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BREATHING ROOM 1 Breathing Room: Solutions for Attawapiskat Susan Reid Thompson Rivers University Architectural and Engineering Technology 2012
BREATHING ROOM 1
Breathing Room: Solutions for Attawapiskat
Susan Reid
Thompson Rivers University
Architectural and Engineering Technology
2012
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Abstract
Breathing Room: Solutions for Attawapiskat is an examination of the problem of mould
growth in conventionally stud-framed residential buildings in Attawapiskat, Ontario; it proposes
solutions using resistant wood-based wall assemblies in construction. The background research
is from primary and secondary data sources, and forms the basis of selection for the suggested
solution wall assemblies.
A practical experiment of six weeks duration was used to test a standard 2” x 6” stud-
framed wall, a CLT (cross-laminated timber) wall, SIPs (structural insulated panel) wall, and a
NDW (wood- fibre) panel wall. These walls were assembled into a small shed measuring
approximately 4’x4’x4’, mounted on an insulated 2” x 6” stud-framed base, and covered with an
insulated 2” x 6” stud-framed roof. The roof was finished with asphalt shingles, and the exterior
walls were covered in aluminum siding. A lamp and a hot-water vaporizer were mounted inside
the shed to provide heat and humidity, and both were cycled on/off at 8-12 hour periods. The
experiment subjected the selected walls to extremes of humidity with adequate warmth in order
to accelerate mould growth.
The final results show that both the NDW wall and the CLT wall had similarly low
mould growth by area, and low concentrations of mould where seen. However, although the
CLT wall showed most of its mould growth within the first three weeks of testing, the NDW wall
did not develop growth until after the three week inspection. Because of this resistance to initial
growth, the NDW wall is recommended for future residential construction in Attawapiskat, and
other comparable communities.
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Table of Contents
Abstract ........................................................................................................................................... 2
List of Figures ................................................................................................................................. 4
Breathing Room: Solutions for Attawapiskat ................................................................................. 5
Literature Review........................................................................................................................ 6
Mould Growth: Conditions and Problems .................................................................................. 6
Part One: Attawapiskat ............................................................................................................... 8
Part Two: Experimental Solutions .............................................................................................. 9
Results ....................................................................................................................................... 11
Analysis and Discussion: Part One ........................................................................................... 14
Analysis and Discussion: Part Two .............................................................................................. 24
Weather Conditions .................................................................................................................. 24
Air Leakage ............................................................................................................................... 25
Interior Conditions .................................................................................................................... 25
Conclusions ................................................................................................................................... 26
Recommendations for Attawapiskat ............................................................................................. 28
Glossary ........................................................................................................................................ 29
References ..................................................................................................................................... 30
Appendix A ................................................................................................................................... 34
Building Details ........................................................................................................................ 34
Appendix B ................................................................................................................................... 39
Photos of Mould Growth after 3 weeks .................................................................................... 39
Photos of Mould Growth at 6 Weeks with Analysed Patterns.................................................. 41
Appendix C ................................................................................................................................... 44
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List of Figures
Figure 1: Conditions for Mould Growth (Black, 2006) .................................................................. 7
Figure 2: Mold Damage to Indoor Relative Humidity (Nofal, 1999) ............................................. 7
Figure 3: Heat and Humidity over Testing Period ........................................................................ 12
Figure 4: Mould Growth by Area ................................................................................................. 13
Figure 5: Mould Growth by Intensity ........................................................................................... 13
Figure 6: Movement of water through the stud-framed wall, source (May, 2005) ...................... 20
Figure 7: Movement of water through the breathing frame, source (May, 2005) ........................ 21
Figure 8: Cross-section of standard wall ...................................................................................... 34
Figure 9: Cross-section of SIPs wall ............................................................................................. 35
Figure 10: Cross-section of CLT Wall.......................................................................................... 36
Figure 11: Cross-section of NDW wall ........................................................................................ 37
Figure 12: Section of Experimental Shed ..................................................................................... 38
Figure 13: SIPs to CLT corner ...................................................................................................... 39
Figure 14: Bottom of SIPs wall .................................................................................................... 39
Figure 15: Bottom of Stud-Stud-framed Wall .............................................................................. 40
Figure 16: Stud-Frame to NDW corner ........................................................................................ 40
Figure 17: 2” x 6” Stud-framed Wall and Mould Growth ............................................................ 41
Figure 18: SIPs Wall and Mould growth ...................................................................................... 42
Figure 19: CLT Wall and Mould Growth ..................................................................................... 42
Figure 20: NDW wall and Mould Growth .................................................................................... 43
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Breathing Room: Solutions for Attawapiskat
This intent of this research is to find a technical answer for the common problem of
residential mould growth such as occurred in Attawapiskat. Currently, the ubiquitous timber-
stud-framed home, which serves well enough for urban Canada, does not succeed in this area and
similarly remote and northern locations. The failure in building performance in these areas is
due to a combination of circumstances: lifestyle differences dictated by culture and location, and
a lack of established infrastructure for skilled construction workers, supplies, and maintenance
capability (Humphreys, 2006). When the building performance failure is accompanied by the
growth of mould, the resulting presence of spores and micro-toxins lead to increased asthma
symptoms and other respiratory afflictions, depending on individual sensitivities. (Health
Canada, 2007)
Facing widespread and systemic challenges inherent in aboriginal building issues in
Canada, this research has limited scope, focusing on finding a technical solution to resisting
mould growth in the building frame. A small shed, composed of three alternate wall assemblies
and one conventionally stud-framed timber wall, has been subjected to high humidity, over 70%
RH(relative humidity), conditions and maintained at a temperature over 20oC. It has been
finished externally in a typical residential manner, and sealed against air-leaks on the interior.
