Next, air-seal your basement or crawl space. Seal all heating and cooling duct joints with fiberglass mesh and mastic (a pastelike sealant) or foil tape—but not duct tape. While you are at it, insulate these ducts if the basement or crawl space is not conditioned. Look for any holes (for example, around plumbing and electrical penetrations, drainpipes, and chimneys) that might allow air to move from this space into living spaces. Sealing at sill plate and rim joist areas is especially critical.
Only after you have done your work at the top and the bottom of your house should you think about addressing the more obvious air leaks in the middle areas of your home. Here, focus on sealing the larger gaps first. Infiltration into the middle part of your house is generally more obvious, but unless leaks are particularly large, they are also usually less significant than leaks in basements and attics. This is mainly due to the fact that leaks in the middle of your home are usually only a factor when the wind blows. However, the stack effect, which occurs most of the time, causes your home to lose heat even on calm winter days—and you only have to address the home’s roof or basement to effectively stop this heat loss.
You can usually find significant leakage areas easily on a windy day with a candle or a stick of incense. Walk around your house, holding the candle or incense stick close (but not too close) to walls, doors, and windows, and watch how the flame or smoke reacts. If the candle flickers or if the smoke from the incense stick swirls away from an area, you probably have a leak. You can also listen for leaks (they whistle), feel a cold stream of air, or look for daylight through cracks.
Once you have effectively air-sealed your home, consider adding insulation. If you’re retrofitting your home, begin at the top, go to the bottom, and then, if time and money permit, worry about the middle. New homes should be insulated to U.S. DOE-recommended levels or above. (For recommendations, visit the DOE’s Office of Energy Efficiency and Renewable Energy Web site at www.eere.energy.gov.)
Since it is both the most accessible and the most cost-effective area to insulate, the attic should be your first priority. Check with your state energy office for recommended levels of attic insulation. Don’t go by the local code requirements—they just stipulate minimum levels.
Once you have insulated the top and bottom of your house, you can think about adding insulation to your home’s exterior walls. Options include blowing in insulation through holes drilled in your home’s siding, or removing siding completely and adding foil-faced rigid polyurethane foam insulation. Unfortunately, this energy upgrade can be very pricey, so you may want to wait until your home needs new siding or extensive remodeling. Again, check with your state energy office or use the DOE’s online insulation calculator (www.ornl.gov/~roofs/zip/ziphome.html) for recommended insulation levels for exterior walls.