Page 100 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 80

Wall Insulation
Any time you remove interior wall finish, check the insulation. Walls in mild climates need R-13
insulation. That’s 3-1/2” of fiberglass, which fits perfectly in the cavity of a 2 x 4 stud wall. R-19 wall
insulation is appropriate in severely cold climates. But that requires a 6” wall cavity and 2 x 6 studs,
which may not be cost effective. If you need more than R-19 from an existing 2 x 4 stud wall, 1”
polyurethane sheathing can add R-6.

Adding insulation is easy when the wall cavity is open. When the cavity is closed, you can blow
cellulose insulation through a 1”-diameter hole cut in siding and sheathing. Open a hole at the top of
each stud space. Lower a plumb bob into the cavity to find where the fire block is installed. Then drill
another hole in the same cavity below the fire block. Blow cellulose into the stud space both above and
below the block. When the cavity is filled, patch entry holes with either plastic or wood plugs.

Floor Insulation
Houses with a furnace in the basement don't need insulation between the floor joists. Basements are
generally heated. But homes should have floor insulation equivalent to the wall insulation if the floors are
located above an unheated crawl space or any other unheated space. Fit insulation batts between the
floor joists. Hold the batts in place with wood or wire strips cut slightly longer than the joist space so
they spring into place (Figure 5-2). You could also staple wire netting under the floor joists to hold either
batt or blanket insulation tight against the underside of the floor sheathing. A vapor barrier has to be on
the top side of insulation placed between floor joists. That presents a problem when installing insulation
above a crawl space. Insulation manufacturers now offer roll insulation with inverse tabs so insulation
can be stapled between floor joists with the poly face-up against the floor sheathing.

Board Insulation
You can insulate brick, block and concrete walls by applying insulation board to the interior surface. The
thicker the board, the higher the R-value. Polystyrene insulated sheathing board has an R-value of 3.5
per inch of thickness. Polyurethane board carries a 6.25 rating per inch of thickness. Many types of
insulated sheathing can be installed over the existing siding. No tear-off is necessary, though additional
edge trim will be needed around windows and doors. If the owner wants 2” of foam insulation on a
basement wall, consider attaching 2” x 2” furring strips to the wall at 16” on center. Then install 2”
insulation board between the strips and hang drywall or other wall cover on the furring. Most insulation
boards, such as polystyrene, must be covered with drywall. They’re fragile, and won’t hold paint or
wallpaper. Also, most insulation boards aren’t fire-resistant. Fire codes require that interior wall surfaces
be covered with fire-resistant material, such as drywall.