Although it is hoped that the finishing of the shed and the interior conditions of construction and
warmth will closely approximate a real-life situation, we recognize the limitations of a study of
this size, and have limited the defining condition to high relative humidity.
The other parameter is that all proposed solutions are limited to wood-based assemblies
that are commercially available in British Columbia. Although Attawapiskat is located in
Ontario, its problems are considered to be common to many areas of Canada, including British
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Columbia. It is not within the scope of this project to directly test materials from Ontario in a
Northern Ontario climate, and so conditions and materials must be approximate. By limiting the
research to materials and climate in British Columbia, general conclusions relevant to
Attawapiskat can be drawn, and specific conclusions can be related to the Government of British
Columbia’s Wood First Initiative, BC First Nation Economic Development Action Plan, and to
housing issues in regional aboriginal communities.
In doing so, not only may we find reasonable suggestions for future building materials for
our defined problem, but we may also be able to present an elegant solution that addresses
several peripheral conditions. There may be a better way to build in isolated and, often, largely
aboriginal communities; it is only fitting that in approaching this particular Canadian challenge, a
representative Canadian solution should prevail.
Literature Review
Mould Growth: Conditions and Problems
Mould growth inside a building, although it does not compromise the structural
performance of the building, can cause allergic reactions and advance existing respiratory
problems in the occupants by spreading spores and micro-toxins (Dales RE, 2006). The number
of spores inside can be increased by daily living, including cleaning activities such as vacuuming
(Black, 2006). This is not a specific problem segregated in remote locations; over 270 different
strains of mould have been identified as present in Canadian homes, regardless of area (Health
Canada, 2007). By finding reasonable solutions to particular problems facing Atttawapiskat,
these solutions may be applied with confidence in other areas of the country facing similar
issues.
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In order to understand this problem, a basic understanding is needed of conditions under
which mould develops. Mould spores are introduced into the home from outside by occupant
traffic, pets, stored firewood, and ventilation. Once inside, mould needs three conditions:
Nutrients, Moisture, and Correct Temperature.
Figure 1: Conditions for Mould Growth (Black, 2006)
Figure 2: Mold Damage to Indoor Relative Humidity (Nofal, 1999)
Stud-framed houses provide ample nutrients if the spores gain access through holes and
tears to vapour barriers in the interior of the home, and external damage to walls. A temperature
0.25 L/m2
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ranging between 20oC and 35oC provides optimal warmth, and a combination of high humidity
and low ventilation will supply the necessary moisture (Health Canada, 2007).
The above graph in figure 2 illustrates a dramatic increase in mould growth when relative
humidity exceeds 35%; noticeably, it is seen near the bottom of the wall. Other studies have
suggested that visible mould growth needed a RH (relative humidity) of over 80%, regardless of
temperature, or even 100% for results. It was proposed that while high humidity alone would
produce mould growth after several months, growth was accelerated into a period of weeks when
exposed surfaces experienced wetting (Black, 2006). From this, it can be summarized that an
indoor environment that is exposed to larger sources of mould spores (e.g. damp firewood
storage or pet traffic), is heated continually above 20oC, and produces large volumes of humidity
through living activities (e.g. larger number of occupants, cooking) with little ventilation to allow
dissipation will encourage conditions for visible mould growth. Any pre-existing problems (e.g.
construction with damp wood), damage to the building envelope, esp. the inside vapour barrier,
and lack of maintenance during the lifetime of the building will almost guarantee the appearance
of mould.
Method
Part One: Attawapiskat
Attawapiskat is a Cree First Nation with less than 2000 members living on a reserve near
James Bay, at the mouth of the Attawapiskat River. It is only accessible by a winter road from
January through March; otherwise all traffic in and out of the reserve is by air. Its situation is
fairly representative of other small, remote Aboriginal communities in this area and throughout
northern Canada, and as circumstances from one to another are common, it can be assumed that
the problems experienced will also be shared.
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In order to study the problem of mould growth in Attawapiskat, certain factors pertaining
to the problem of residential mould growth were examined.
