Photo by: Brain Pontolilo
This insulation can be used on walls, roofs, and foundations, and it is suitable for retrofits and new construction. All foam-insulation products are petroleum-derived, and most have a higher R-value per inch than fiberglass, cotton, or cellulose.
Rigid-foam sheets are sold in several thicknesses; most lumberyards carry sheets ranging from 1/2 in. to 2 in. thick. Thicker sheets (up to 6 in. thick) are usually available by special order. The installed cost of rigid insulation varies widely, depending on the project and location.
Rigid-foam insulation is a more effective air barrier than batts or blown-in insulation, especially if the seams between sheets are carefully sealed with caulk, canned spray foam, or tape.
Rigid foam is routinely used to insulate the interior or exterior of foundation walls. On above-grade walls, exterior foam improves the performance of a wall or insulated roof by reducing thermal bridging, improving air-tightness, and raising the R-value of the entire assembly. Be sure to install foam sheathing that is thick enough to keep the wall above the dew point.