Basement and crawl space experts typically are in agreement that sealed crawl spaces are more energy efficient; resolve moisture, mold and rot problems; and stop insect infestations. The potential for misunderstanding arises when it comes to insulating one. An uninsulated crawl space, whether conditioned or not, is often a major source for heat loss in a home.
To get the most “bang for the buck,” insulate the crawl space walls, not the ceiling. If given the choice between the walls and ceiling, the Department of Energy says to insulate the walls, not the ceiling. Heat transfer always moves from hot to cold or from inside the home to outside and down into the crawl space. When insulating the crawl space, it is best to use an aluminum faced material to reflect heat back into the home.
Eliminate the moisture. It is important to install a vapor barrier, such as the EmeShield 60mil Pro Plus Liner, to keep moisture out. Moisture is what causes many of the problems with crawl spaces such as rot, mold and mildew.
Don’t use standard fiber glass insulation. Fiber glass insulation-especially backed insulation-is a food source for mold. If any moisture ends up in the crawl space, mold will grow and feed on the insulation.
Luckily, there are alternatives to fiberglass insulation.. One insulating product is an insulating blanket that is made of plastic on one side and aluminum on the other with either trapped air or closed cell foam between the two faces. This acts as a radiant heat shield or reflector that pushes the heat back into the home.
The radiant heat shield can be placed on the ceiling of the crawl space leaving a gap between the living space floors and the insulating blanket. Face the aluminum side up to reflect the heat that moves down into the crawl space from the living space above, back into the home. Within that gap, the rim joists around the perimeter of the home should be insulated with breathable, un-faced, formaldehyde-free, open cell foam insulation.
Make sure the insulation material is fire resistant. Check your local fire codes regarding exposed insulation. The aluminum insulating blanket mentioned above is treated with a fire retardant.