Local Knowledge About Rigid Insulation

Rigid insulation is made from fibrous materials or plastic foams and is pressed or extruded into boardlike forms. These provide thermal and acoustic insulation, added structural strength, and air sealing. Plastic foam board (or rigid foam) is the most expensive form of insulation and is made from polyurethane, polyisocyanurate, or polystyrene. It is commonly used in exterior walls (under the siding) and foundations. Since it provides a high R-value per inch of thickness, it is useful where a lot of insulation is desired in cramped quarters, such as cathedral or vaulted ceilings. Foam insulation must be covered with finishing material for fire safety.