How to Seal Air Leaks Around Windows and Doors in Your Home

Knowing how to seal air leaks is one of the cheapest ways to make your home more comfortable. Small gaps around windows, doors and pipes let conditioned air escape. Together, they can equal a hole the size of a window. Sealing them can reduce energy costs by 10 to 20 percent, according to the U.S. Department of Energy.

You can read its full advice on Energy Saver website.

Find Air Leaks in Your Home

Before you seal, locate the leaks. Try these simple tests.

• Hand test: move your hand slowly around windows, doors and outlets on a windy day.
• Incense or candle test: hold a lit stick of incense near edges. Smoke that wavers or blows sideways shows a leak. Keep flames away from curtains.
• Light test: close a door at night and shine a flashlight around the edge from outside. Light that shows through marks a gap.
• Visual check: look for cracked caulk, loose trim or gaps in siding.

Common Places Air Leaks Hide

• Window and door frames
• Electrical outlets and switches on exterior walls
• Attic hatches and recessed lights
• Where pipes and wires enter the house
• Dryer vents and exhaust fans
• Fireplace dampers
• Basement rim joists

Supplies You Need

• Exterior-grade and interior caulk
• Caulk gun
• Weatherstripping tape or door sweeps
• Expanding spray foam for larger gaps
• Foam outlet gaskets
• Putty knife and utility knife

How to Seal Air Leaks Step by Step

1. Seal Windows With Caulk

Remove old, cracked caulk with a utility knife. Clean the surface and let it dry. Then apply a smooth bead along the gap. Smooth it with a wet finger or caulk tool. Use caulk for gaps smaller than a quarter inch.

2. Add Weatherstripping to Doors

Press adhesive weatherstripping around the door frame so the door compresses it when closed. Then install a door sweep along the bottom to block drafts.

3. Insulate Outlets and Switches

Turn off the power at the breaker. Remove the cover plate and place a foam gasket behind it. Then replace the plate.

4. Fill Large Gaps With Foam

Use low-expansion spray foam to fill gaps around pipes and wires. Trim excess once it cures. Avoid using it near heat sources.

5. Seal the Attic Hatch and Ducts

Add weatherstripping to the attic hatch. Seal visible duct joints with foil tape or mastic. For more details, see our guide on how to insulate an attic.

6. Consider Window Film

For older windows, apply clear window insulation film in winter. It creates a barrier that reduces drafts.

Do Not Seal Everything

Gas appliances, fireplaces and furnaces need fresh air to run safely. Do not block combustion air vents. If you have concerns, consult an HVAC professional.

Next Steps to Save Energy

Pair sealing with a new filter and good thermostat settings. Check how often to change your air filter, and follow our tips to lower your electric bill.

Final Thoughts

You can seal air leaks in a single afternoon with low-cost materials. Find the gaps, apply caulk and weatherstripping, and add foam where needed. You will enjoy fewer drafts and lower bills.