Concentration of CO2 in the Atmosphere

DIY Energy Upgrades: Attics

Image: U.S. EPA

Dave Keefe

Attics are often miserable places. They’re cramped and dark, dusty and dirty. They’re hard to get into and hard to get out of. Most of the time they are either too hot or too cold. There’s usually nothing to stand on, even if there is room to stand, which there often isn’t. Often there isn’t even room to sit, even if there is something to sit on, which there isn’t. If you step in the wrong place you fall through. The air quality is awful. There’s a bunch of old nasty insulation in the way. There are hornets up there. And mice and bats. And the feces thereof.

This series of articles is about doing it yourself. As energy upgrades go, tackling your attic is a challenge to do right. Mind you, it’s not as challenging to do it badly, and lots of people, both homeowners and pros, do that. But you shouldn’t.

Insulating your attic isn’t really about insulation. It’s about air sealing. Your typical attic floor has lots of air leaks in it. Tops of the walls, electrical penetrations, around the chimney, plumbing vent stack, ceiling light fixtures, exhaust fan, hatch, etc. Warm air migrates to your attic all winter long through these leaks. Sealing them is more important and more cost-effective than installing insulation. Adding insulation without air sealing is probably doing more harm than good. It makes any further attempt at air sealing harder, more expensive, and less likely to happen. If anyone wants to add insulation to your attic without doing the air sealing, you shouldn’t let them, whether they are pros, well-meaning friends, or you yourself.

When warm air rises into the attic, it takes household moisture with it. This is the main reason for moisture problems in cold-climate attics. The moisture comes from the house. The best way to prevent your roof from rotting is to keep the house air in the house.

If you have bathroom exhaust fans in the attic floor, make sure the ducting is good (smooth-walled pipe, airtight, minimum angles, insulated). If the fan is old or noisy it’s a good idea to replace it before you do the attic work, since it will be harder and more expensive after everything is buried in the new insulation.

Chimneys need clearance to combust materials. They often have big air leaks around them, so they first need a horizontal layer of metal sealed to the chimney and to the surrounding framing so that the chase around the chimney is closed off at the level of the attic floor. Don’t install any combustible insulation too close to the chimney. Masonry chimneys should have three inches of clearance.

If you have older recessed lights, it may be unsafe to seal and insulate them. If they are not Insulation Contact (IC)-rated, you should replace them with LEDs.

The area at the bottom edge of the roof where the roof comes down close to the exterior wall (the eave) is hard to get to. This is often done badly. It’s best to provide a thin vertical barrier above the OUTSIDE EDGE of the wall to get good coverage over the top plate. You should air-seal the top plate of the wall also. This is a pain to do.

We have lots of houses that could use an attic upgrade, but it’s harder to do correctly than most people think. And it’s better to not do it (yet) than to do it badly. If you’ve read this far and haven’t been scared off, maybe you have enough determination to do it. You’ll need more info than I can provide here, so do your homework. Or you can work with a contractor who knows what he or she is doing, use your sweat equity for set-up, clean-up, and the parts you might be good at, and let the pros get down and dirty for the rest.

Dave Keefe is a fifth-generation Vermonter who has worked for over 35 years as a contractor, consultant and teacher to improve the performance of existing homes.

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