Good Design Practices
Moisture, Mould, Mildew and
Construction Practices
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Frequently Asked Questions
Understanding water, mould and mildew and their impact on the construction process and building materials are
integral to good design and construction practices.
This document summarizes research and information developed by a variety of organizations such as the American
Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), the United States Environmental
Protection Agency (EPA) and the New York City Department of Health (NYCDH). A complete listing of agencies can
be found at the end of this document.
The following questions and answers will help you develop an understanding of the construction environment, and
the relation of building materials to it. Throughout this document you鈥檒l find references to additional sources that
reinforce good design, construction and maintenance practices. These practices are generally recognized as
necessary to limit the growth of mould and mildew in any building environment. If you have additional questions,
contact those sources or CGC.
1. What conditions are necessary for For mould and mildew to grow on or in a material, water, spores and a food source must be present.
mould and mildew to grow?
2. Do building materials support Yes, but only when they get wet. Mould and mildew grows in or on virtually every construction material currently
the growth of mould and mildew? made. This includes glass fiber insulation, lumber, carpet, fabric, vinyl wall coverings, paint, OSB, plywood, EIFS,
siding, wallboard, ceiling panels and brick, to name a few. Given the right conditions, virtually any building material
can be overwhelmed by mould.When a building material gets wet and dirty, it becomes a target for mould and mildew
growth. Even products such as aluminum, steel and glass will support mould growth under the right conditions.
3. What is mould and where is it found? Mould (fungi) is present everywhere鈥攊ndoors and outdoors. There are more than 100,000 species of mould.
At least 1,000 species of mould are common in the United States and Canada. Some of the most commonly found
mould are species of Cladosporium, Penicillium and Aspergillus. Mould is most likely to grow where there is water
or dampness such as in bathrooms and basements.1
4. How can mould affect your health? Most types of mould are not hazardous to healthy individuals. However, excessive exposure to mould may cause or
worsen conditions such as asthma, hay fever or other allergies. The most common symptoms of overexposure
are cough, congestion, runny nose, eye irritation and aggravation of asthma. Depending on the amount of
exposure and an individual鈥檚 vulnerability, more serious health effects 鈥? such as fevers and breathing problems 鈥?
can occur, but are unusual.1
5. Why am I hearing more about To our knowledge, no studies have been done that would quantify the prevalence of mould in current or past
mould and mildew than construction. Because there has been a heightened focus on the subject in the media, it has brought more
I have in the past? focused attention on the construction industry and all trade factors to employ good design, construction and
maintenance practices that will minimize risk of water damage and mould and mildew.
Some investigators have speculated that the 鈥渢ighter鈥? construction practices adopted to conserve energy in the 70s
have led to a greater potential to trap moisture in wall cavities and elsewhere. In addition, construction schedules
have been continually shortened as owners and developers focus on more time-efficient construction practices
to minimize their carrying costs during construction. In part, this shortening of construction schedules contributes to
installation conditions being less than ideal. In many cases, short-term protection from water is not offered. As a
result, many buildings are open to the elements during all phases of construction. This practice introduces a great
deal of moisture into a building. In fact, standing water has become a common occurrence on many job sites.
With spores naturally present in the environment and limited or no protection from water, mould and mildew growth
can occur on and in building materials.
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6. What environmental conditions Unfortunately job site conditions are critical in the application and finishing of our products and are beyond our
are needed for the application control. We strongly recommend eliminating any excess moisture or water on your project to minimize risk of water
and finishing of gypsum panels? problems such as mould and mildew. In addition, please refer to ASTM C840 the Standard Specification for
Application and Finishing of Gypsum Board. This information assists the design professional and professional
contractor, in conjunction with project specific information, in understanding the relationship between the project
environment and the ability to insure the performance of our materials. For complete CGC application recommenda-
tions, please refer to the USG Gypsum Construction Handbook, Centennial Edition.
7. Are CGC鈥檚 drywall products No. Although we have introduced many improvements over the years, CGC has not altered its SHEETROCK 庐
more susceptible to mould and Brand Gypsum Panel products in any way that would make them more susceptible to mould and mildew.
mildew today?
8. Why doesn鈥檛 CGC make a mould and Any building material can be overwhelmed by mould and mildew given the proper conditions. Products and systems
mildew PROOF drywall? can be designed to incorporate increasing degrees of mould and mildew resistance, but to completely eliminate the
possibility of mould growth under moist conditions would require the application of anti-fungal agents which themselves
pose potential health risks and are very expensive. The best and most cost-effective strategy to manage the growth
of mould and mildew is to prevent the intrusion of water into the building.This can be accomplished by utilizing good
design, construction, and maintenance practices. However CGC does manufacture SHEETROCK Brand HUMITEK
Gypsum Panels that offer increased resistance to mould but like all building products there is no guarantee against
mould growth.
