In a heated crawlspace or one with uninsulated ducts or water pipes, the walls should be insulated to keep the space warm so pipes and ducts experience less energy loss. Use unfaced fiber glass insulation for the installation:
- Measure and cut small pieces of insulation and fit them snugly into the band joist.
- At a minimum, cut the insulation long enough to completely cover the crawlspace wall—even better is to carry the insulation out onto the ground by two feet or more.
- Use long furring strips and standard nails, or use cap nails to attach the insulation to the wood plate at the top of the foundation wall.
- When attaching the insulation try to minimize any compression by only driving the nails part way into the plate.
- After the insulation has been installed, a 4- or 6-mil polyethylene vapor retarder should be spread across the entire floor and under the insulation. Place rocks or bricks around the perimeter to hold it in place.