How To Insulate Bottom Of Floor Over Crawl Space

Use caulk or foam sealant to seal the joint between the top of the crawl space wall and the sill.

How to insulate bottom of floor over crawl space.

Aim for as few seams as possible by installing large sheets of foam. It will also help to stop that echo that can be heard when you walk on the floors suspended over a crawl space. Cut pieces of insulation just large enough to fit along the rim joist the framing material into which all the floor joists are nailed. This will cause it to fall off the ceiling and on to the floor.

Applying spray foam to the dirt floor of your crawlspace may be one of the easiest and most effective solutions and if so then you would be best not to insulate the joists over your head and just heat that space instead. This will give you the thermal barrier between the crawl space and your living space as well as help keep the air from getting from the crawl space into the living space. You could also use batt insulation but don t. 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.

Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates. To insulate the crawl space i would use a closed cell two pound 907 gram spray foam because it will act as both your vapour barrier and insulation. Fiberglass insulation on the floor joists in a crawl space will help keep the floor above warm. However in a moist ventilated crawl space this insulation will eventually rot and become soaked with moisture.

The sill plate is the first piece of framing lumber and it runs on top of the crawl space wall. When you re using fiberglass batting insulation material run it about 6 inches or so onto the crawl space floor. 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. If you would like to keep your crawl space vented because you live in a low humidity environment we recommend insulating the crawl space floor with fiberglass or rock wool mixed with spray foam for air sealing.

Cut rigid foam pieces to size with the saw and attach the pieces to the inside crawl space walls with the latex adhesive. Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space.