9. Which CGC products and CGC ASTRO鈩? CLIMAPLUS鈩? and ECLIPSE鈩? Ceiling Panels with AEGIS鈩? Microbe Shield and SHEETROCK 庐 Brand HUMITEK
systems offer enhanced mould Gypsum Liner Panels (for use in SHEETROCK Brand Cavity Shaftwall and Area Seperation Wall Systems) and SHEETROCK
and mildew resistance? Brand HUMITEK Gypsum Panels; FIBEROCK Brand Underlayment-AQUA TOUGH and FIBEROCK Brand Sheathing-AQUA TOUGH;
and DUROCK Brand Cement Board offer mould and mildew resistance.These products are specifically designed to meet
discrete acoustical, aesthetic and environmental performance criteria while providing mould and mildew resistance (as
tested and reported per ASTM D3273-00) when installed using good design and construction practices. See product
literature for specific warranty language, limitations and exclusions.
10. Is CGC developing additional CGC has a long history of bringing new and innovative products to market. These products are designed to be
product responses for mould and safe during manufacturing, delivery, handling, and installation, and to perform well when installed and
mildew? maintained using good construction practices. All product development efforts continue to focus on ensuring the
safety, quality and performance of our products. This commitment to safety and an accurate portrayal of our
products鈥? performance and their limitations are the cornerstones of CGC鈥檚 product development process. As new
and innovative products, such as SHEETROCK Brand HUMITEK Gypsum Panels and systems are developed and tested,
they will be released to the market.
11. Does CGC plan to offer a mould and No. CGC does not plan to offer enhanced mould and mildew resistance on drywall products used in dry environments.
mildew resistant drywall panel CGC鈥檚 SHEETROCK Brand Gypsum Panels have a long history (over 85 years) of excellent performance when installed and
for use in a dry environment? maintained using good construction and maintenance practices. Any product development efforts would be focused on
improving the mould and mildew resistance of products that could reasonably be expected to encounter water during
the construction process. If a product is not expected to get wet it is not necessary to use products with mould
resistance built in. If there is a chance of the product coming into contact with reasonable amounts of water then
SHEETROCK Brand HUMITEK Gypsum Panels will offer added resistance to mould growth.
Moisture, Mould, Mildew and Construction Practices (FAQs)
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12. What else is CGC doing to address CGC鈥檚 efforts to address these issues fall into three categories:
the issues of water, mould, and Research Perform ongoing research to better understand the impact of construction practices, water and mould and
mildew growth? mildew on our products and systems.
Assistance Provide assistance to respected authorities and associations to aid in developing a broader understanding of
construction systems and appropriate test methods for those systems.
Education Educate individuals who occupy buildings made with our products and systems and those who are involved
in the manufacture, distribution, installation and maintenance of the same products and systems on central issues
pertaining to water, mould and mildew.These issues include product safety, good materials storage and handling, good
design and construction practices, water management, and proper building maintenance.
13. Who can help me decide if CGC actively participates in educating our customers about the proper design, specification, installation and
I have a problem on my job site? maintenance of our products. We have a variety of internal and external resources to help you make appropriate
decisions regarding specific conditions for your projects. However, CGC does not offer inspection or mould testing
services.
14. Is moisture content a critical Yes. We precisely control the board鈥檚 moisture to ensure that the product meets our stringent performance
element in the gypsum board standards. However, once a building material begins its journey to a project, environmental conditions can sometimes
manufacturing process? make it difficult to control moisture content. For that reason, we have a long-standing history of transport, storage,
handling, application, finishing and maintenance recommendations that clearly advise keeping our products clean
and dry. For specific recommendations, please refer to the USG Gypsum Construction Handbook, Centennial Edition.
15. What is the acceptable moisture Currently there is not an industry standard for measuring gypsum board moisture content at a job site. Addressing
content for gypsum board on the overall moisture impact on the entire project is the appropriate approach. Moisture can affect not only
a job site? installation, but also the finished appearance of a gypsum board partition or ceiling. At any point in the construction
process, minimizing moisture exposure is the key to maximizing the performance of the finished assembly.
16. What are the basics of It is important to dry water-damaged areas within 24-48 hours to prevent mould growth. In all situations, immediately
cleaning the affected area? identify and address the cause of water damage to prevent re-occurance of the problem. For more information
please refer to CGC鈥檚 鈥淩epairing Water-Damaged Building Systems鈥? (EWB-0W95) literature.
17. Who does CGC recommend CGC does not offer specific company endorsements for remediation at this time. However, we suggest reviewing
for assistance in cleaning 鈥淕uidelines on Assessment and Remediation of Fungi in Indoor Environments鈥? from the New York City
affected areas? Department of Health Bureau of Environmental & Occupational Disease Epidemiology. These guidelines are
available at nyc.gov/html/doh/html/epi/moldrpt1.html.
