This is a process in which the entire crawl space area is sealed. The foundation vents are blocked and the entire foundation wall is covered with rigid insulated Styrofoam board and is then taped at the seams. The foam board is an insulator with an R value of 13. The entire crawl space floor and foundation walls are covered with a polyethylene vapor barrier designed for the crawl space environment. The vapor barrier is taped at the seams using a UV resistant polyethylene tape so that no moisture can pass from the ground to your home.
The concept is based on something called “the stack effect.” This is a natural phenomenon of constant movement of air through the house. Essentially warm air rises and finds its way to escape into the upper areas of a house and then outside. As the warm air leaves the building, cool air rushes in through leaky windows, doors, and crawl space vents to replace it and repeat the cycle. The air in the crawl space gets sucked up into the living area bringing with it moisture, dust, mold spores and allergens. This effectively eliminates any possibility of meaningful cross ventilation and negates the possibility of allowing moist air to leave through the vents. We’ve included a link to more technical data on this subject. www.buildingscience.com You can also vent a small amount of warm air into the crawl space to further protect from moisture. One advantage of insulating the foundation walls is you have eliminated the need for floor insulation.
There are still two schools of thought regarding this process. This system doesn’t fit every home. We’ll evaluate your home and help you decide the right solution for your crawl space. One word of caution here- if the crawl area is home to your hot water heater and/or furnace, these appliances need make up air for combustion and you must consult an HVAC professional before making a decision.