Sealing air leaks can reduce heating and cooling energy costs, enhance a building's durability, and contribute to a healthier, more comfortable indoor environment—and save money quickly.
Find it! Sealing products
Locating the air leaks in your home is essential before deciding how to effectively seal them, as suitable products and solutions vary widely depending on the size and location of each air leak.
How to seal air leaks
- First, you must locate the leakage sites in your home. A professional contractor or certified Home Energy Rater can conduct a blower door test which will pinpoint problem areas in your building shell.
- You can also identify leaks yourself using the following tips. See ENERGY STAR's Do-It-Yourself Guide to Home Sealing for in-depth instructions.
- Start in the attic or basement, looking for plainly visible holes, dirty patches of insulation, or cracks and seams along kneewalls and around fixtures, hatches, and ductwork. The nonprofit Urban Options offers a convenient online weatherization checklist to help keep track of both problem areas and the materials needed to seal them.
- To locate the sources of minor leaks and drafts, hold a lit stick of incense or piece of string near windows, doors, skylights, baseboards, outlets, fireplaces, and other possible leakage sites throughout your home's interior; if the smoke blows horizontally, then there is an air leak nearby. This testing method is most effective when a home has first been pressurized by using exhaust fans or window fans to suck air out of rooms, thereby increasing infiltration of outside air (be sure to first turn off all combustion appliances to protect against backdrafting).
- Seal all air leaks using caulk, weatherstripping, insulating spray foam, plastic sheeting, or other materials where appropriate. Air sealing in attics with no ventilation system or around ducts and complex recessed lighting fixtures may require professional assistance to facilitate compliance with safety standards.
- Always ensure that adequate ventilation systems or strategies are in place to prevent moisture accumulation and mold growth.
- Consider increasing attic — to further improve energy efficiency and home comfort.
Sealing air leaks helps you go green because…
- It reduces both heat loss and heat gain through the building shell, conserving energy and cutting associated costs.
- It improves physical comfort levels within the home by helping to maintain more consistent interior temperatures and eliminating drafts.
- It may enhance air quality by helping to seal out unconditioned exterior air, which may contain dust, allergens, insects, and other impurities.
- It helps maximize both the durability and the efficiency performance of other energy-saving systems like insulation and low-E windows, and can enable the purchase of smaller, more efficient HVAC cooling units.
The US Department of Energy (DOE) estimates that air leakage adds approximately 10 percent to the average homeowner's energy bill,, accounting for 30 percent or more of the costs associated with heating and cooling. Between 50 and 70 percent of the energy used in an average American home is consumed by heating and cooling systems. Although there are numerous factors to consider when seeking to maximize a home's energy efficiency (see the DOE's whole-house approach), the DOE lists air sealing as a top priority because unsealed leaks can significantly undermine other energy-saving improvements to a building's shell or HVAC equipment. Reducing infiltration means reducing the workload for heating and cooling units, in turn lowering pollution levels: the Rocky Mountain Institute estimates that sealing large air leaks in the typical American home will reduce that home's CO2 emissions by 1,300 pounds per year.
Where should I start?
Despite the urgency that many homeowners place upon eliminating drafts around doors and windows, the most significant air leaks are usually in a home's attic and basement. Hot air tends to rise and escape through the attic, allowing cold air to rush in through leaky basements, walls, windows, skylights, and doors to take its place. The Department of Energy recommends starting at these major leakage sites before moving on to caulking and weatherstripping around drafty doors, walls, and windows. If your home employs ducts to distribute conditioned air, sealing them with duck mastic can substantially reduce the 20-30 percent of air typically lost through leaky ductwork.
How much will it cost?
Often listed as the most cost-effective energy efficiency upgrade available, sealing air leaks generally range from $100-$600 per house, depending on whether homeowners choose to make the improvements themselves or hire a professional.
Subsidies and incentives
In the US, sealing air leaks in your home may qualify you for tax incentives at the federal, state, or local levels. For detailed information, see these resources:
- American Council for an Energy-Efficiency Economy Updates on potential energy legislation.
- Tax Incentives Assistance Project Explains federal tax credits for energy efficiency.
- Alliance to Save Energy Offers an index of energy efficiency programs by state.
- Database of State Incentives for Renewables & Efficiency Provides information on state and federal incentives.
- Contact your utility provider for information on local offers.
Related health issues
Ensuring adequate ventilation and air flow is essential to preventing moisture buildup and mold growth when sealing a home against infiltration. Providing for natural air flow is especially important in the attic to prevent ice-damming in the winter and allow proper circulation in the summer.
- blower door test: A test conducted by home energy auditors to pressurize a building and reveal air leaks.
- caulk (or caulking): A sealing compound used to fill seams and patch small air leaks.
- kneewall: A small wall connecting attic floor joists to a sloped roof; often covered with sheathing to enclose an attic space.
- weatherstripping: A material applied to the gaps around windows and doors in order to seal them against air leakage.
- US Environmental Protection Agency - Indoor Air Quality
- EERE Consumer's Guide - Caulking
- EERE Consumer's Guide - Weatherstripping
- Lawrence Berkeley Labs - Home Energy Saver
- US Department of Energy - Technology Fact Sheet: Air Sealing
- Rocky Mountain Institute - Home Energy Brief #1: Building Envelope
- Energybuilder.com - Home Weatherization
- ENERGY STAR - A Do-It-Yourself Guide to ENERGY STAR Home Sealing
- ENERGY STAR - Air Seal and Insulate with ENERGY STAR Home Sealing
- Alliance to Save Energy - No-Cost Low-Cost Tips for Saving Money & Energy
- ENERGY STAR - Increased Insulation: Building Envelope Improvements
- Rocky Mountain Institute - Cool Citizens: Everyday Solutions to Climate Change
- EERE Energy Savers - Sealing Air Leaks
- US Department of Energy - Insulation Fact Sheet
- Department of Energy - Technology Fact Sheet: Air Sealing
- ENERGY STAR - Home Ready Checklist
- US Department of Energy - Technology Fact Sheet: Ceilings and Attics
- EERE Consumer's Guide - Glossary of Energy-Related Terms