It is important to insulate exterior walls because they can allow much heat gain on warm, sunny days. It is a waste of time and money to insulate under the flooring. No heat is lost in this area. R-value refers to the ability of a product to reduce heat, cold, and moisture in the home. All homes in the United States need basically the same kind of insulation.
Insulation is a material with the ability to store heat.
Two examples of insulation are fiberglass batting and rigid plastic board. Infiltration refers to the leakage of undesired air into the home. In the summer, insulation absorbs heat entering the structure from outside and helps prevent its infiltration into the living area. There are three basic areas of the home that can really benefit from the installation of insulation. The exterior wall area should be insulated as much heat can infiltrate here on warm, sunny days.