1. General causes of mould growth and specifically how it grows in the building frame
2. Cultural and geographic features of life in Attawapiskat that specifically contribute to
mould growth in the building frame
3. Identifying key construction needs of this area and wall assembly types meeting these
needs
4. Identifying key characteristics of construction materials able to control causes of
mould and wall assembly materials with these characteristics
Primary and secondary sources were reviewed regarding mould growth, building materials, and
life in Attawapiskat. As a result of this study, three walls were chosen as likely solutions to this
building issue. A practical experiment was constructed with the walls-CLT, SIPs, and wood
fibre, in addition to a standard 2” x 6” stud-framed wall- over a period of six weeks in order to
test their resistance to mould growth.
Part Two: Experimental Solutions
Objective
The objective of the experiment was to simulate extreme indoor humidity and natural
environmental conditions reasonable near those of Attawapiskat during warmer months to test
mould-growth resistance of four unique wall assemblies.
Building Construction Details
The construction diagrams can be found in the appendices. A small experimental shed
was built using four complete wall assemblies cut to 4’x4’ size. The walls tested were a 2” x 6”
stud-framed wall (fig.20) as a control, a CLT (cross-laminated timber) wall (fig.21), a SIPs
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(structural insulated panel) wall (fig.22), and a NDW wall (fig.23). The shed was mounted on an
insulated wood-frame base, and covered with a similarly constructed roof covered in asphalt
shingle. Each wall had two nails hammered into it in the middle section to approximate
predicted damage that would normally occur during occupant use. A humidifier was installed to
produce water vapour, and a lamp with a 100W incandescent bulb was used for heat. After ten
days, the humidifier was replaced by a vaporizer. An aluminum duct was installed at the top of
the shed to house the temperature/humidity sensor and to provide access to a feed hose leading to
the vaporizer. A hole was cut above this area in the roof, under the shingles, in order to add
water to the vaporizer, and to take sensor readings with minimal disturbance to the interior.
Data Compilation
Inside and outside temperature and relative humidity was recorded each day;
approximately around 8:00 am and again at 4:00 pm. Water was added at these times, and the
light was switched on/off depending on the temperature recorded.
The interior of the shed was routinely checked for the first ten days of operation and no
mould growth was seen, although some light condensation was noticed. At ten days of
operation, the cool-air humidifier was removed, and replaced with a hot-water heating vaporizer.
On November 5, 2012, at three weeks of operation, the interior of the shed was inspected in
order to replace the light bulb and secure the vaporizer to the floor. Heavy condensation was
present, and substantial surface wetting was noticed. Large areas of mould growth were seen on
the floor. All walls, excepting the NDW wall, had visible mould growth, as well. This was
documented with casual photos and video. No analysis of the data was done at that time.
On November 24, 2012, the vaporizer and lamp were removed from the shed, and a series
of staged photos were taken of each wall. These photos were taken from the shed interior, and
BREATHING ROOM 11
each wall was photographed from 6 positions which were as nearly identical as possible for each
side. Gaps in the photography are consistent for each wall, and do not represent areas of
substantial, if any, mould growth on the walls. Inadequacies in the photography that reduce
precision in measurement, should not affect the overall accuracy of comparison.
Data Analysis
Heat and humidity for outside conditions and the shed interior were recorded
over the six week period and the results were graphed with avera ges and medians.
Each photo was opened in AutoCAD software (Figures 17-20, Appendix B), and scaled
to the correct size as indicated by the tape measure in each. The six photos for each wall (see
previous note) were visually point matched by wall feature and tape measure positioning. Each
composite image was then opened in ImageJ, a scientific image processing software, and the
areas of mould growth were highlighted. These areas were compared by pixel to the total area of
analyzed photo and the results recorded. The photos sizes were not identical, and any difference
in size is reflected in number of pixels per image. As the growth represented by pixel area is
expressed as a percentage of the total area analyzed, conclusions based on percentage can be
considered valid. Charts (Appendix B) were generated to represent the amount of mould growth
on each wall as a percentage of total area and to show the intensity of that mould growth in terms
of average size of connected particle by pixels.
Results
Heat and Humidity
During the testing period, outside temperature ranged from a low of 1oC up to a high of
18oC, averaging at 7.5oC. The outside humidity ranged from 36% up to 91%, averaging at 62%.
Inside the shed, temperatures fell as low as 7oC during a period of two days and rose as high as
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50oC during one afternoon. However, these were anomalies, and the overall average
temperature, 22.6oC, was close to the median of 22oC. Humidity ranged from a low of 42%
during the first week, to 81% after the hot-water vaporizer was introduced. The average was
76%, close to the median of 77% relative humidity.
Figure 3: Heat and Humidity over Testing Period
The outside temperatures did not appear to have a significant effect on inside
temperatures. This is believed to be due to heat generated by the light bulb in the first ten days,
and the insulation of the walls, roof, and floor, and later, because of the high temperatures
maintained by the water-heating vaporizer. As well, outside humidity did not appear to have any
noticeable effect on the inside humidity. The most significant factor for the inside humidity was
the introduction of the hot-water vaporizer which was able to maintain higher, and a more steady
level of relative humidity than the cool-water humidifier.
