water damagedand/or mold contaminated materials presentsan increased risk. Construction workers at riskof handing mold contaminated materials.
Materials andResources (MR)Credits 1.1 and 1.2
1. Quality and performance of existing componentssuch as flashing, rainwater barriers, air barriers,need to be investigated and possibly tested.
2. Model both new and re-used component toidentify how each component will act towardsgood moisture control — this includes interac-tion with the HVAC system.
Building Reuse:Maintain 75 percentto 95 percent ofExisting Walls, Floors,& Roof
Moisture control performance of existing build-ing envelope components re-used under thiscredit.
EA Credit 5:Measurement &Verification
Any good energy management plan must be subservient to adequate moisture control.
Ongoing energy measurement andverification
Sacrificing adequate relative humidity control toreduce energy usage.
Overview of LEED Credits That Have Increased Potential for Moisture & Mold Problems
OVERVIEW OF LEED CREDITS THAT HAVE INCREASEDPOTENTIAL FOR MOISTURE & MOLD PROBLEMS The following is a summary of LEED Credits that, if not carefully considered, designed, and constructed, have the potential for creating moisture andmold problems. This summary also includes LEED Credits that can be enhanced to minimize the potential for moisture and mold problems:
LEED CREDITNUMBER DESCRIPTION ISSUE COMMENTS
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MR Credit 6 The mixture of synthetic materials with naturalmaterials in the building envelope can createincreased potential for moisture condensationand entrapment.
Rapidly RenewableMaterials
Use of rapidly renewable natural building materi-als and products without understanding theirproperties related to water (permeance, absorp-tion, etc.).
Increased ventilation air should never be addedwithout an overriding control of both pressuriza-tion and dehumidification.
Minimum Indoor AirQuality (IAQ)Performance, Outdoor Air DeliveryMonitoring, andIncreased Ventilation
Ventilation in many parts of the United Statesmust to be carefully designed to avoid moistureproblems .
EQ Credit 3.1 Construction sequencing needs to be reviewedand material protection measures understoodand enforced.
Construction IAQManagement Plan:During Construction
Typical construction sequencing does not alwaysallow for meeting credit objectives for protectionof materials from water damage.
EQ Credit 3.2 (and3.1)
Introducing required air for this credit in manygeographic areas can result in indoor moistureproblems.
Construction IAQManagement Plan:Before Occupancy
Pre-occupancy flush out.
EQ Credit 5 Local exhaust can result in local depressurizationand introduction of humid outside air into build-ing envelope. It can also result in inadvertent pol-lutant movement within a building.
Indoor Chemical &Pollutant SourceControl
Requires significant exhaust rates for sourcecontrol.
EQ Credit 6.2 If operable windows are installed, consider sen-sors and automatic overrides.
Controllability ofSystems: ThermalComfort
Providing operable windows can allow untreatedhumid air or rainwater to enter building.
Innovation in Design(ID) Credits 1.1-1.4
1. Probably unrealistic for the design and construc-tion team to understand the performance char-acteristics and limitation of new products andthe additional risks that their use might carry.
2. Particular concern about the introduction ofnew products into the highest moisture riskareas of the building (i.e., the envelope and theHVAC system) since in these areas there isadded risk.
Innovation in Design Recognizing the inherent increased risk of usingnew products that have less in-field experience.
LEED CREDITNUMBER DESCRIPTION ISSUE COMMENTS
Building commissioning (even the enhanced version of com-missioning in LEED EA Credit 3) is not likely to prevent cat-astrophic moisture and mold problems. Traditionalcommissioning fails to accomplish two primary requirementsin avoiding moisture problems:
1. The design review is not likely to be a “standard of care”technical peer review, but is more often a reviewintended to determine if the constructed building, oncebuilt, can be commissioned and if the design meets theOwner’s intent. In our experience the typical designreview will not predict the potential for moisture andmold problems. Without this prediction it cannot offerspecific solutions to avoid them.
