How to seal drafts and replace weatherstripping
To seal drafts, find leaks at doors, windows, outlets, pipes and the attic hatch. Use weatherstripping on anything that moves, caulk for gaps up to 1/4 inch, and spray foam for gaps up to about 3 inches. If you have gas or oil appliances, get them tested, because sealing can pull exhaust back indoors.
When to seal drafts and check weatherstripping
ENERGY STAR gives no fixed schedule, so go by what you notice. A good time for a first pass is your first fall in the house, while you still feel every draft. Check door sweeps and weatherstripping again whenever a door lets in light or a room feels colder than its neighbors. ENERGY STAR says air sealing combined with insulation can save up to 10% on annual energy bills.
What to use to seal air leaks, by gap size
| Gap | Use |
|---|---|
| Moving parts such as doors and sashes | Weatherstripping: felt, rubber tape, reinforced foam, tension seal, bulb seal or a metal door sweep |
| Holes 1/4 inch or smaller | Caulk, such as acrylic latex |
| Gaps from 1/4 inch to 3 inches | Expanding spray foam |
| Plumbing gaps wider than 3 inches | Fiberglass backer first, then foam |
| Metal flues | Aluminum flashing and high-temperature caulk, best left to a pro |
You'll also want a caulk gun, a utility knife, a tape measure, and a dust mask and gloves for the attic.
How to seal drafts and replace weatherstripping
- Hunt for leaks on a windy day
Move a damp hand slowly around door frames, window trim, outlets and pipes under sinks. Check the attic hatch from below as well.
- Check for fuel-burning appliances
If a gas or oil appliance vents naturally, book combustion testing before you do more than basic door and window work.
- Fix the doors
Pull off flattened or cracked weatherstrip, clean the frame and fit new strips cut to length. Add a door sweep if you can see light under the door.
- Caulk the fixed gaps
Clean the joint and run one steady bead around window trim and where pipes and wires pass through walls.
- Foam the larger holes
Use expanding foam for gaps of 1/4 inch to 3 inches around plumbing. Keep it away from flues and anything hot.
- Seal the attic hatch
Stick weatherstrip around the frame so the hatch closes tight, and fix insulation to its top side. Look for dirty insulation nearby, which marks other leaks.
Drafts that point to bigger air sealing problems
Drafts are one symptom. These point to something bigger than a worn door seal:
- Ice dams on the roof in winter, which can mean attic leaks
- Cold floors, which can mean gaps in the basement or crawl space
- Dirty patches in attic insulation, where air has been filtering through
- Hot and cold rooms, or dust and odors coming from the attic, which can mean duct problems
- Insects or mice around walls and doors, since a gap that lets air in can let pests in too
How to seal drafts yourself, and when to call a pro
The Department of Energy says DIY works for obvious leaks around door frames and wall penetrations. It won't catch small hidden leaks, especially under attic insulation. An energy assessor finds those with a blower door test and an infrared camera.
Stop and call a pro in these cases:
- You have a gas or oil water heater or furnace that vents naturally. Tightening the house can make it back-draft exhaust gases indoors. ENERGY STAR advises having these appliances tested before and after sealing.
- You find vermiculite insulation in the attic. It may contain asbestos, so don't disturb it until an approved lab has tested it.
- You find knob-and-tube wiring from before about 1930. It can be a fire hazard when it touches insulation.
- You need to seal around a flue. Keep insulation at least 1 inch from metal flues and 2 inches from masonry chimneys, and never use spray foam there.
A tighter house can also trap radon, carbon monoxide and other pollutants, so it may need added ventilation. Keep your carbon monoxide alarms working.
Air sealing questions
How much can sealing air leaks save?
ENERGY STAR says air sealing and insulation together can save up to 10% on annual energy bills. Your result depends on how leaky the house is and your climate.
Can a house be sealed too tight?
Yes. A tight house can trap pollutants, and fuel-burning appliances can back-draft. ENERGY STAR advises having a home energy pro test for these problems, and a tight home may need mechanical ventilation.
Should I caulk or use spray foam?
It depends on the gap. ENERGY STAR's attic guide uses caulk for holes of 1/4 inch or less, and expanding foam from 1/4 inch to 3 inches. Don't use spray foam around flues.
What you’ll need
Sources: ENERGY STAR, U.S. Department of Energy
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.