How to Install Batt Insulation in Crawl-Space Walls

Seal any areas that have holes or gaps to the outside. Use the caulk to seal these areas. Cut the tip of the caulk tube 1/8 of an inch from its end at a slight angle with the utility knife. Set the caulk into the caulk gun and twist the L-shaped bar at its end up against the bottom of the caulk. It might take a couple of pulls on the trigger to get the caulk started. Once started, hold even pressure on the trigger as you seal any cracks or holes with caulk.

Measure the length of the cavities requiring the installation of insulation. Because you are working in a crawl space, you might not have enough room to cut and fit the batts individually, so measuring and cutting the batts beforehand will make the process go quicker.

Cut the insulation batts based upon the measurements. Never cut down the width of the insulation, as the insulation is purchased based upon the width between studs. Manufacturers produce batts of varying widths based on typical construction stud placement. Hold the insulation with one hand and cut with the other the length needed for the space. Insulation is easy to cut; try avoiding squeezing it while you cut in.

Set the insulation into the place between studs. Tuck the insulation corners in carefully, keeping the face of the insulation smooth. Run a gloved hand over the insulation to smooth out any wrinkles. The insulation will take on the appearance of a thick-blanketed tucked-in bed if installed correctly.

Repeat the process for the entire crawl space.

Add a vapor barrier over the insulation after installed. This helps prevent moisture control. While insulation resists heat flow, it doesn’t resist airflow. The vapor barrier retards not only air flow but also air heavy with moisture, as well. Cut the vapor barrier to fit across the studs in the crawl space and staple in place. Don't pull it tight, but ensure it is smooth as you staple it in place.