2. These reviews are not required to incorporate an analysisof the building envelope’s performance—the acknowl-edged component that fails the most frequently and usu-ally the most dramatically.
What the building science industry has known for some timeis that moisture and mold problems are often very pre-dictable, even in the early design stage. However, for this
analysis to be successful the review team must be very savvyabout what combination of design choices create a high riskof causing problems and what other choices are lower risks.
Figure 3.1 shows an example of the predictability of moistureand mold problems in a hotel type building.
Some concepts that should be included in building commis-sioning to reduce the possibility of moisture and mold prob-lems include the following:
■ During the design phase a technical peer review of thedocument should identify issues which will likely bemajor cause of moisture and mold problems in the oper-ating building. This review may need to be accom-plished by someone other than the traditionalcommissioning agent since they may not have the requi-site skill set to conduct this type of analysis. It’s ouropinion that this review needs to specifically identifywhich building components and systems have a highpotential for moisture problems and offer alternativesolutions to the design team.
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FIGURE 3.1: Prediction
chart of the probability of
moisture and mold in a
hotel-type building with a
series of HVAC system
choices and an unforgiv-
ing wall system—i.e., a
misplaced vapor retarder
in conjunction with mois-
ture sources. Other com-
binations of decisions can
increase or decrease the
risk. (Note: This example
makes numerous assump-
tions such as there are no
significant rainwater leaks.
This prediction chart also
assumes that the outside
moisture conditions are
conducive to mold
growth.)
Intent of EA 1: Verify that the building’s energy related systems are installed and calibrated, and performaccording to the owner’s project requirements, basis of design, and construction documents.
Intent of EA 3: Begin the commissioning process early during the design process and execute additional activ-ities after systems performance verification is completed.
FUNDAMENTAL COMMISSIONING (EA PREREQUISITE 1)AND ENHANCED COMMISSIONING (EA CREDIT 3)
Continuous Toilet Exhaust
No Conditioned Make-Up Air Conditioned Make-Up Air
Ducted to Each RoomNot Ducted to Each Room
PTAC Unit FCUPTAC Unit FCU
Mold Probable in Room
Mold Probable in Room
Mold Possiblein Room
Mold Possiblein Room
Mold HighlyProbable in Wall
Mold HighlyProbable in Wall
Mold Probable in Wall
Mold Probable in Wall
PTAC Unit FCU
Mold UnlikelyIn Room
Mold UnlikelyIn Room
Mold Possiblein Wall
Mold Possiblein Wall
PTAC (Packaged Terminal Air Conditioning Unit) FCU (Fan Coil Unit)
■ The commissioning process needs to consider the inter-relationship of the building envelope and the HVACsystem. This area is often overlooked because it involvesthe dynamic interaction between two separate technol-ogy areas.
■ The building envelope needs to be commissioned in amanner that would avoid rainwater leaks, excessive airleakage, and condensation problems. In cases where theenvelope is commissioned, both individual envelopecomponents (like windows) should be tested as well asassemblies of multiple adjacent components. Testing
individual components does not address the connectionpoints and intersections between various envelope com-ponents where most of the failures occur. Assembly test-ing can include a mix of qualitative (Figure 3.2) andquantitative testing, such as ASTM tests.
■ Construction phase commissioning of envelope compo-nents may require adjustment of installation methodsbased on test results. Checklists should be developedthat allow for certification that such adjustments areimplemented (Figure 3.3).
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FIGURE 3.2 (left):Qualitative water testing
of window and stud wall
assembly after installation
of membrane water
proofing. Note spray rack
(red arrows) above and
to the side of window
that washes the wall
while the cavity side of
sheathing is checked
for leaks.
FIGURE 3.3 (right):Checklists for commis-
sioning of sliding glass
doors. These checklists
are completed by the
contractor. The checklists
may be modified after
installation and quantita-
tive testing of the first
several doors.
