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By: Robert Grupe
Director, Architectural and Technical Solutions, United States Gypsum Company

Phil Shaeffer
Manager, Codes and Technical Support, United States Gypsum Company

Dean Updegrove
Product Marketing Manager, United States Gypsum Company

The additional reading materials required for USG Corporation's Gypsum Cavity Shaft Wall Systems - the Standard for Life-Safety in Low-, Mid- and High-Rise Construction include two sections:

• A discussion of mold, mildew and construction practices;
  
• A look at design considerations for horizontal shaft wall installations.

Section 1

MOISTURE, MOLD, MILDEW AND CONSTRUCTION PRACTICES

With increasing attention being paid to the potential for mold and mildew growth in nearly all aspects of building design and construction, the following topics should be taken into consideration when specifying and managing construction of cavity shaft walls. The information is culled from research developed by a variety of organizations, including the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), the U.S. Environmental Protection Agency (EPA) and the New York City Department of Health (NYCDH).

1. What conditions are necessary for mold and mildew to grow?

For mold and mildew to grow on or in a material, water, spores and a food source must be present.

2. Do building materials support the growth of mold and mildew?

Yes, but only when they get wet. Mold and mildew grows in or on virtually every construction material currently 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 mold. When a building material gets wet and dirty, it becomes a target for mold and mildew 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. Some of the most commonly found mold are species of Cladosporium, Penicillium and Aspergillus. Mold is most likely to grow where there is water or dampness such as in bathrooms or basements.

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 an exposure and an individual's vulnerability, more serious health effects - such as fevers and breathing problems - can occur, but are unusual.†

5. Why am I hearing more about mold and mildew than I have in the past?

Some investigators have speculated that the "tighter" construction practices adopted to conserve energy in the 1970s 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 in many job sites. With spores naturally present in the environment and limited or no protection from water, mold and mildew growth can occur on and in building materials.

6. What environmental conditions are needed for the application and finishing of gypsum panels?

To minimize the potential for mold and mildew growth, it is strongly recommended that any excess moisture or water on the job site be eliminated. In addition, specifiers should refer to ASTM C840, the Standard Specification for Application and Finishing of Gypsum Board. This standard discusses the relationship between the project environment and the ability of manufacturers to insure the performance of gypsum materials.

7. What is the acceptable moisture content for gypsum board on a job site?

Currently there is not an industry standard for measuring gypsum board moisture content at a job site. Addressing the overall moisture impact on the entire project is the appropriate approach. Moisture can affect not only 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.

8. What are the basics of cleaning an area affected by mold or mildew?

It is important to dry water-damaged areas within 24 to 48 hours to prevent mold growth. In all situations, immediately identify and address the cause of water damage to prevent re-occurrence of the problem.

† Source: New York City Department of Health

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