Basements
Closed-cell spray polyurethane foam (SPF) is the best insulation for this application. SPF insulation stops the diffusion of moisture from the damp concrete to the interior of the basement.
If your basement has stone-and-mortar walls, you can’t insulate them with rigid foam. The only type of insulation that makes sense for stone-and-mortar walls is closed-cell SPF Insulation, due to its ability to enter into cracks and crevices.
If you plan to insulate your basement walls with spray foam, the best approach is to frame your 2×4 walls before the foam is sprayed, leaving a gap of 1-1/2 in. to 2 in. between the back of the studs and the concrete wall. The gap will be filled later with spray foam.
Rim Joists
Closed cell SPF insulation out performs any insulation that can be installed for insulating rim joists. Closed cell SPF is an effective thermal, air, moisture and vapor barrier. The rim joist (piece of wood) is the part of the floor framing that sits on the basement foundation walls. This is where the foundation and the first floor met at ground level. Using SPF insulation on the rim joist is the best way to improve a home’s energy efficiency and comfort. When the rim joist is uninsulated, only the rim joist (piece of wood) prevents the intrusion of hot and cold air. Allergens, dust, pests, dust mites, mold spores and pollen can also enter a home here through cracks and crevices. As SPF is applied, it expands to seal cracks and gaps, preventing condensation from forming on the rim joist and protecting the home from mold and rot that can result from condensation. When properly applied to the rim joist at a thickness of one inch or more, SPF insulation prevents air leakage that creates drafty conditions and reduces energy efficiency.
Please be advised! It is required that an ignition/thermal barrier be applied or installed on any spray polyurethane foam insulation. Please read the information provided on this website about Thermal & Ignition Barriers. Check with your local code enforcement offices about any codes that must be followed in regards to thermal and ignition barriers when installing spray polyurethane foam insulation.