MATERIALS & RESOURCES AND OTHER CREDITS: USE OFNEW MATERIALS IN HIGH RISK LOCATIONS
Intent of these 14 Materials & Resources Credits: Reuse of existing building components, the managementof construction waste, materials reuse, amount of recycled content, the use of regional materials, the use of rap-idly renewable materials, and the use of certified wood.
New green materials can often meet requirements in severalLEED credits. For example, organic-based insulation materi-als can satisfy LEED Material & Resource Credit 6 as a rap-idly renewable material, Energy & Atmosphere Prerequisite 2and Credit 1 for energy performance, and IndoorEnvironmental Quality Credit 4.1 for low emitting materials.Many new materials and concepts can also fall under theInnovation & Design Process credit requirements for devel-oping new solutions, employing new technologies, or realiz-ing exemplary performance.
We believe that it is reasonable to assume that if we are rela-tively unfamiliar with a new material’s individual perform-ance then we probably know even less about the material’sinteraction with other adjacent components. Our ignoranceabout the performance of new materials should not be disre-garded because the manufacturer of these materials assures usthat the product is appropriate for LEED-certified buildings.The recognition of additional risk in the use of innovative
products (especially in the envelope and HVAC systems) bythe development team should demand a higher degree ofrigor in the evaluation of these products.
As previously mentioned, the interaction between the HVACsystem and the envelope creates an unusually high risk area.The impact of this condition is that any deficiency in eithersystem can cause dramatic building-wide moisture problems.
It may be only a slight overstatement to state that there is nowall system which a creative architect can envision that apoor HVAC system cannot destroy. Conversely, a very wellperforming HVAC system can often compensate for a mar-ginally designed (or constructed) building envelope to thepoint where many moisture problems may never be noticed.However, there is a point where even an exceptionally wellperforming HVAC system cannot compensate for a poorlydesigned wall system, especially a wall that allows rainwaterintrusion or is excessively leaky to air movement.
A simplification of the above concept can be stated as: ■ Bad Envelope Design + Bad HVAC Design =
Guaranteed Moisture Problems■ Good Envelope Design + Bad HVAC Design =
Likely Moisture Problems ■ Bad Envelope Design + Good HVAC Design =
Likely Moisture Problems■ Good Envelope Design + Good HVAC Design =
Likely Success
(Note: The term “Good Envelope Design” refers to thecorrect design and construction of the air barrier, vaporretarder, and thermal barrier. It does not refer to rainwaterintrusion issues since even minor rainwater entry past thewater resistive barrier can be problematic. “Good HVACDesign” refers to the proper building pressurization forthe specific climate, proper dehumidification, and properair distribution within a building)
Although new wall system products are often intended toprovide better thermal insulation, reduce air movementthrough the walls, or allow enhanced drying of the wallassembly (via vapor diffusion) they can also perform in unan-ticipated ways. These new products can dramatically changethe way moisture flows through wall and roof systems andthe potential for condensation within these cavities. The useof these new products mandate that the designer implementseveral additional steps to avoid problems:
1. Better understand the performance characteristics ofthese new products. This may require a more rigorousevaluation of these materials than is required with tradi-tional products. As with any product —but more so withnew products—the performance answers may not befound in the product data sheets, but may require experi-ments and mockups to determine their performance.
This type of evaluation may be beyond the scope andexpertise of the design team — but it should neverthelessbe implemented. In Figure 3.4 above, a new insulationmaterial (marketed for “green” buildings) was able tohold a considerable amount of water despite a data sheetthat indicated it was a non-absorptive product. The useof this material in wall cavities could create massive moldproblems if there is water leakage through the water resis-tive barrier since the normal wet-dry cycling will notlikely occur.
2. Analyze the vapor retarder, air barrier, and bulk waterretention properties to better understand where thematerial should be placed, if at all, within the wall sys-tem.
3. Model the wall systems for performance during the earlydesign stages to predict the potential for water vaportransmission through the wall assemblies and potential forcondensation to occur. Minimally, this modeling shouldpredict the dew point location and the vapor transmissionprofile during the most extreme season for the location.
