All building materials, when installed to create a building envelope assembly, work interactively as a system. The purpose of which controls the movement of heat, air, and moisture. When not properly designed or installed, moisture can move through the building envelope. This moisture condenses on cold surfaces that are below the dewpoint temperature or create high levels of moisture. Additionally, this moisture, at certain temperatures, can provide the conditions necessary to promote the growth of mold and mildew. Such moisture also requires the presence of organic food sources (paper, wood, bacterial dust, etc.)
Spray foam is not a source of food for mold, mildew, and bacteria. However, organic dust can collect on the surface of the foam. In combination with moisture at the right temperatures, these organic dust can result in mold and mildew. Spray foam, like all insulation products, can result in mold and mildew problems in building envelopes that are poorly designed or constructed. Proper air sealing, as well as use and placement of vapor retarders, and sufficient levels of insulation are key to proper building envelope design.