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Mould Growth
It is noted that when the mould growth was seen after three weeks, there appeared to be
substantial surface wetting inside the shed on the floor and all walls. The wetting is believed to
be partly from spills from the unsecured vaporizer during filling, and from the heavy
condensation produced by the vaporizer. The other observation noted is that the NDW wall did
not develop mould growth until after the three week inspection.
Figure 4: Mould Growth: Area of Mould as a Percentage of Wall Area
Figure 5: Mould Growth Intensity: pixel cluster size per area of mould growth
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Wood Fibre Wall CLT Wall 2x6 Framed Wall SIPs Wall
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At the end of the testing period, the NDW wall had both the lowest percentage of
coverage at 0.82% and the lightest coverage as represented by cluster size of mould areas. The
CLT wall was slightly higher, but comparable in both area coverage and intensity of growth.
The real differences were seen with the 2” x 6” stud-framed wall and the SIPs wall. In area
coverage, the SIPs wall was double that of the 2” x 6” stud-framed wall, and triple the CLT and
NDW walls. In heaviness of mould growth, however, the 2” x 6” stud-framed wall showed the
greatest intensity of mould growth, over double that of the comparatively light growth shown on
the CLT and NDW walls and over 80% higher than the SIPs wall.
Analysis and Discussion: Part One
Attawapiskat Case Study: Conditions and Problems
For Attawapiskat, and for similar remote reserves, it can be seen that the conditions optimal
for indoor mould growth are the norm and that as a result, serious problems from this condition
are more likely to be seen. Itemized, these conditions are (Humphreys, 2006):
1. Pre-existing problems due to inadequate construction
a. Materials stored on-site, leading to damage over time, e.g. torn poly sheets used
as vapour barriers allow moisture and mold spores to access the building frame
b. Wood materials not kept dry, construction with wet materials introduce moisture
into the building frame; vapour and moisture barriers do not allow diffusion
c. Lack of skilled labour in area, hurried construction with imported trades people
can lead to the previously noted problems, as well as improperly sealed building
envelopes
d. Construction not meeting the National Building Code minimum standards
2. Lack of adequate maintenance to the building
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a. Necessary knowledge lacking in occupants to do repairs
b. Limited knowledge resources available in area for maintenance
c. Difficulty in obtaining necessary equipment and supplies, and prohibitive expense
3. Problems with humidity due to occupant use
a. Higher number of occupants per dwelling unit on average compared to urban
areas
b. Longer period of cold weather with closed windows
c. Preparing game inside the home and boiling as a primary cooking method
d. Storage of firewood, leading to moisture given off by wet wood
e. Laundry left to dry inside the home
f. Inadequate or non-functioning mechanical ventilation
4. High concentrations of available mould spores indoors through daily activities
a. High occupancy leading to continual introduction of spores from vegetation,
animal waste throughout the day
b. Storage of firewood as a source of mould spores
As well, poor construction cannot be overemphasized as a cause of mould growth; Chief
Theresa Spence reports:
(Residential) units were built using untreated wood for foundation materials, which was prone to
mould, rot and collapse, vinyl siding (prone to breakage in extreme climates), and generally very
cheap construction.
It should be noted that the housing was built in 1985 to the Indian on Reserve building
code, and not to the National Building Code. In addition, because the houses were built without
accommodation for building services, adding electricity and plumbing later caused structural
BREATHING ROOM 16
damage to the homes and reduced available living space, accentuating already crowded
conditions. Due to poor design and installation, the sewage lines often backup and flood
basements, spurring the growth of mould spores (Spence, 2011).
The building design itself, imported from southern Canada, is often at odds with the
geographic and climate conditions in which it is built. Large differences between outdoor and
indoor temperatures during winter can produce condensation on the surfaces and interior of walls
(Said, 2006); this “wetting” action activates mould spores quickly (Black, 2006).
Maintenance, even of an adequately constructed home can be difficult in these areas.
Experts from southern Canada are normally flown in temporarily and infrequently to manage
projects; there is little in the way of community or business infrastructure to provide the “after-
market” know-how. The remoteness of location poses its own set of challenges: "We don't have
a Pro Hardware store…the closest place we can order [materials from] is Moosonee," (220 km
south of Attawapiskat by air) "We still have to bring those in by air, and it's not cheap," (Stastna,
2011).
Occupant use can increase the numbers of indoor mould spores, and produce the high
humidity and moisture on surfaces (“wetting” conditions) needed to initiate active spore growth.
Often wood-burning appliances are used. As the firewood may be stored nearby, radiant heat
from the appliances can activate spores in the wood. Preparing game, cooking by boiling,
washing and drying clothes inside, all contribute to inside humidity. Air circulation and natural
ventilation can be limited during several months due to continuously closed windows. As
overcrowding is commonplace, all of these factors can be considered to be increased. (Said,
2006)
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Defining the Solution
In order to determine a reasonable solution to the problem of mould, the elements
underlying the problem must be identified in terms of the building frame, and specifically in
regard to the composition of the walls in the frame. The solution is not concerned with suitable
design, but with improved construction and maintenance of the building, and should allow for
occupant use of the building that contributes to the presence of mould and high humidity.
