How To Insulate Bottom Of Floor Over Crawl Space

The sill plate is the first piece of framing lumber and it runs on top of the crawl space wall.

How to insulate bottom of floor over crawl space.

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. 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. Insulate the crawl space walls. Cut rigid foam pieces to size with the saw and attach the pieces to the inside crawl space walls with the latex adhesive.

However in a moist ventilated crawl space this insulation will eventually rot and become soaked with moisture. This will cause it to fall off the ceiling and on to the 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. Seal seams between the boards with the pvc tape.

When you re using fiberglass batting insulation material run it about 6 inches or so onto the crawl space floor. Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates. 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.

Aim for as few seams as possible by installing large sheets of foam. Use caulk or foam sealant to seal the joint between the top of the crawl space wall and the sill. 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. 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.

Fiberglass insulation on the floor joists in a crawl space will help keep the floor above warm. Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space.