Insulation Materials for Common Walls

Fiberglass Blankets

• The most common type of wall insulation is fiberglass blankets. This typically is installed in batts, made specifically to fit into the cavities between wall studs. It is covered with a kraft paper facing as a moisture barrier. The facing is installed on the inside, facing the heated area, and is stapled to the studs on each side before the inside of the wall is covered. It is easily cut to fit around electrical outlets and other openings. Today batt joints are frequently sealed with special tape.

Loose Fill

• Loose fill is another type of wall insulation. This is cellulose made from old newspapers, fiberglass pellets or some fabric-derived material, such as rock wool or cotton. Loose fill is formed in granules or pellets and typically is sprayed into a cavity with air pressure. It is usually installed through an attic after the interior cladding of the wall is placed. It is good to fill hard to reach places.

Foamboard

• Foamboard is regularly used on exteriors of walls but also is sometimes used to insulate inside walls. Boards are made of polystyrene, polyurethane or polyisocyanurate (polyiso) shaped into rigid panels. Foamboard inside is used much like fiberglass batts, sized to fit wall cavities and cut to fit around electrical outlets and other impediments. Outside, it typically is nailed to exteriors before a house wrap and siding are applied.

Sprayed Foam

• Some walls have sprayed foam insulation. This is polyurethane, polyiso or some similar cementitious plastic applied in a liquid form which solidifies quickly. It is sold regularly in small spray cans and used to fill odd spaces, but also can be pressure-sprayed into new wall cavities, either open or closed. It is the least used wall insulation, except for small areas in conjunction with fiberglass or other insulation.

Other Blankets

• Fiberglass is not the only blanket type of wall insulation, although it is the most common. Rock wool and other natural fiber insulation, like cotton and some plastics, also can be formed into blankets and installed somewhat like fiberglass batts. Fiberglass is usually the choice, however, because it is inexpensive, readily available and easy to use.