Difficulties with construction can be minimized by using a wall system that resists
damage on the construction site, or can be quickly put into place once it arrives on site. Ideally,
it should be simple and fast for less-skilled workers to assemble with supervision, if a skilled
workforce is not available locally. Hiring and training locally is less costly for the construction
company, less demanding logistically, and provides additional income to the community.
For ongoing maintenance, a solution wall that is resilient and/or easily repaired will need
less maintenance and be more likely to be maintained by the occupants. This self-sufficiency for
maintenance should extend to resisting immediate conditions of high humidity through its own
material performance, rather than through reliance on mechanical services. As the occupant use
of the building is fundamental in creating these high-humidity conditions, any wall assembly
within the given parameters will be suitable for discussion.
In this report, three walls are evaluated for suitability:
1. NDW (Naturally Different wood-fibre) wall panel
2. CLT (cross-laminated timber) wall panel
3. SIPs (structural insulated panel) wall
All three walls are wood-based and commercially available in British Columbia. Because
they are pre-constructed panel walls, each allows ease and speed of installation and maintenance.
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The NDW wall and the cross-laminated timber wall can each be considered “breathing walls”,
while the structural insulated panel shares some of these characteristics.
Solution Elements
Construction with Panel Walls
Inherently, panel walls provide ease and speed of installation on-site. As they are
manufactured to order specifications, quality control is ensured and costs can be better
controlled. The panels are complete and do not require additional construction before use; they
can be erected in place upon delivery. Eliminating or reducing storage time also reduces the
possibility of damage to materials, especially by water. In conventional construction, walls that
are erected with wood that is less than completely dry will introduce moisture into the interior of
the building frame, and later provide conditions for mould growth. And finally, workers with
minimal training can successfully construct a residential building quickly with experienced
supervision and using basic construction tools. For a remote area where transportation costs are
high for construction materials moved by barge, panel walls can offer long term savings by
consistent levels of quality control and reduction in waste.
Maintenance with Panel Walls
Maintenance can be defined by any actions the occupants must take to ensure the
continuing function of the building in general, and the wall in particular. Maintenance for a wall
susceptible to mould would include keeping it dry and avoiding or repairing breaches to moisture
barriers. When the health of the wall is dependent on working mechanical systems, more
variables can increase barriers to successful maintenance. A panel wall that will perform well
against moisture, and therefore mould growth without need of mechanical aid will have a distinct
advantage over conventionally stud-framed walls which depend upon the continuing integrity of
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the inside vapour barrier to repel moisture away from the wall interior. This dependence
requires a fully functioning mechanical ventilation system to be successful. If the wall assembly
chosen has the ability to minimize as many variables, and therefore impediments to maintenance,
it will have a greater chance of contributing to the long-term building performance.
In this case, a panel wall which is able to process large volumes of water vapour will
have the greatest chance of success for resisting mould growth. The “breathing wall” is an
example of a particular assembly that, by its inherent characteristics, is able to contribute to its
own maintenance by its ability to process water vapour.
The Breathing Wall as a Panel Option
Any wall can be considered in terms of its vapour permeability- how fast vapour will
travel through a material, its hygroscopic ability-how water vapour is managed by cellular
absorption and release, and capillarity- how liquid is managed by absorption and release. In the
standard 2” x 6” stud-framed wall used in Canadian construction, there is a vapour barrier behind
the gypsum wall board on the interior face of the wall, and mineral wool insulation inside the
wall. The wall’s performance hinges upon the vapour barrier remaining intact and the initial
construction using wood that is completely dry. Unfortunately, at the time of construction, wood
can get wet on site during storage, and vapour barriers can be damaged by work done by trades
people. Once in use, a well-meaning resident can puncture the barrier by using large nails to
hang pictures, or by DIY repairs. The following diagram illustrates the resulting action of
moisture that promotes mould growth (May, 2005).
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Figure 6: Movement of water through the stud-framed wall, source (May, 2005)
Typically, moisture will move from an area of high vapour pressure to a low pressure
area: from high humidity inside toward the outside (Acker, 1998). If the vapour barrier inside
has been breached, any moisture that moves past it into the building frame will not return to the
interior due resistance by higher vapour pressure. Once in the frame, moisture will not dissipate
through the outside plywood building sheathing; on average, the resistance of plywood to
moisture is 100 times that of mineral wool insulation. However, as the insulation does not have
the hygroscopic ability to absorb moisture, it will, through vapour permeability, enable the
trapped moisture to diffuse into the timber frame where it is available for the development of
mould (May, 2005).
On the other hand, a breathing wall will capitalize on its natural abilities to create an
environment in which water can move freely from inside to outside faces. This dynamic
condition, because it does not allow the water to collect at any point, will discourage spores from
developing into mould. The following figure illustrates this movement of vapour through the
breathing frame.
