How to Stop Drafts Around Windows and Doors

One room stays cold, the couch by the window is unusable, and the heat runs constantly. The instinct is to buy window film and cover everything, but the draft felt near a window is often cold glass chilling the air beside it rather than air coming in, and the actual leaks are usually somewhere else on the frame. Find them before buying anything.

Find the leaks with smoke or a damp hand

Pick a windy day, close the house up, and run the kitchen and bathroom exhaust fans to pull the interior slightly negative. Move a lit incense stick slowly along the edges of each window and door. Where the smoke pulls sideways, there is a leak. A damp hand works nearly as well.

Lock every double hung window

A double hung sash lock does not only lock, it pulls the upper and lower sashes tight against each other and closes the gap where they meet. Going through the house and locking every window costs nothing and closes a real leak.

Fit a sweep under exterior doors

The gap under an exterior door is usually the single biggest leak in the house at eye level. Measure the door width, cut a sweep to length, and screw or stick it so the blade or brush just touches the threshold without dragging hard enough to make the door stick.

Weatherstrip the door frame and window channels

Clean the stops with rubbing alcohol and let them dry, then run adhesive backed V strip or closed cell foam along the surfaces the door closes against, including the latch side and the top. For a sash that rattles in its channel, V strip in the channel takes up the play.

Caulk the trim and the frame gap

Weatherstripping seals moving parts, caulk seals fixed ones. Run a bead where the trim meets the wall and where it meets the frame, and use exterior grade caulk on the outside casing. If trim is already off for other work, low expansion foam in the gap between frame and rough framing seals the biggest hidden leak of the group.

Add film or a storm window for the season

Interior shrink film is inexpensive, takes an afternoon, and cuts both the draft and the cold radiating off single pane glass for one winter. An interior or exterior storm window does the same permanently.

Windows are rarely the biggest leak in a house. Most of the air loss is in the attic hatch, recessed light cans, the rim joist above the foundation, and pipe and wire penetrations. Window work is the place to start only when the smoke test says the windows are the problem.

If the house has an atmospheric gas or oil appliance. Sealing a house tighter can starve a naturally vented water heater or furnace of combustion air. Soot around the draft hood or a persistent fuel odor means a licensed technician needs to check the venting.