The Most Insulation Recommended in the Ceiling, Walls or Floor

Insulation Types

• Three standard types of insulation are used in houses: loose fill, blanket and foamboard. Loose fill is typically installed in attics, blown into hollows between joists with air pressure. Blanket is batts or rolls, typically placed between wall studs or attic joists. Foamboard is a rigid, plastic material often installed on outside components, but is sometimes used in interiors.

Loose Fill

• Loose fill is granules or pellets of cellulose, fiberglass, rock wool or cotton material. Cellulose is the most common. It is made from old paper, generally recycled newspapers, and treated with a fire-retardant chemical. Fiberglass is pellets formed from glass. Rock wool and cotton are both natural fibers that are treated with chemicals forming granules. Loose fill is commonly used in attics and hard-to-reach places, but is sometimes is put into wall cavities.

Fiberglass

• Blanket insulation is fiberglass, spun into thick sheets. Batts are sized to fit wall cavities, 15 or 16 inches wide and about 8 feet high. Rolls are unrolled in an attic and cut to fit spaces. Blankets are available in multiple thicknesses; 3 ½ inches is standard for walls, but other blankets may be 4-, 6- or 8-inches thick. It is available with a moisture barrier face or unfaced. Faced is used in walls and as original insulation in attics. Unfaced goes over existing loose fill or other insulation.

Rigid Foam

• Foamboard or rigid foam is made of some plastic, polystyrene, polyurethane or polyisocyanurate. It is made in thicknesses from about 1 inch to 4 or 6 inches, and offers high-insulating value for relatively little thickness. In interiors, it must be covered with gypsum board, plasterboard or other fire-resistant material. External applications require a weatherproof facing. Foamboard is typically installed outside of walls and covered with a house wrap.

R Values

• All insulation is rated with R value, which stands for resistance to heat. R values vary with the insulation type and thickness. Exterior walls generally require R values of 13 to 21, interior walls R 11. Ceiling and attic spaces require R30 to R38 because rising heat is most likely to escape through those areas. Floors are sometimes insulated when they are over an unheated basement or crawl space. Floors over heated basements or slab foundations are not usually insulated.