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Figure 7: Movement of water through the breathing frame, source (May, 2005)
This illustration (Fig.6) shows OSB (oriented strand board) on the inside face of the wall.
Both OSB and plywood have higher resistance to moisture than GWB (gypsum wall board)
commonly used in residential construction; plywood’s moisture resistance is 80 times greater
than GWB and has superior performance longevity and resistance to mould growth under
prolonged conditions of high humidity. Natural fibre insulation in the building frame will
provide hygroscopic absorption of moisture, avoiding pooling of water by gravity, and vapour
permeability. When a wood fibre rigid insulation board is provided on the exterior for sheathing,
water vapour has the avenue to continue moving out of the frame. Provided all exterior finishes,
such as siding or brick work are attached with an air barrier, moisture will not be trapped in the
frame (May, 2005).
The Breathing Panel Solution
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If it is possible to combine the moisture handling characteristics that define a breathing
wall with the construction suitability of the panel wall, a reasonable solution may be proposed
for housing in Attawapiskat.
Comparisons of Panel Walls
This report evaluates three panel walls for their appropriateness as residential building
solutions for Attawapiskat. For initial construction, all three walls offer similar benefits for ease
of construction, and level of achievable building quality directly related to comparable
manufacturing controls and installation requirements. The second area of evaluation must be to
compare how each wall contributes to its own maintenance over the lifetime of the building. As
the focus of this report is mould-resistance, maintenance in this context will refer to how each
wall can be expected to behave under the particular conditions expected in Attawapiskat, or other
related community.
Types of Panel Walls
The NDW wall is a manufactured stud wall where the spaces between the studs are
insulated with wood fibre insulation, and covered with structural wood fibre insulation inside and
out. Significantly, there is no poly vapour barrier installed on the interior face, and no moisture
barrier on the exterior. An air space is provided between the exterior insulating panel and the
protective siding to prevent trapping moisture. The wood fibre insulation combines good
hygroscopic absorption of moisture with vapour permeability (May, 2005); because the
construction is consistent throughout the wall, there are no impediments to the transmission of
water vapour from the interior to the exterior. It may be expected that the NDW wall, if used
exclusively with materials compatible in hygroscopicity and vapour permeability, will contribute
BREATHING ROOM 23
to its own maintenance in preventing water collection in the building frame and therefore mould
growth.
The CLT (cross-laminated timber) wall is constructed from timber panels stacked and
glued into a solid mass panel; its behavior will approximate heavy timber construction. When it
is combined with a wood fibre rigid insulation on the exterior, and finished in the same manner
as the NDW wall, it should provide a degree of hygroscopic ability and vapour permeability
necessary to allow the free flow of moisture throughout the assembly. Although the vapour
permeability of a solid wood can be expected to be less than that of wood fibre, it can be
postulated that a comparable ability for hygroscopic absorption (May, 2005) would show
equivalent results. The increased density of solid wood should allow more water to be absorbed
than through wood fibre, balancing the slower rate of absorption.
SIPs (structural insulated panel) walls are composed of two sheets of OSB with an EPS
(expanded polystyrene) core. As they are composed mainly of insulating foam, do not have the
hygroscopic abilities and permeability of the wood fibre and CLT walls. Moisture that is
absorbed by the OSB will not be passed through the EPS and can only be absorbed by the OSB
to be released under lower RH conditions. This expectation may be problematic under continual
high humidity conditions, and lead to degradation of the OSB face. Performance may be
enhanced if an additional layer of plywood is added to the inside face. Due to its higher moisture
resistant rating (ISO, 2007) an added layer of plywood may be able to offset potential moisture
problems faced by the OSB by resisting vapour absorption. The additional bulk of added
plywood would also increase the amount of facing material able to absorb excessive moisture.
BREATHING ROOM 24
Analysis and Discussion: Part Two
One of the problems considered when this experiment was initially built was if the semi-
arid (Government of British Columbia, 2011) outdoor conditions in Kamloops, BC would have
an effect on the levels of humidity in the shed interior. Specifically, it was speculated that
humidity might not reach optimal levels for mould growth if 1- air leakage promoted loss of
moisture to drier outside conditions, and if 2- the bare wood fibre and CLT walls, through vapour
dispersal, skewed the results for the SIPs and 2” x 6” stud-framed wall.
Weather Conditions
Environment Canada statistics for Moosonee, Ontario were considered from the months
of April through October. Moosonee is located 220 km south of Attawapiskat and is a similarly
isolated community also located near James Bay. Its weather conditions can be considered
comparable and are used as records for Attawapiskat are not available. Through these months
there was an average temperature variance of 17.8oC, and an overall average temperature of
8.3oC. During the six week testing period, the outside temperatures in Kamloops varied by 17oC;
the overage average temperature of 7.5oC. The outside humidity ranged widely in Kamloops
from a low of 36% to a high of 91%, averaging at 62% RH. This is somewhat comparable to the
spring and summer months in Moosonee where humidity will range from 50% to 95%, averaging
around 70% RH.
