Drafty doors and windows: caulk the gaps that stay put, weatherstrip the parts that move

Find the leaks first

DOE says to check around walls, ceilings, windows, doors, light and plumbing fixtures, switches and outlets. Look for gaps, caulk or weatherstripping that was put on badly, and doors and windows that don’t close tightly. [S2]

• Smoke test. On a windy day, DOE says to carefully hold a lit incense stick or a smoke pen next to windows, doors, outlets, fixtures and the attic hatch. If the smoke travels sideways, you’ve found a leak. [S2] [S5]
• No flame needed. Virginia Cooperative Extension tapes tissue paper to a dowel and moves it around the same spots. Then it repeats the check with the kitchen or bath exhaust fan running, if the fan vents outside. [S8]
• Paper or dollar bill test. Close a window or door on a sheet of paper or a dollar bill. If it slides out easily, ENERGY STAR and the Extension say the weatherstripping needs to be thicker, repaired or replaced. [S5] [S8]
• Flashlight test for doors. At night, with the lights off, one person moves a flashlight around the edge of the closed door from outside. If a helper inside sees light, the door needs weatherstripping. [S8]
• Look outside too. Check around window frames for caulk that has cracked or peeled. [S8]

Caulk what stays put, weatherstrip what moves

DOE draws the line clearly. Caulk goes in cracks and openings between parts that don’t move, like the seam where a door or window frame meets the wall. Weatherstripping seals the parts that do move: doors and windows that open. [S1]

Caulk is for narrow gaps. ENERGY STAR and Virginia Cooperative Extension both put the limit at about 1/4 inch. The Extension says aerosol foam sealants generally handle holes up to 1/2 inch, and that bigger gaps need foam backing before you caulk. [S5] [S8]

• Clean and dry. Apply caulk to a clean, dry surface in one continuous bead, and fill the gap completely, the Extension says. ENERGY STAR adds: clean out the crack first and smooth the bead. [S5] [S8]
• Backer rod, gently. Press it in slightly below the surface. ENERGY STAR warns not to force it so hard that the frame bends, which can make a window or door stick. [S5]
• Low-expansion foam around frames. DOE and ENERGY STAR call for low-expansion or non-expanding foam made for windows and doors between the frame and the wall framing. [S1] [S5]

Gap check

Pick the gap you’re looking at to see what the sources say goes in it.

Not sure of the width? Measure it. The cutoffs in the sources are 1/4 inch for caulk and 1/2 inch for aerosol foam; anything wider gets backing first. [S5] [S8]

Doors: three sides and the bottom

Gaps add up fast. The Extension says a pair of 6 foot 8 inch doors with no weatherstripping can easily leave a 1/4 inch gap where they meet. That’s about a 20-square-inch opening to the outside. [S8]

• Top and both sides. Put the weatherstripping on the jamb so it seals against the face of the closed door along the top and both sides. [S8]
• The bottom. A door sweep, a metal strip usually with a flexible edge, suits a door with no threshold. A gasket threshold replaces the old one but wears quickly in busy doorways. A door shoe fits any threshold that isn’t worn in the middle. [S3] [S8]
• Most-used doors. The Extension suggests the more permanent kinds of weatherstripping there. Done right, the door should still open easily and seal when shut. [S8]

DOE lists the common types: tension seal, felt, reinforced foam, rubber tape, door sweeps, and bulb or fin seals. [S3]

Windows: sashes, frames and film

• Sashes. Window weatherstripping goes in the tracks and above, below and between the sashes. The Extension suggests metal or plastic V-channel in the tracks and between sashes, held with nails or staples even if it’s self-adhesive, and adhesive foam or vinyl between the sashes and frame. [S8]
• Frames. Caulk the fixed seam where the frame meets the wall. If the draft comes from behind the trim, DOE suggests backer rod plus caulk or low-expansion foam between the jamb and the framing, if the trim comes off without damage. ENERGY STAR rates that job moderate to difficult, about 1 to 2 days. [S1] [S5]
• Plastic film for winter. ENERGY STAR calls shrink-film kits an easy one-day job. Clean the frame, apply the tape, put the film on and tighten it with a hair dryer. Run it over the trim and it can stop leaks around the window too. In spring the tape pulls off without damaging the finish, ENERGY STAR says. [S6]
• Curtains. DOE says close curtains and shades at night and open them during the day to let in sun. If a window is still drafty after weatherizing, it suggests tight-fitting insulating shades. Low-e storm windows can save 10% to 30% on heating and cooling, depending on the windows you have. [S2]

Outlets, pipes and other holes

• Outlets and switches. DOE suggests foam gaskets behind outlet and switch plates on walls. [S2] [S8]
• Pipes and wires. Caulk and seal where plumbing, ducts or wiring come through walls, floors, ceilings and the soffits over cabinets. [S2]
• Chimneys, furnaces and water heater vents. Use fire-resistant materials only, such as sheet metal or drywall and furnace cement caulk, DOE says. For sealing around flues and vent pipes from chimneys, furnaces and water heaters, its air-sealing guide recommends a professional contractor. [S2] [S3]
• Fireplace. Check that the damper closes properly. [S2]
• Fire sprinklers. Don’t caulk around concealed sprinkler cover plates; DOE says to follow the sprinkler maker. [S1]

Combustion safety and fresh air

DOE compares insulation to a sweater and air sealing to a windbreaker. You want both, but a tighter house also traps more of what’s inside it. [S3]

ENERGY STAR says sealing a home or its ducts can, in some situations, make combustion appliances like water heaters backdraft, which is unsafe. A home energy professional can test for that, and ENERGY STAR says those problems should be fixed before sealing. A tight home can also trap radon, carbon monoxide and other pollutants and may need added mechanical ventilation. [S4]

DOE adds that stoves, fuel-burning furnaces and fireplaces need enough air, or they may release carbon monoxide. Our CO alarm placement guide covers where alarms go. [S3]

Once the drafts are sealed, the thermostat setback guide covers the other quick winter saving.

Older homes: lead paint first

Scraping old caulk, sanding or prying off trim makes dust. EPA says work in a pre-1978 home with lead-based paint can easily create dangerous lead dust, and if you can’t find out the home’s age, assume the paint has lead. [S9]

EPA recommends a lead-safe certified contractor. If you do the work yourself, it lays out lead-safe steps: contain the area, wear protection, keep dust down and clean up twice. ENERGY STAR points pre-1978 homes to the same EPA resources before trim work. [S5] [S9]

Your leak

Pick where you feel the draft to highlight what the sources say.

Before you seal

Quick answers