How to Find and Seal Air Leaks in Your Home
Last updated March 2015
Before deciding to have an audit, a good step is to find and plug air leaks—holes, cracks, and gaps that let cold air in and warm air out in the winter—and do the reverse in the summer. If you feel drafts during winter, that’s an obvious sign of leaks. If you consistently feel chilled between furnace cycles, that’s another sign.
One little leak might not seem much, but the cumulative effect of several leaks can amount to the equivalent of leaving open a small window. If you have a lot of leaks, they will dramatically decrease the value of any installation you add.
MassSave, a program offered by utilities operating in Massachusetts, at the time of this writing is offering rebates that pay 75 percent of insulation costs (with a maximum rebate of $2,000) and all costs of air-sealing projects. To qualify for MassSave’s rebates, you first have to contact a program-approved contractor to perform an energy audit and preparation of a list of recommended improvement projects. The audit is free, and you can access a list of approved contractors at MassSave or by calling 866-527-7283.
You can track down major air leaks on your own by taking the following steps: (1) Turn off your furnace on a cool, very windy day; (2) Shut all windows and doors; (3) Turn on all exhaust fans that blow air outside, such as bathroom fans or stove vents; (4) Light an incense stick and move around your house; where smoke is blown, there’s a draft. Focus on inspecting areas where different materials meet—brick and wood siding, foundation and walls, and between the chimney and siding. Other common problem areas—
- Door and window frames
- Mail slots
- Points of entry for electrical and gas lines, cable/satellite TV wiring, and phone lines
- Outdoor water faucets
- Where vents pass through walls
- Cracks or gaps in siding, stucco, masonry, all foundation materials
- Around window air-conditioning units
Cracks or gaps measuring less than 1/4 inch wide can be sealed with caulk. For larger cracks, use a polyurethane foam sealant. Weatherstripping can be used to minimize leakage around doors and windows. Open-cell foams are inexpensive and relatively inefficient but easy to apply and suitable for low-traffic areas. Vinyl is more expensive and lasts longer. Metals last for years and provide a decorative element for older homes. Choose according to location, function, and looks.
The free basic energy audit offered through MassSave should identify even more leaks, which can be sealed for free if you use a program-approved contractor. If you want a full energy audit, you must hire your own auditor. Full audits cost $300 to $500 for an average-size home. Larger homes with more than one heating unit cost more.
Before paying for an audit, confirm that the auditor will use a calibrated blower door to measure the overall air leakage of your home, and make sure it performs a thermographic inspection using an infrared camera.
Also, if you’re paying for the audit, hire one certified by nonprofit Residential Energy Services Network (Resnet). Certified auditors must complete Resnet’s training program and carry a minimum of $500,000 in liability insurance.
Whatever other work you have done, be sure to have exposed ductwork checked for holes or gaps, and then seal them with duct tape. Leaky ducts can waste 20 percent or more of your home heating energy bill.