The crawl space under the floor of a home is a ticking time bomb of potential problems. That short,
basement-like space with the dirt floor that many homeowners would rather forget is in many instances a welcome home to moisture-loving pests like carpenter ants and termites as well as health-jeopardizing problems like molds, mildews and soil gases.
Crawl spaces are often damp, humid spaces due to water runoff from rain, irrigation systems or an elevated water table. While the building code requires crawl space ventilation, this ventilation does virtually nothing to mitigate moisture problems and can actually make moisture problems worse.
Houses operate like chimneys.
If you introduce a hole at the bottom of a chimney, a natural draft ensues as air exits the top of the chimney. This is called stack effect. Attic ventilation is the top of the chimney and crawl space ventilation is the bottom. As air is drawn up through your house, moisture, mold spores, odors and soil gases from the crawl space find their way into the living space.
Crawl space encapsulation involves sealing the under side of the floor with Polyurethane spray foam and sealing the inside of the crawl space using a tough, reinforced polyethylene
sheeting taped carefully at the seams and adhered to the top of the concrete foundation wall
and sealing up all ventilation entering the crawl space. Sealed below the sheeting are soil gases, moisture, water vapor and odors that typically would be drawn up into the living space above.