Insulting Floor Joist Crawl Space

The old fashioned way of insulating a crawl space was to install fiberglass batt insulation between the exposed joists in the crawl space.

Insulting floor joist crawl space.

In those days common building practice was to insulate the floor above the crawl space and to leave the crawl space s wall vents open so any moisture buildup would vent to the outside a. This type of insulation allows for conditioned air to be introduced into the crawl space. Using the wrong kind of crawl space insulation can actually increase the likelihood that mold and mildew will grow in the dark damp crawl space. 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.

Be sure to wear a long sleeved shirt gloves eye protection and a dust mask when handling the itchy stuff. Unless there are excessive moisture problems in the crawl space use unfaced fiberglass batts to insulate the walls. A crawl space under a house helps protect against certain pests but a crawl space with abundant moisture can invite problems including mold wood rot and vermin. 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.

Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space. Foam not fiberglass is the right choice. While this method does work in the very short term moisture eventually builds in the crawl space and grows on this highly porous surface. Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates.

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. Crawl space insulation basics. Stapling fiberglass batts between joists to the underside of your home s floor presents a number of problems. Use closed cell spray foam to insulate the rim aka band or perimeter joists the joist that rests on top of your foundation walls.

However the insulation needs to be treated with a fire retardant. Glue rigid foam insulation board to the inside of foundation walls using waterproof construction adhesive and seal all seams with waterproof tape.