Six Ways for Condensation in Buildings

Apr 12, 2010

Six of the ways condensation can occur on cold surfaces in buildings are discussed here. They are:
1. Air Leakage,
2. Diffusion
3. Convection,
4. Thermal bridges
5. Fenestration
6. Ground contact

Each of these ways will be discussed in this paper and solutions suggested to mitigate and avoid the problems from occurring,

Preventing condensation, or more accurately, avoiding an increase in the moisture content of building materials to levels that can support the growth of microorganisms, especially molds within the enclosure and on interior surfaces, is fundamental to avoiding health and air quality problems in buildings; it is also essential in avoiding premature deterioration of enclosure components.

The growth or amplification of microorganisms in buildings not only results in biodeterioration of susceptible construction materials but also leads to the production of allergens and microbial VOCs (the cause of musty odors) that can affect occupant health and air quality. A complex microbial ecology (e.g., mites feed on mold and skin particles; other organisms feed on mites ) can develop in or on construction materials that are chronically wet or damp.

Allergens associated with molds and arthropods (their feces and body parts) growing in chronically wet construction niches can enter the indoor environment and pose a risk to sensitive occupants. The moisture content of building materials increases due to water vapor transport across enclosure assemblies, either by infiltrating, exfiltrating, or convecting air coming in contact with surfaces that have a temperature lower than the dew‐point of the moving air, and/or by diffusion due to a difference in water vapor pressure across the assembly, or by capillary transport through the microscopic voids in building materials.

Wagdy Anis, FAIA (WJE Associates Inc.)
Presented at: 
Building Enclosure Science & Technology (BEST2) Conference
Published & professionally reviewed by: 
WJE Associates Inc.
Building Enclosure Technology & Environment Council (National Institute of Building Sciences)

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