Insulation Between Floor Joists In Crawl Space

When the basement or crawl space has vents installed insulating joist bays.

Insulation between floor joists in crawl space.

Floor insulation for moderate climes popular reads. It is important to secure insulation and cover it with a vapor barrier in order to prevent moisture and the mold that often follows close behind. If your space has them avoid adding insulation to the crawl space walls. In moderate or dry climates without the threat of sustained subfreezing temperatures insulation between floor joists makes sense.

This type of insulation allows for conditioned air to be introduced into the crawl space. Joist bays the open spaces between floor joists are prime hosts for insulation under specific circumstances. However the insulation needs to be treated with a fire retardant. Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space.

The fiberglass will also need to be secured in place using wire mesh twine wood laths or other securing methods which can be an intensive project that adds to the overall cost. Use caulk or foam sealant to seal the joint between the top of the crawl space wall and the sill. Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls. Don t compress the insulation as it requires its loft in order to maintain its rated r value.

This type of crawl space also allows insulation with an r value of 19 installed in the floor joist if the crawl space and has a permanently installed dehumidifier. Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates. Unlike fiberglass rigid foam insulation does not absorb water support mold or allow air to pass through providing that joints between boards are sealed with tape. The insulation should press right up against the floor between joists.

Gaps between the insulation and the floor can lead to inefficiency and heat loss. If the crawl space is ventilated which is ideal because it aids in the elimination of moisture then fiberglass insulation can be easily installed under the subfloor between the floor joists.