4. Perform a three-dimensional analysis of rainwater barriergeometry, especially at complex joints and changes inplane.
All other standard good practices for wall system designshould continue to be followed whether new or traditionalproducts are used including: ■ The use of water resistive barriers as the first line of
defense, ■ Designing drainage planes to channel water down and
out of the envelope, ■ Installing secondary barriers for redundancy ■ Designing proper flashing and sealant joints.
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the amount of water
absorbed by a wall insula-
tion product. This experi-
ment demonstrates that
many products intended
for wall and roof assem-
blies can absorb huge
amounts of water in spite
of their data sheets
attesting to the opposite.
For decades there have been competing arguments within themechanical design community on whether to increase ordecrease the amount of outside air that is introduced intocommercial and institutional buildings. Although there aresound arguments on both sides of the debate, today’s empha-sis on increased building ventilation to achieve LEED creditshas given an added incentive to increase the amount of out-side air to buildings. The experience of many forensic build-ing experts (especially in the eastern half of the country) donot necessarily support the theory that adding more outsideair creates a better performing, more sustainable building—sometimes quite the opposite (Figure 3.5).
What is known about ventilation air is that in regions withambient high dew point conditions and elevated relativehumidity levels (which include much of the entire eastern halfof the country during portions of the year) there is a directcorrelation between the number of moisture problems andincreased rates of mechanical building ventilation. This canoccur for obvious reasons, such as the additional moisture loadthat is introduced into the building along with the outside air.However, more obscure reasons can also increase the risk ofadding outside air to a building. Unbalanced (or partially
depressurized) buildings can be the result of moving largeamounts of air around a building. When this condition occursmoisture problems become more prevalent. These unbalancedconditions happen when air is trying to flow from the supplyside of the air handler equipment to the return side but isrestricted by structural or architectural barriers.
Florida Solar Energy Center (FSEC) of Cocoa, Florida calledthis condition the “Smart Air Syndrome” concept—that air issupposed to be smart enough to get from one place toanother in spite of barriers. Additional ventilation air shouldalways be designed in conjunction with considering theimpact of the distribution of the ventilation air. This requiresidentifying parts of the building that could become depres-surized with respect to outside conditions, thus potentiallydrawing humid outside air into the envelope cavity or occu-pied spaces. (Note: Even in less humid climates an unbal-anced HVAC system can inadvertently transfer odors andairborne pollutants in unintended ways through a building.)This increased risk of moisture problems caused by greater airvolumes (and thus unbalanced areas of the building) isdepicted in the FSEC graphic below (Figure 3.6).
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FIGURE 3.5: Martin
County Courthouse,
Stuart, Florida. The HVAC
design produced high
rates of outside air venti-
lation but poor tempera-
ture and humidity control
which contributed to
mold and moisture prob-
lems, resulting in over
$10 million in renovation
costs for a 3-year old
building.
INCREASED VENTILATION (EQ CREDIT 2) Intent: Provide additional outdoor air ventilation to improve air quality for improved occupant comfort, wellbeing and productivity.
Source: 1996 Florida SolarEnergy Center (FSEC) Study.
FIGURE 3.6: FSEC
graphic on risk of building
failures related to building
complexity and intensity
of HVAC drivers (air vol-
umes and pressures).
Source: 1996 Florida Solar
Energy Center (FSEC)
Study.
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During construction there can be increased pollutant load ina building because of various factors: heavy particulate loadand the off gassing of formaldehyde and volatile organic com-pounds (VOC’s) from newly installed products. There arevarious methods of controlling this additional pollutant loadsuch as additional air filtration, the use of temporary air han-dlers for heating and cooling, and flushing out the buildingwith additional amounts of outside air.
As proposed by LEED Credit 3.2 building flush out can occureither late in the construction phase or after the building isoccupied. While the use of outside air to flush out the build-ing may reduce the concentration of off gassing it can alsoinadvertently cause moisture problems. Although the moistureproblems may be short term (decreasing after the flush out isfinished) the resultant mold problems could be long lasting.
