Insulation Between Floor Joists In Crawl Space

Install an air and vapor barrier over the floor and tape it to the insulation.

Insulation between floor joists in crawl space.

Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls. In moderate or dry climates without the threat of sustained subfreezing temperatures insulation between floor joists makes sense. 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. Floor insulation for moderate climes popular reads.

Don t compress the insulation as it requires its loft in order to maintain its rated r value. 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. The insulation should press right up against the floor between joists. When the basement or crawl space has vents installed insulating joist bays.

If your space has them avoid adding insulation to the crawl space walls. 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. Instead install fiberglass batting between the joist bays which are the spaces between each set of floor joists. Joist bays the open spaces between floor joists are prime hosts for insulation under specific circumstances.

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. However the insulation needs to be treated with a fire retardant. Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates. Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space.

This type of insulation allows for conditioned air to be introduced into the crawl space. Use caulk or foam sealant to seal the joint between the top of the crawl space wall and the sill.