Seal Foam With Foam - Basement or crawl space rim joists are a major source of energy loss in a house, so it's well worth the effort to add insulation and seal any cracks and gaps. A good DIY approach is to cut rigid foam insulation to fit between the joists. Cut it about 1/2 in. undersized so it's easy to fit in. Shim the rigid foam in place with little chunks of foam. Then fill the space around it with expanding foam. Don't forget to caulk or foam the joint between the sill plate and the f...