The EQ Credits related to the Construction IAQManagement Plan allow for two separate approaches to build-ing flush out, one during construction and an alternative planafter occupancy. Both approaches involve a substantialamount of outside air volume—14,000 cubic feet (cfm) persquare foot (SF) of floor area. Whether this flush out occursrapidly over a several week period (during the late stages ofconstruction) or more slowly over several months (duringpost construction) moisture problems are likely to result inmany parts of the country during the summertime.
Increased building ventilation over the design amounts cancreate a range of problems such as inadequate sizing of the airfilters and an inability of the air conditioning equipment to
handle the increased moisture (or latent) load. While theLEED credit mandates a 60 percent RH maximum level dur-ing this flush out period this requirement may not be feasiblewith the building’s equipment. Since final building finishesshould be in place prior to flush out (otherwise there are nomaterials to off gas) it makes the entire building susceptibleto mold growth problems. If building flush out occurs afteroccupancy then even the furnishings are susceptible to moisture problems.
In a typical 100,000 square foot building the amount of out-door air required to meet the flush out portion of this creditis 1,400,000,000 cubic feet. This amount of air volume inthe eastern portion of the country during the humid summermonths can be equivalent to over 200,000 gallons of addi-tional moisture introduced into the building. This moisture isin addition to the normal moisture load from constructionactivities, cleaning liquids, or construction-related moisturefrom curing concrete, paint drying, etc.
One of the additional risks with conducting building flushout (especially in an occupied building) is that it is usuallydone in the evening when the heat load (sensible) is the low-est and the moisture load (latent) is the highest. This canresult in even greater relative humidity levels in the buildingbecause the unfavorable ratio of sensible to latent load caneither cause overcooling of the building (resulting in flashcondensation). The additional likelihood that the HVAC sys-tem might still be unbalanced at the time of the flush outincreases the potential for moisture problems as the result ofthis process.
CONSTRUCTION IAQ MANAGEMENT PLAN DURINGCONSTRUCTION AND BEFORE OCCUPANCY (EQ CREDITS 3.1 AND 3.2)
Intent: Reduce indoor air quality (IAQ) problems resulting from the construction/renovation process in orderto help sustain the comfort and well-being of construction workers and building occupants.
FSEC’s research has demonstrated the relationship betweenbuilding complexity (architectural and structural complexity),the intensity of the HVAC drivers (air volumes and pres-sures), and the risk of building failures. The solution is not tobuild simpler, less ventilated buildings but it is to insure thatthe ventilation air is effectively delivered to the space. Thismeans that ventilation must be distributed so that it not onlyreaches the desired breathing zone but does so in a mannerthat does not adversely affect the building.
The HVAC system that introduces ventilation air must alsodo so in a manner that properly dehumidifies the air. The“golden rule” of moisture control is that under no circum-stances should adequate dehumidification be sacrificed forincreased ventilation. In many regions of the country duringsummertime conditions the moisture load contributed by theoutside air can exceed the amount of moisture that the air-conditioning system can effectively remove.
The solution is to address these risk factors in several ways:
■ Insure the correct distribution of air flows within build-ings (to avoid pressure imbalances). This can usually beaccurately predicted during design.
■ Increase the verification of HVAC system performanceby adding additional elements to the building startupand commissioning programs. This post-constructionverification includes detailed pressure mapping of thebuilding to confirm proper air distribution and usingtemperature and relative humidity (RH) data-loggers toconfirm conditions during the first year’s operation. Thispressure mapping and data logging needs to also includethe building cavities—areas that are often ignored.Many of these elements are frequently absent in today’sstandard HVAC system startup and building commis-sioning programs.
What experience demonstrates is that increased amounts ofoutside air can be safely added to a building if the knowncauses of increased risk (such as proper air distribution) areaddressed during design and verified after construction.
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Depending on the climate where the building is located itmay be important to utilize different types of ventilationapproaches to control indoor air quality degradation andindoor chemical and pollutant source control. In climateswith outdoor air conditions that carry large summer moistureloads (which includes much of the eastern portion of thecountry), ventilation approaches should include a combina-tion of exhaust and make up air to achieve the pressure differ-entials required by the credit.
