Insulation can lessen cooling costs

July 13, 2008|By Alan J. Heavens | Alan J. Heavens,McClatchy-Tribune

A well-insulated house in which air leaks are sealed means money saved on summer cooling costs, as well. What kind of insulation should you use? That depends.

First things first Insulation material has pockets of trapped air that prevent heat from penetrating it. How well the material resists heat transfer is known as its R-value. The higher the R-value, the better the resistance.

Need to know Some types of insulation are relatively simple for a do-it-yourselfer to install. Insulating blankets come as batts (precut pieces) or in rolls, and may have a paper or aluminum-foil facing that acts as a vapor retardant. Blankets are made of fiberglass (spun from molten sand and glass); rock wool, made of natural minerals; or slag wool, made from iron-ore blast-furnace slag, an industrial waste product. These can be used in unfinished walls, floors and ceilings where spacing is standard (studs or joists 16 inches or 25 inches on center), and where there are no obstructions (water pipes, electrical wires or gas lines).

Reflective insulation includes foil-faced paper, polyethylene bubbles, and plastic film. It, too, fits well between studs and joists in unfinished spaces; foil-faced polyethylene bubbles are most suitable for places with obstructions.

How much is enough? The U.S. Department of Energy suggests measuring the thickness of the insulation. If it's less than R-22 (7 inches of fiberglass or rock wool, or 6 inches of cellulose), you should probably use more.

Be sure to ask Would some other kind of insulation, such as varieties best installed by professionals, be better for your home? Blown-in insulation, for example - typically it's cellulose, a product made of newspapers treated with boron to deter rodents and insects and reduce the danger of fire.

Options, options Increasingly popular is foam insulation. It's typically made of polyurethane, has high R-values, doesn't shrink or settle once in place, blocks air infiltration because it fits in every nook and cranny, and offers a barrier to moisture. Rigid foam insulation, made from fiberglass, polystyrene or polyurethane, comes in a variety of thicknesses with insulating values of R-4 to R-8 per inch. Indoors, it has to be covered with 1/2-inch gypsum board or other building-code-approved material for fire safety.

What will it cost? R-19 fiberglass batts are running about 55 cents a square foot; R-38 batts are $1.10, judging from an extensive Internet search. Cellulose insulation is running 12 cents a square foot, uninstalled.

An ounce of prevention If you do the job yourself, wear a long-sleeved shirt and long pants, safety glasses and a mask. Fiberglass in the eye can be painful; inhaled fibers can give you a sore throat or worse.

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