Analysis of outside weather conditions as compared to inside rooms conditions do not
show any immediate correlation beyond the observation that when there were no heat sources
inside the shed, i.e. when the vaporizer and lamp were turned off, the interior lost heat over a
period of several hours. As this loss amounted to only 3oC over 48 hours, it can be reasoned that
BREATHING ROOM 25
the insulation of the structure contributed greatly to maintaining the established interior
conditions.
Air Leakage
In response to the second considered problem of air leakage, the interior of the shed was
heavily sealed with construction caulking in wall corners, and bottom seams where the walls met
the floor. The top of the shed was covered with a layer of poly, another lightweight tarp, and the
insulated roof. These three layers provided some sealing against air leakage. On the outside, the
corners were sealed with building tape before adding the aluminum siding. As the exterior
conditions were not seen to be influential on interior results, air leakage, as well, was not
considered to have been a significant factor. Therefore, the exterior conditions for the shed were
considered to be reasonable and applicable to the Attawapiskat area.
Interior Conditions
The interior conditions of the shed were kept at levels sufficient to promote mould
growth. There was no concentrated attempt to simulate real life conditions in this project due to
time constraints and the limited research scope prescribed by the program of study. The limited
simulation involved hammering two nails into each wall, and cycling the periods of light and
humidity. The damage caused by the nails was intended to approximate typical damage done in
a residence by the occupants. The intermittent periods of light and humidity simulated occupant
related activities at different times of the day. Due to the small interior size of the shed, a steady
room temperature of 20oC was easily maintained, and extreme conditions of humidity quickly
developed. The extreme humidity and wetting was considered desirable to accelerate mould
growth within the limited time available. In addition, this excessively wet condition suggests
possible conditions most likely to occur in a poorly ventilated residential washroom where
BREATHING ROOM 26
mould is often seen, and any success in this specific area can be assumed to be valid for other,
less moisture-prone areas of the building.
Conclusions
With correct construction, proper maintenance, and average urban conditions, all walls
tested are serviceable for daily living and are used in residential and commercial applications. In
Attawapiskat, standard construction has failed to resist mould growth on a wide-spread basis,
due to extreme conditions to which it is subjected. The purpose of this investigation has been to
propose a commercially available alternative that promises to meet the particular requirements of
the area and test that hypothesis under extreme conditions.
The extreme conditions used were interior surface wetting and humidity in excess of
what would normally be expected on a consistent basis in an Attawapiskat residence, but which
could be expected to occur occasionally. In addition to extreme conditions, minor surface
damage was inflicted upon the walls to simulate the type of day-to-day damage likely to occur in
the home.
In the 2” x 6” stud-framed wall, the results were consistent with prediction. By
puncturing the vapour barrier with the nail, moisture was able to able to enter the wall structure
where the mineral batt insulation was able to transfer, but not absorb, moisture. As a result, most
moisture wall was pulled by gravity to the bottom of the frame, where it was absorbed by the
wood frame. With the warm air, mould spores were in an ideal state of heat, moisture, and
nutrients, and were able to develop into mould that spread through the interior face.
In the SIPs wall, the moisture was absorbed by the OSB, but was unable to pass through
the solid foam core. As the mould growth was concentrated in the lower half of the wall, it can
be assumed that much of the moisture was absorbed from the bottom of the wall where
BREATHING ROOM 27
condensation may have pooled. The rate of transference of moisture from the lower to higher
areas of the wall appeared to be lower than the rate of mould spore development. Under these
circumstances, the SIPs wall would have better resistance with a securely sealed vapour barrier;
holes in the vapour barrier would allow mould growth to occur, but over a much smaller area.
The CLT wall showed good resistance to mould growth. It is expected that the
hygrothermal qualities of the wood allowed the wall to absorb much of the moisture; any
moisture transferred to the outside of the frame would have been able to be evenly dispersed by
the wood fibre external insulation to the surrounding environment. However, it did show some
mould growth within the initial three week period. It is speculated that the adhesive content of
the CLT wall inhibited full hygroscopic functioning of the wood, allowing moisture to become
trapped and available to developing mould spores. Vapour barriers would not be recommended
for the CLT wall, as its superior resistance is dependent on the ability of the wood to freely
absorb, and release moisture.
The NDW wall exhibited full resistance to visible mould growth within the initial three
week period. It can be assumed that during this time, the wall structure was able to absorb all
contacting moisture and freely transfer it through the assembly to the exterior wood fibre
insulation where it was dispersed to the surrounding air. By the end of testing, however, it did
show some mottling over the surface. This could have been due to the excessive condensation
from the roof, which showed signs of pooling on the top and front surfaces of the wall. It is
possible that this pooling effectively concentrated large amounts of water in the inside layer of
the wall, leading to mould spore development. A vapour barrier would not be advised for the
NDW wall, due to its high rate of absorption and transference of moisture. Compatible
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construction with like materials would enhance its natural abilities by limiting areas likely to trap
moisture.
