Indoor air quality (IAQ) is becoming an increasingly important issue in today's buildings. At first glance, providing and maintaining acceptable indoor air quality seems simple, but many factors from various controllable and uncontrollable sources influence the quality of the air inside buildings and make this seemingly simple concept somewhat complex. This paper focuses on one aspect of IAQ: mold and mildew growth. In particular, this paper discusses the role of relative humidity and temperature measurements for the prevention and detection of mold and mildew growth.

The growth of mold and mildew is a serious problem in buildings, especially those located in hot and humid climates. When these buildings are constructed similarly to buildings in cold climates, the combination of hot and humid climate coupled with an interior surface treatment, which is a vapor retarder, allows mold to grow behind the interior surface treatment. The mold and mildew create both indoor air quality and health-related problems. The American Hotel & Motel Association estimates this problem costs the industry approximately $68 million each year in lost revenues and repair.

Heat and moisture transmission through walls of typical concrete block construction exposed to hot and humid climates was studied in a recent research project sponsored by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Six wall sections with different interior and exterior surface treatments were exposed to indoor conditions of 70°F (21°C) and 50% relative humidity, while the exterior sides of the wall sections were exposed to hot and humid summer conditions of Brownsville, Texas. To assist in determining the moisture levels within the wall sections, capacitive-type polymer relative humidity (RH) sensors were placed at various locations through the wall construction. These RH sensors were not only located in the conditioning airstreams and wall air gaps but were also embedded in gypsum board. At the conclusion of these tests, the moisture levels behind the various interior surface treatments were compared, and the criteria for mold and mildew growth were evaluated.

The main objective of this paper is to inform building designers and engineers in the HVAC industry about the techniques used to determine and prevent mold and mildew growth. In addition, this article addresses the benefits, limitations, and implementation of the capacitive-type relative humidity sensor. Finally, a comparison of the various interior and exterior surface treatments and their role in mold and mildew prevention is presented.

Authors: Mike H. Wallis, Mohammad H. Hosni, Ph.D., Jerry M. Sipes, Ph.D., P.E.
Citation: IAQ and Energy 98 Using ASHRAE Standards 62 and 90.1 Conference Papers
Keywords: October, Louisiana, 1998