Sealed Crawl Space
A crawl space (as the name suggests) is a type of basement in which one cannot stand up — the height may be as little as a foot, and the surface is often soil. They offer a convenient access to pipes, substructures and a variety of other areas that may be difficult or expensive to access otherwise. While a crawlspace cannot be used as living space, it can be used as storage, often for infrequently used items. Care must be taken in doing so, however, as water from the damp earth, humidity entering from crawlspace vents, and moisture seeping through porous concrete will create a perfect environment for mold, mildew to form on any surface in the crawlspace, especially cardboard boxes, wood floors and surfaces, drywall and some types of insulation.
Health and safety issues must be considered when installing a crawl space. As air warms in a home, it rises and leaves through the upper regions of the house, much in the same way that air moves through a chimney. This phenomenon, called the “stack effect,” causes the home to suck air up from the crawlspace into the main area of the home. Mold spores and fecal material from dust mites in the crawlspace come up with the air, agitating breathing problems such as asthma and creating a variety of health-related problems.
It is usually desirable to finish a crawlspace with a plastic vapor barrier that will not support mold growth or allow humidity from the earth into the crawlspace. This helps insulate the crawlspace and discourages the habitation of insects and vermin by breaking the ecological chain in which insects feed off the mold and vermin feed on the insects, as well as creating a physical inorganic barrier that deters entrance into the space. Vapor barriers can end at the wall or be run up the wall and fastened to provide even more protection against moisture infiltration. Some pest control agencies recommend against covering the walls as it complicates their job of inspection and spraying. Almost unheard of as late as the 1990s, vapor barriers are becoming increasingly popular in recent years, in fact, the more general topic of conditioned vs. unconditioned crawlspaces has enjoyed much research over the last decade.