Recommendations for Attawapiskat
Both the NDW wall and the CLT wall exhibited limited areas and light concentrations of
mould growth on their surfaces after six weeks of extreme humidity and wetting conditions. In
addition, both walls have low maintenance requirements. However, the NDW wall is the first
recommendation for Attawapiskat due to its resistance to mould growth within the initial three
week period, and its greater ease of construction. The standard 2” x 6” stud-framed wall and the
SIPs wall are not recommended because of their susceptibility to mould growth from surface
damage and adverse conditions.
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Glossary
1. The term “2” x 6” stud-framed wall” or “conventionally framed wall” refers to what
is known also as a “stick frame” wall in the construction industry. See appendix for
diagram
2. NDW or Naturally Different Wall refers to a type of wall manufactured in Alberta,
composed of wood framing and wood fibre insulation inside and out. It does not use 6
mil poly for a vapour barrier or building papers for moisture control. See appendix
for diagram
3. SIPs wall refers to a structural insulated panel wall comprised of 2 OSB panels on
either side of a rigid foam core. See appendix for diagram
4. CLT wall refers to a cross-laminated timber wall composed of layers of wood panels
stacked and glued at 90o angles, then vacuum pressed into a solid mass. See appendix
for diagram
5. “Poly” refers to 6 mil polyethylene sheet material, commonly used as a vapour barrier
in construction.
6. OSB is oriented strand board- a structural engineered wood product.
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Appendix A
Building Details
Figure 8: Cross-section of standard wall
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Figure 9: Cross-section of SIPs wall
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Figure 10: Cross-section of CLT Wall
Exterior Face
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Figure 11: Cross-section of NDW wall
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Figure 12: Section of Experimental Shed
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Appendix B
Photos of Mould Growth after 3 weeks
Figure 13: SIPs to CLT corner
Figure 14: Bottom of SIPs wall
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Figure 15: Bottom of Stud-Stud-framed Wall
Figure 16: Stud-Frame to NDW corner
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Photos of Mould Growth at 6 Weeks with Analysed Patterns
Table 1: Mould Coverage and Intensity
Wall Examined Count Total Area Ave.Size Particle % Area Mean
2” x 6” Stud-framed Wall
162 8263 51.006 1.299 61.434
SIPs Wall 497 13919 28.006 2.629 255
CLT Wall 277 5057 18.256 0.92 255
WF WALL 180 3156 17.533 0.824 255
Figure 17: 2” x 6” Stud-framed Wall and Mould Growth
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Figure 18: SIPs Wall and Mould growth
Figure 19: CLT Wall and Mould Growth
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Figure 20: NDW wall and Mould Growth
Table 2: Average Temperatures for Moosonee, ON-abridged (Environment Canada, 2000)
Temperature: Apr May Jun Jul Aug Sep Oct
Daily Average (°C) -2.4 6.2 11.9 15.4 14.4 9.4 3.4
Daily Maximum (°C) 3.7 12.7 18.8 22.2 20.8 14.6 7.6
Daily Minimum (°C) -8.6 -0.3 5 8.5 7.9 4.1 -0.8
Rainfall (mm) 20.6 46 70.4 101.3 75.8 88.7 59.1
Snowfall (cm) 19.2 6.9 0.7 0 0 1 14.9
Precipitation
39 53.7 71.1 101.3 75.8 90 73.3
Extreme Humidex 29.6 36.8 39.3 44.7 43.4 40.8 28.8
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Appendix C Table 3: Advisers and Sponsors
Advisers
Mindy Marshall
Dan Bissonnette
Tom Haag
Shannon Smyrl
Duane Svendson
Jaret Nield
Bill Billups
Dave Gardner
Dr. Jieying Wang
−Faculty of Science Mentor
−Faculty of Science Mentor
−Carpentry Mentor
−Writing Mentor
−Project Sponsor & Advisor
−Project Advisor
−Project Advisor
−Project Advisor
−Research Advisor
Company/Department
Architectural & Engineering Technology
Physics & Astronomy School of Trades & Technology English and Modern Languages Trout Creek International Homes In & Out Water and Construction Technical Advisor, Canadian Wood Council Wood WORKS! BC Heavy Timber Specialist Structurlam Products Ltd. Senior Scientist, FPInnovations – Wood Products Division
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Sponsors Donated Jerry Boyetchko Northern Trailer finished 2” x 6” stud-framed wall Duane Svendson Trout Creek International Premier Structural Insulated
Homes Panel Wall
Tom Haag Thompson Rivers 2- 2” x 6” stud-framed walls University Bill Downing President Structurlam Products Ltd. Structurlam Cross Laminated Timber Wall Peter Graul Woodpecker European Naturally Different Wall panel
Timber Framing Ltd. / Woodpecker Homes Ltd
James Bennett Dulux Paints Dulux Interior Paint wood pallets
James Rees Home Hardware Asphalt Shingle Roofing
