When attic, walls or floors are under-insulated, a large part of your energy costs for heating or cooling may be heading straight for the great outdoors.

Insulation retards heat in its natural quest to move from a warmer to a cooler space. In the winter, when warm room air exits through walls, rises up through the attic and roof, and flows down through the floor, insulation blocks or at least slows its departure. And in the summer, when warm outdoor temperatures try to force their way into your air-conditioned rooms, insulation holds the heat at bay.

Several types of insulation are available. Batts and blankets of fiberglass or rock wool insulation are affordable and easily installed in open framing.

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