Insulation Between Floor Joists Over A Crawl Space

Moisture laden fiberglass becomes heavier and begins to sag and fall.

Insulation between floor joists over a crawl space.

Install an air and vapor barrier over the floor and tape it to the insulation. Instead install fiberglass batting between the joist bays which are the spaces between each set of floor joists. Stapling fiberglass batts between joists to the underside of your home s floor presents a number of problems. Joist bays the open spaces between floor joists are prime hosts for insulation under specific circumstances.

When the basement or crawl space has vents installed insulating joist bays. However the insulation needs to be treated with a fire retardant. Use caulk or foam sealant to seal the joint between the top of the crawl space wall and the sill. Floor insulation for moderate climes popular reads.

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. 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. In moderate or dry climates without the threat of sustained subfreezing temperatures insulation between floor joists makes sense.

Where winter temperatures are extreme opt for insulating the walls and sealing off the crawl space entirely. While this method does work in the very short term moisture eventually builds in the crawl space and grows on this highly porous surface. If your space has them avoid adding insulation to the crawl space walls. Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates.

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. Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls. 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.