insulation in crawl spaces

[Deana M. Clark]

Here are some guidelines to follow for insulating a ventilated crawl space:

1. Carefully seal any and all holes in the floor above ("ceiling" of the crawl space) to prevent air from blowing up into the house.
2. Insulate between the floor joists with rolled fiberglass. Install it tight against the subfloor. Seal all of the seams carefully to keep wind from blowing into the insulation. Also, adequately support the insulation with mechanical fasteners so that it will not fall out of the joist spaces in the years to come. DO NOT just rely on the friction between the fiberglass and wood joists to secure it in place.
3. Cover the insulation with a house-wrap or face it with a vapor barrier.
4. Install a polyethylene vapor retarder, or equivalent material, over the dirt floor. Tape and seal all seams carefully. You may also cover the polyethylene with a thin layer of sand or concrete to protect it from damage. Do not cover the plastic with anything that could make holes in it, such as crushed gravel. Be sure the headroom of the crawl space meets local code regulations if you are considering pouring a concrete slab.
5. The orientation of the vapor barriers depends on the home's location or climate.