Many buildings incorporate vapor barriers in the design of their walls and floors. Vapor barriers must be located and installed properly or the building may have moisture problems. A vapor barrier is a layer of material that slows or prevents the absorption or release of moisture from or into a wall or floor. Vapor barriers can prevent damp or wet building materials from drying quickly enough to prevent mold growth.
Common moisture problems include: Leaking roofs. Leaking or condensing water pipes, especially pipes inside wall cavities or pipe chases. Leaking fire-protection sprinkler systems. Landscaping, gutters, and down spouts that direct water into or under a building. High humidity (> 60% relative humidity). Unvented combustion appliances such as clothes dryers vented into a garage (Clothes dryers and other combustion appliances should be vented to the outside).
The best way to resolve many of those issues is to install a vapor barrier, but first, you have to clean out all the damp, rotting insulation and other accumulated dirt and debris from the space like our crawlspace experts did here.