COUNTRY SKILLS

Article Tools

Image Gallery

Print

E-mail

Comments

RSS

Insulating Walls

Heat energy radiates through hollow walls and is conducted through solid framing. The air between wall studs will develop convection currents that transfer heat from inner to outer wall. To stop all three processes, fill the wall with a nonconductive air-movement inhibitor—insulation—and face it with a radiation reflector or absorbent.

In new homes or renovations you can apply high-R-value rigid foam with an infacing foil backing over sheathing on exterior walls. But foam board is expensive; the most R-value for the buck comes from mineral-fiber insulation. In conventional frame walls with studs placed 16" in the center, stock insulation goes up quickly.

Roll insulation backed with a kraft paper or reflective foil-paper "vapor barrier" having staple flanges along the edges was once universal. But foil dulls, and paper is both an ineffective vapor barrier and flammable. Unbacked, semistiff frictionfit batts pose less fire potential, and you can see to fit them snugly. If using unbacked batts, wear a respirator.

Insulating our old home was a challenge, even with the interior walls torn off. It is framed with 6"-square studs spaced anywhere from one to two feet apart. Using R-19 Owens-Corning pink panther fiberglass, I had to cut batts 5 1/2"-thick and 15" wide to fit horizontally between studs.

I packed shreds of insulation loosely into odd spaces at the ceiling and floor so that the cavities would not leak heat. Expanding foam went into narrow spaces where I couldn't pack fiberglass easily without compressing, which squeezes out air and reduces insulation value.

The Vapor Barrier

To keep house moisture out of the insulation, I stapled six-millimeter, clear polyvinyl plastic sheet to the wall framing. This must be done immediately—especially if you don't plan to install wall paneling or drywall right away—because exposed fiberglass can shed tiny filaments that can cause lung problems.

To be effective, the barrier must form a contiguous, air-proof sheath around living space. I applied clear poly tape over staples and joints in the sheet. At the ceiling and floor, I caulked the seam between the floor and wall framing. Then I caulk-glued, stapled, and poly-taped edges of the sheet to beams.

You don't want to tear out perfectly good walls when insulating. Your best bet is to use blown-in insulation. Loose fiber glass, mineral wool, or cellulose recycled from newspaper and treated with fire retardants is blown through holes drilled through hollow walls of frame buildings. If applied uniformly, blown fiber adds R-3 or more per inch of thickness, giving you up to R-12 in a conventional 2 x 4 wall, or R-19 in a house framed with 6"-wide studs. Don't be tempted to rent a blower to pump insulation into your own walls. It takes an experienced pro to remove siding, drill through sheathing, pack insulation uniformly into all wall cavities, and then seal the outside so it won't leak air.

RSS | Comments | E-mail | Print