You may also call your local Canada Mortgage and Housing Corporation office for a list of individuals who have
completed the CMHC Residential Indoor Air Quality Investigator Program.
Moisture, Mould, Mildew and Construction Practices (FAQs)
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What are moulds?
The following questions and answers
Moulds produce tiny spores to reproduce. Mould spores waft through the indoor and outdoor air continually. When
are excerpted with permission from the
mould spores land on a damp spot indoors, they may begin growing and digesting whatever they are growing on
New York City Department of Health:
in order to survive. There are moulds that can grow on wood, paper, carpet and foods. When excessive moisture
or water accumulates indoors, mould growth will often occur, particularly if the moisture problem remains
undiscovered or unaddressed. There is no practical way to eliminate all moulds and mould spores in the indoor
environment; the way to control indoor mould growth is to control moisture.2
How does mould grow?
All moulds need water to grow. Mould can grow almost anywhere there is water damage, high humidity or damp-
ness. Most often moulds are confined to areas near the source of water. Removing the source of moisture 鈥? such
as through repairs or dehumidification 鈥? is critical to preventing mould growth.
What should you do if mould is present in your home or apartment?
Although any visible mould can be sampled by an environmental consultant and/or analyzed by a laboratory
specializing in microbiology, these tests can be very expensive 鈥? from hundreds to thousands of dollars. There
is no simple and cheap way to sample the air in your home to find out what types of mould are present and
whether they are airborne. Even if you have your home tested, it is difficult to say at what levels health effects
would occur. Therefore, it is more important to eliminate the mould rather than find out more about it. The most
effective way to treat mould is to correct underlying water damage and clean the affected area.
How should mould be cleaned?
Mould should be cleaned as soon as it appears. Persons cleaning mould should be free of symptoms and allergies.
Small areas of mould should be cleaned using a detergent/soapy solution or an appropriate household cleaner.
Gloves should be worn during cleaning. The cleaned area should then be thoroughly dried. Dispose of any sponges
or rags used to clean mould.
If the mould returns quickly or spreads, it may indicate an underlying problem such as a leak. Any underlying water
problems must be fixed to successfully eliminate mould problems. If mould contamination is extensive, a profes-
sional abatement company may need to be consulted.
Who can I call if I suspect I have a mould problem or if I want more information?
For more information about the health effects of mould exposure and information on the safe removal of mould,
please call the New York City Department of Health, Office of Environmental Investigations at (212) 442-3372
or the Environmental and Occupational Disease Epidemiology Unit at (212) 788-4290.
鈥? Certified HVAC Hygienist
Footnotes 鈥? CMHC, www.cmhc.ca 鈥? Manufactured
(CHH) Certification has been
鈥? Health Canada, www.hc-sc.gc.ca
1.New York City Housing Institute
changed to the Certified
鈥? U.S. Environmental
Department of Health www.mfghome.org/
Indoor Environmentalist
Protection Agency
www.ci.nyc.ny.us/html/ home.html
(CIE) Certification
www.epa.gov/iaq
doh/html/epi/epimold.html 鈥? University of Minnesota,
鈥? IICRC - Institute of Inspection,
鈥? New York City
2.U.S. Environmental Department of Environmental
Cleaning and Restoration
Department of Health
Protection Agency Health & Safety
www.iicrc.org
www.ci.nyc.ny.us/html/doh/
www.epa.gov/iaq/ www.dehs.umn.edu/iaq
鈥? ASCR - Association of
html/epi/epimold.html
pubs/moldresources 鈥? IAQA - Indoor Air Quality
Specialists in Cleaning
鈥? APA - The Engineered Association
and Restoration
Wood Association
Additional Resources www.iaqa.org
(CR - Certified Restorer)
www.apawood.org
鈥? CGC Technical Assistance
WLI - Water Loss Institute
鈥? ASHRAE
1-800-387-2690 The following organizations
(Division of ASCR)
www.ashrae.org
www.cgcinc.com also offer certification
www.ascr.org
鈥? National Research Council of 鈥? Gypsum Association programs for remediation
www.ascr.org/wli.asp
Canada Institute for Research in www.gypsum.org specialists:
鈥? NAHB Research Center
Construction Indoor 鈥? IAQA Certified Indoor
www.nahbrc.org
Environmental Program Environmentalist
www.nrc.ca/irc/ie www.iaqa.org/ciecert.htm
CGC Inc. EWB-0W96/05-02 CP
350 Burnhamthorpe Rd., W. www.cgcinc.com
漏 2002, CGC Inc.
5th Floor
Printed in Canada
Mississauga, ON
L5B 3J1
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