Loose-fill insulation, which is poured or blown into attics or closed-up walls by machine, is manufactured from a variety of materials, including fiberglass, rock wool, cellulose, perlite, and vermiculite.

Some walls are filled with plastic foam. Polyurethane, which is sprayed on during construction, has an excellent R-value and blocks drafts caused by air infiltration. Urea-formaldehyde, an older type of spray foam, is no longer installed because of its potentially dangerous vapor emissions.

Rigid foam board insulation is also used during new construction; it's usually installed as roof or wall sheathing before the roofing or siding is applied. Reflective insulations, made from aluminum foil, are used mostly in hot climates for blocking radiant heat gain through roof and walls.

-- Tips courtesy of HomeAdvisor.com