This credit requires a pressure differential of 5 Pascal’s (Pa)between the area with the chemical or pollutant source andadjacent areas. The recommended approach is to exhaust thespace with the chemical or pollutant source to a point that isat least 5 Pa negative when compared to adjacent areas and aminimum of .50 cfm per SF. If this recommendation is incor-rectly applied its result can create depressurization of theentire building (or portions of the building).
The inherent risks associated with increased building exhaustas recommended in this LEED credit are numerous:
■ It increases the importance of a very accurate test andbalance process to insure that adjacent building areas arenot accidentally depressurized (including wall and ceil-ing cavities).
■ The suggested pressure differentials (5 Pa) are signifi-cantly more precise than the average test and balancefirm can measure, likely leading to errors.
■ Since the suggested exhaust rates and pressure differen-tials are minimum figures there might be a tendency forsome practitioners to vastly exceed these amounts (underthe concept that “more is better”) which could result inan even increased potential for uncontrolled air flowsand moisture problems.
It has been the experience of many practitioners in the fieldof forensic building science that achieving negative pressureconditions in parts of a building, while maintaining overallpositive building pressures elsewhere is an extremely delicatebalance to achieve.
INDOOR CHEMICAL & POLLUTANT SOURCECONTROL (EQ CREDIT 5)
Intent: Minimize exposure of the building occupants to potentially hazardous particulates and chemical pollutants.
The green design movement is transforming the design andconstruction marketplace like no other innovation in the life-time of most designers. Green design has brought to theforefront of the design and construction community a holisticview of how to design, build, and operate higher performingbuildings. As such, the noble goals espoused by sustainabledevelopment and green buildings are certainly worth aggres-sively pursuing — but it must be done with significant care,especially in the areas of high risk for moisture and moldproblems. It seems that some of the “best practices” and“lessons learned” in other fields are not being applied in aprecise enough manner when it involves green construction,at least as that applies to moisture control.
To summarize our recommendations we believe that the fol-lowing should occur in an effort to enhance green designs:■ A technical peer review of the design should be imple-
mented that attempts to predict the building perform-ance with the new materials and products. At aminimum this review would focus on the HVAC andbuilding envelope systems that are most exposed tomoisture-related failures. This should provide a moreclimatologically and regionally accurate green design.
■ The design team must be confident that they haveincorporated the institutional knowledge already knownin the fields of humidity control, waterproofing andbuilding envelope performance. Processes that havealready lost favor in the indoor environment field, suchas “building flush out,” should not now be incorporatedinto green construction as “best practices.” These
processes have historically shown little benefit and havedemonstrated high cost, high risk, or both.
■ The acceptance of new products with specific “green”benefits should be especially scrutinized. Our experienceis that gaining performance in one area often means sac-rificing performance in another area. If the area whereperformance is sacrificed is a critical parameter (such asthe water absorption qualities of wall insulation) thenthe risk may be too great, no matter what the benefit is.We are not sure if it’s realistic for a design team to makeall of these required assessments, but without it buildingfailure seems more probable.
As Fortune magazine once stated: “If mind-boggling change is the only constant, focusing on theavoidance of major blunders yields better results than the single-minded pursuit of the big win.”
Liberty Building Forensics Group is a firm that specializes inforensic building investigations and repairs of building failures,moisture & mold investigations and repairs, waterintrusion/building envelope assessments and repairs, expert wit-ness/ litigation support, and building commissioning/HVAC per-formance evaluations. Their staff led the investigations andlitigation support of some of the largest building failures in thecountry including the $60 million moisture problems at a luxuryresort in Honolulu, HI, and the $20 million Martin CountyCourthouse in Stuart, FL. They have performed technical peerreviews on over $2 billion in new construction since 1995. Theycan be reached at www.libertybuilding.com or at 407-703-1300in Orlando, FL.
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