As fuel prices keep skyrocketing, talk
keeps turning to ways of saving energy. The focus tends to be on
heating costs, but 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 on your house
and all sorts of other factors.
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 types can be used in unfinished walls, floors and
ceilings where the spacing is standard (studs or joists 16 inches or
25 inches on center), and where there are no obstructions such as
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
could probably benefit from more. Most U.S. homes should have between
R-22 and R-49 insulation in the attic, for example.
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 ground-up newspapers treated with boron to deter
rodents and insects and reduce the danger of fire. But don’t
over-insulate with this, since the weight of cellulose and the fact
that it will settle means it can cause drywall ceilings to sag.
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 conforms to
every nook and cranny, and offers a barrier to moisture. Rigid foam
insulation, commonly 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, dress
appropriately. 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.
Don’t do this: Don’t use unfaced fiberglass insulation to seal
air pockets, such as the spaces around plumbing and chimneys - the air
will only pass through it. To act as a sealant, insulation has to be
enclosed in something, such as a black or white plastic bag. The
latter is better because it decomposes more slowly.
