Sealing Air leaks—Getting the Most for the Money
Reducing air leakage makes for a more efficient and comfortable house. Reducing the leaks first that bring the biggest return on makes good business sense. A recent study reveals five places to prioritize that will save two air changes per hour at 50 Pascals for relatively little cost.
Air sealing recessed lights will save less than a quarter of an air change, but it is so simple and easy to do it achieves high returns on the costs of labor and materials. These lights are at the location of the highest air pressures in a house, so the relatively small gaps around them will pass significant amounts of warm air.
Duct boots cost about as much to seal as recessed lights and sealing them will reduce air leakage about as much as sealing the lights. Their location on the floor places them where the outside air pressure on a house is greatest to push cold air into the building. Together sealing these two areas will reduce air loss by about six tenths of an air change per hour.
Sealing the top plate to drywall connection will save about one full air change per hour when done properly. It costs more than sealing lighting and duct boots but is one of the most cost-effective measures and reduces air leakage more than any other method.
An often overlooked place to seal is the connection between the house and the garage. Attention to this space not only prevents air leakage, but keeps fumes and chemicals stored in the garage from getting into the house. Sealing here will only save about a tenth of an air change but the cost to do so is very low.
The fifth place to seal with the highest return on costs is the band joists. This will reduce air leakage by about one-half an air change per hour. It involves sealing between the joist and the sheathing, joist and plate, and between the sill plate, the joist and the foundation.
These five items done together will save about 2 air changes per hour at 50 Pascals. Assuming the plumbing, mechanical and electrical penetrations are sealed, it will reduce air loss more than sealing all the other locations combined and cost less to do it.