Pouring wool also can be used to insulate an attic floor. The insulation is simply poured out of a bag, then leveled with a rake or a short piece of board.

To insulate a wall, fit the end of a blanket snugly against the top piece of framing. Working down, staple the flanges to the sides or the faces of the studs. (With aluminum foil-faced blankets, staple to the sides to create an air space, which is necessary for the heat-reflective value of the foil to be achieved.) Space the staples about 8 inches apart. Cut the blanket to fit tightly against the framing at the bottom. If more than one piece of blanket is used in the same stud space, butt the ends tightly together. The vapor barrier must face the side of the wall that is heated in winter.

To insulate stud spaces that are narrower than normal, cut the insulation about 1 inch wider than the space to be filled. Staple the remaining flange, then pull the vapor barrier on the other side to its stud and staple through the barrier.

Walls can be insulated with unfaced blankets and a separate vapor barrier, either 2-mil-or-thicker polyethylene sheeting or foil-backed gypsum board. Keep polyethylene taut as you apply it. Staple it in place.

Install insulation behind pipes and ducts (to keep them warm) and behind electrical boxes. Spaces of this sort also may be hand-packed with loose wool. To get loose wool, pull pieces from a blanket.

Cracks and very narrow spaces, such as those around window framing, should be stuffed by hand with loose wool and covered with a vapor barrier.

Masonry walls, basement walls and the like, are insulated by first fastening 1x2, 2x2, or 2x4 furring strips in place vertically. They should be placed 16 or 24 inches from the center of one strip to the center of the next.

With 1x2 furring, use special "masonry wall" blanket insulation (an unfaced material, of about an R-3 rating, which should be covered with polyethylene or foil-backed gypsum board to provide a vapor barrier). With 2x2s or 2x4s, install R-7 or R-11 blanket insulation as in any other wall.

To insulate floors above cold spaces, push the batts or blankets between the floor joists from below, vapor barriers up. To support the insulation, lace wire back and forth among nails spaced about 2 feet apart in the bottoms of the joists. Pieces of blanket cut to size should be fitted, vapor barriers in, along the sill at the ends of the floor area.

FIGURING HOW MUCH
INSULATION YOU'LL NEED

First, calculate the overall area to be coveredmultiply the length by the width. Then adjust this number to allow for the area taken up by joists or studs. If joists or studs are 16 inches apart, multiply. by .90. If they are 24 inches apart, multiply by .94. The answer is the number of square feet of insulation you'll need.

Mineral wool blankets and batts are available to fit 16-, 20-, and 24-inch joist and stud spacing.

If you're going to use pouring wool in an attic floor, usually there will be a bag label that will tell you how many square feet a bag of that particular insulation you'll need for a desired R-number and thickness. Divide that number into the number of square feet you want to cover, and you'll know how many bags to buy. (See the sample label for loose-fill insulation, Page 19.)

TOOLS TO DO THE JOB RIGHT

Sharp knife to cut blankets and batts. A serrated-edge kitchen knife works well.

Straight edge to cut along-a rigid metal rule or a short length of board.

Measuring tape if you don't use a metal rule as a straight edge.

Rake, or other tool, to push or pull blankets to the eaves edge if there isn't much headroom.

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Walk boards-several pieces of 3/4 inch utility-grade plywood, 12 to 16 inches wide and 4 feet long, or something similar. If you step on the top ceiling surface, your foot will plunge right through-so use walk boards.

Portable light, such as a mechanic's trouble light or a clamp-on photographic light. An extension cord, too. Staple gun for applying wall insulation. It can be rented.

PRECAUTIONS TO TAKE

Treat electrical wiring with care. Don't try to pull it or bend it out of the way.

Even in the cleanest of homes, attics tend to be dusty. Wear old clothes.

Insulations fibers can cause temporary skin irritation, so wear work gloves and loose-fitting clothes, including a long-sleeved shirt.

Be wary of nails that stick through the roof sheathing above your head.

Don't smoke in the attic.

DO'S AND DON'TS TO DO IT RIGHT

DO put the vapor barrier side of insulation blankets and batts down in the ceiling-even if, when adding new insulation on top of old, you've slashed the barrier to let moisture vapor pass through.

DO insulate under attic walkways, pulling or pushing the insulation as needed. If much of the area is

covered with flooring, you might need to remove some boards for access to the space.