10 Important Tips For Insulating Walls

Get the most energy efficiency from your insulation by filling all gaps, avoiding compression, sealing holes in framing and other expert tips.

Cut Fiberglass Batts to Exact Widths

It’s easy to insulate your walls with fiberglass insulation (at least when they’re open!),

but the job still requires attention to detail to get the maximum benefit. Every gap and compressed

batt leaves a path for heat or cold to escape.

Measure and cut the fiberglass batt for an exact fit. Add about 1/4 in. to the measurement

to ensure a snug fit. Use a 4- to 6-in.-wide board or strip of plywood as a straightedge to guide

your utility knife. Line up the edge of the board at the proper width, compress the insulation and

cut it with a sharp utility knife. A scrap of plywood under the batt will protect finished floors and

keep the blade from dulling on concrete.

Avoid Stuffing

Don't stuff full-width batts into spaces that are too narrow. Crumpling batts to fit narrow spaces

creates uninsulated air pockets. And packed insulation has a lower R-value.

Wear Protective Equipment

 Protect your skin, eyes, and lungs when you're working with fiberglass. Goggles, gloves, a dust mask, a cap, and long sleeve coverings protect you from fiberglass irritation. If you'r installing alot of it, consider wearing disposable coveralls.

Seal Narrow Gaps with Foam

Seal around window and door jambs with expanding spray foam. The main purpose of the spray
foam is to seal the space around the window to prevent air infiltration. Use foam that's labeled for window and door insulating. This "minimal-expanding" type reduces the chance of warping the jamb.
If there's still space around the window after the foam cures, lightly stuff the remaining space with strips of fiberglass insulation.

Notch Batts Around Electrical Boxes

Cut notches in batts to fit snuggly around electrical boxes. Airtight boxes have gaskets
that seal against the drywall. Put the batt in place, and use a scissors to snip around the box.
Tuck the snipped-out plug of insulation behind the box. Don’t wrap fiberglass batts around
electrical boxes or stuff full batts behind them.That creates gaps and air convection routes
around the box.

Split Batts Around Cables and Pipes

Split apart the batts to fit around wires and pipes to get the full value of the insulation.
Fiberglass batts have a vertical weave that allow you to easily tear it open for
insulating around electrical cables.

Avoid Stuffing Batts Behind Pipes and Cables

Don't tuck full-thickness batts behind pipes and cables. Compressing the fiberglass
decreases its insulating value and creates voids between the insulation and the drywall.

Plug Holes in Top and Bottom Plates

Plug holes in the top and bottom plates with expanding spray foam.
Even small holes can let a lot of air escape. Don't leave gaps around wires, pipes
or ducts unplugged. These gaps create pathways for warm interior air to leak into the attic,
wasting energy and causing attic condensation or even ice dams in cold climates.

Avoid Paper-Faced Insulation Where Possible

Don't buy paper-faced insulation for standard wall insulating jobs.
The paper facing makes cutting the batts difficult. And it's hard to create a tight vapor
retarder with paper-faced batts.

Buy Friction-Fit Batts

Buy unfaced friction-fit batts and seal the walls with a 4-mil poly vapor retarder.
Seal the gap between the bottom plate of the wall and the floor with acoustical sealant or caulk.
Press the poly into the sealant. Use special airtight electrical boxes (see photo, Tip 5)
or seal the poly to the electrical box with acoustical sealant.
Tape the seams in the poly withsheathing tape.