Roof & Wall Insulating Coatings

Loose Fill

• Loose fill is a standard type for attics and open wall cavities. The most common material is cellulose, made from old newspapers shredded and treated with a fire retardant chemical. It is granular and is installed with air hoses, sprayed into attics and wall cavities. It has an R value, or heat resistance, of 3.5 per inch. Fiberglass pellets, rock wool and cotton are other types of loose fill, also blown in, but with somewhat lower R values.

Blankets

• Blankets are mainly fiberglass, which are glass fibers spun into thick sheets. Fiberglass batts, which are one type of blanket, are standard wall insulation, cut to fit between studs and faced with a kraft paper vapor barrier. Fiberglass has an R value of starting at 3.2 per inch, and reaches 4 for high density versions. Wool and cotton, sometimes recycled denim, also are formed into batts and have R values comparable to fiberglass, but are not as easy to install and are not available in all areas. Blankets are used in both walls and attics.

Rigid Foam

• Rigid foam is polystyrene, polyurethane or polyisocyanurate--polyiso--formed into solid panels, from 1 inch to about 6 inches thick. Polyiso has a high R value, usually 6 or 7, but is the most expensive. Extruded polystyrene, or XPS, is commonly installed on the outside of house walls and on roof decking before shingles are added. It has an R value of about 5, but seams must be taped to seal them. Rigid foam can be used inside wall cavities or in attics, but its rigid nature makes it harder to install there.

Sprayed Foam

• Sprayed foam is usually some type of polyurethane, which is sprayed as a liquid that expands to fill cavities and then solidifies. It is most frequently used in spray cans in conjunction with other insulation to seal small and hard-to-reach cavities or fill irregularly-shaped spaces that are hard to insulate with other materials. It can be sprayed into wall cavities with high pressure hoses, but requires a professional.

Vapor Barrier

• All insulation should be installed over a vapor barrier to block moisture. Most types degrade when wet. Vapor barriers are installed facing toward the heated area of a house, for instance, with kraft paper backing on the inside of the wall. Most insulation also should be shielded from sources of direct heat, like chimneys and heating vents. Rock wool can be installed near such heated areas.