Implications for Good Building Practices for Dampness and Mold

Given the extensive evidence that the risks of asthma-related and respiratory health effects are substantially increased in damp or moldy buildings, the Institute of Medicine Committee that reviewed the risks of damp and moldy buildings came to the following conclusions [1]:

“Homes and other buildings should be designed, operated, and maintained to prevent water intrusion and excessive moisture accumulation when possible. When water intrusion or moisture accumulation is discovered, the source should be identified and eliminated as soon as practicable to reduce the possibility of problematic microbial growth and building material degradation.  The most effective way to manage microbial contaminants, such as mold, that are the result of damp indoor environments is to eliminate or limit the conditions that foster its establishment and growth.”

The committee also concluded:

“When microbial contamination is found, it should be eliminated by means that not only limit the possibility of recurrence but also limit exposure of occupants and persons conducting the remediation.”

The World Health Organization Committee came to similar conclusions [2] and stated “Well-designed, well-constructed, well-maintained building envelopes are critical to the prevention and control of excess moisture and microbial growth….”.

Based on the prior review of the Nature and Causes of Building Dampness, many practices necessary to reduce dampness problems are self evident. For example, building maintenance should be performed to minimize the chances of developing water leaks in building envelopes and plumbing systems, and identified leaks should be quickly fixed. Also, building construction materials should be protected from the rain. Exhaust fans should be used to remove the moisture produced during cooking, showering, and similar activities. It would also help to reduce the construction of buildings in flood-prone areas. Ground water and drainage from roofs should be directed away from building foundations. Mechanical equipment (e.g., HVAC systems) should be designed and operated to maintain indoor humidity levels within acceptable limits (e.g., 30% to 60% relative humidity) and dehumidification will often be necessary in hot humid climates. However, in addition to these common-sense measures, many non-obvious changes in building design, construction, operation, and maintenance can reduce building dampness problems. It is beyond the scope of this web site to provide such detailed guidance; however, much guidance is available in the published literature.

Examples of related topics and references follow:

• vapor and air barriers [3, 4]
• building envelope design [3-7]
• basement moisture control [8]
• dehumidification by HVAC systems [9-15]
• moisture control principles for residential and small commercial buildings [16]
• humidity control design guidance for commercial and institutional buildings [10]

The U.S. Environmental Protection Agency also provides a broad range of information about dampness and mold problems, their associated health risks, prevention and remediation practices, and clean ups after a flood. Detailed specifications for moisture control in new houses is available in the EPA Indoor airPLUS Construction Specifications.

1.         IOM, Damp indoor spaces and health, Institute of Medicine, National Academy of Sciences. 2004, Washington, D.C.: National Academy Press.

2.         World Health Organization, WHO Guidelines for indoor air quality: dampness and mold. 2009, World Health Organization regional office for Europe: Copenhagen, Denmark.

3.         Lstiburek, J.W., Understanding vapor barriers. ASHRAE Journal, 2004. 46: p. 40-50.

4.         Lstiburek, J.W., Understanding air barriers. ASHRAE Journal, 2005. 47: p. 24-30.

5.         Lstiburek, J.W., Understanding drainage planes. ASHRAE Journal, 2006. 48: p. 30-35.

6.         Lstiburek, J.W., The perfect wall. ASHRAE Journal, 2007. 49: p. 74-78.

7.         Lstiburek, J.W., The perfect storm over stucco. ASHRAE Journal, 2008. 50: p. 38-43.

8.         Lstiburek, J.W., Understanding basements. ASHRAE Journal, 2006. 48: p. 24-29.

9.         Shirey, D.B., H.I. Hendersen, and R.A. Raustad, Understanding the dehumidification performance of air-conditioning equipment at part-load conditions: Final report.  FSEC-CR-1537-05. 2006, Florida Solar Energy Center: Cocoa, Florida.

10.       Harriman, L., G. Brundrett, and R. Kittler, Humidity control design guide for commercial and institutional buildings. 2001, Atlanta, GA: ASHRAE.

11.       Harriman, L.G., The dehumidification handbook, 2nd Edition. 1990, Amesbury, PA: Munters Cargocaire.

12.       Gatley, D.P., Dehumidification enhancements for 100-percent outside air AHUs, Part 1, Simplifying the decision-making process. HPAC Engineering, 2000. September 2000: p. 28-32.

13.       Gatley, D.P., Dehumidification enhancements for 100-percent outside air AHUs, Part 2, Recuperative heat exchange is an energy-efficient way to accomplish reheat while also reducing cooling capacity. HPAC Engineering, 2000. October 2000: p. 51-59.

14.       Gatley, D.P., Dehumidification enhancements for 100-percent outside air AHUs, Part 3, Enthalpy heat exchange, the use of desiccants, and vapor compression dehumidifiers are cost effective ways to maintain healthy and comfortable buildings. HPAC Engineering, 2000. November 2000: p. 31-35.

15.       Hendersen, H.I., D.B. Shirey, and R.A. Raustad, Understanding the dehumidification performance of air-conditioning equipment at part-load conditions, in CIBSE/ASHRAE Conference. 2003: Edinburgh, Scotland.

16.       Lstiburek, J.W. and J. Carmody, Moisture control handbook: principles and practices for residential and small commercial buildings. 1993, New York: Van Nostrand Reinhold. 214.