USG Moisture, Mold, and Construction Practices Frequently Asked Questions - Manual

Understanding the impact of moisture and mold on building materials and the construction process is integral to
developing 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 relationship between the con-
struction environment and the performance of building materials. Throughout this document, you’ll find references
to additional sources that reinforce good design, construction and maintenance practices to limit the growth of
mold in any building environment. If you have additional questions, contact those sources or USG.
1. What conditions are necessary For mold to grow on or in a material, water, spores and a food source must be present.
for mold to grow?
2. Do building materials support Yes, but only when they get wet. Mold can grow in or on virtually every construction material. This includes glass
the growth of mold? fiber insulation, lumber, carpet, fabric, vinyl wall coverings, paint, OSB, plywood, EIFS, siding, wallboard, ceiling
panels and brick. When a building material gets wet and dirty, it becomes a target for mold growth. Even products
such as aluminum, steel and glass will support mold growth under the right conditions.
3. What is mold and where is it found? Mold (fungi) is present everywhere—indoors and outdoors. There are more than 100,000 species of mold.
At least 1,000 species of mold are common in the United States including Cladosporium, Penicillium and
Aspergillus. Mold is most likely to grow where there is water or dampness such as in bathrooms and basements.
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4. How can mold affect your health? Most types of mold are not hazardous to healthy individuals. However, excessive exposure to mold 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’s vulnerability, more serious health effects—such as fevers and breathing problems—
can occur, but are unusual.
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5. Why am I hearing more about To our knowledge, no studies have been done to quantify the prevalence of mold in current or past construction.
mold than I have in the past? Heightened focus on the subject in the media has brought more attention to the construction industry and all
trade factors on the need to employ good design, construction and maintenance practices that will minimize
risk of water damage and mold.
Some investigators have speculated that the “tighter” 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. 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 provided. As a result, many buildings
are open to the elements during all phases of construction. This practice can introduce a great deal of moisture
into a building. In fact, standing water has become commonplace on many job sites. With spores naturally present
in the environment and limited or no protection from water on many projects, mold growth can readily develop on
and in building materials.
Moisture, Mold, and
Construction Practices
System
Performance
Frequently Asked Questions
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