Weatherproofing Doors and Windows: Tools and Materials

Finding Air Leaks

Before you seal anything, find out where the leaks actually are. On a windy day, hold a lit incense stick near window and door frames, electrical outlets on exterior walls, and where pipes or wires penetrate the wall. The smoke stream will deflect visibly where air is leaking through. Work methodically around each room.

A thermal leak detector is a step up from the incense method. It reads surface temperature and indicates where cold spots exist on interior walls, which correlate with air infiltration. These cost about 30 dollars and give you a clear picture of which areas are losing the most energy. Focus your sealing efforts where the leaks are worst.

Door Weatherstripping

Exterior doors need weatherstripping on the top and both sides, plus a sweep or threshold seal at the bottom. For the top and sides, self-adhesive foam tape is the easiest to install but compresses and loses effectiveness within a year or two. V-strip (vinyl or metal tension strip) lasts much longer and provides a tighter seal because it springs back after each door closing.

A door sweep screws to the bottom edge of the door and seals the gap between the door and the threshold. Measure the door width, cut the sweep to length with a hacksaw, and attach it with the provided screws. Adjust it so it makes firm contact with the threshold without dragging hard enough to damage the floor. A correctly installed sweep should just brush the threshold when the door closes.

Window Weatherstripping

Double-hung windows leak at the sash channels (where the window slides up and down), the meeting rail (where upper and lower sashes overlap), and the gap between the sash and the frame. Spring bronze or V-strip installed in the sash channels provides a durable, nearly invisible seal. Self-adhesive foam tape works in the short term but compresses and peels over time.

For the meeting rail, a self-adhesive rubber or silicone strip compressed between the upper and lower sashes when closed seals the gap. For casement windows, replace the existing compression weatherstrip if it's flattened or torn. Most casement weatherstrip fits into a routed channel in the frame and can be pressed in by hand without adhesive.

Interior Sealing

Foam gaskets behind outlet and switch plates on exterior walls block a surprising amount of air. They cost about 25 cents each and install in seconds — remove the cover plate, place the gasket, reinstall the plate. While you're at it, install child safety plugs in unused outlets to further reduce airflow.

Attic access panels and whole-house fan covers are major air leak sources that people overlook. Attach adhesive-backed foam tape around the perimeter of the attic hatch where it rests on the frame. For pull-down attic stairs, a rigid foam board cover or an insulated tent that sits over the opening on the attic side blocks both air and heat transfer.

Window Film and Storm Windows

Plastic window film kits (heat-shrink film applied to the interior window frame with double-sided tape and a hair dryer) create a dead air space that reduces heat loss through single-pane windows by 40 to 50 percent. They're seasonal — install in fall, remove in spring. The film is nearly invisible once shrunk tight.

Interior storm windows are a more permanent solution. They mount inside the window frame with magnetic strips, clips, or compression gaskets. Acrylic or polycarbonate panels cost more than film but last for years and can be removed and reinstalled seasonally. For old single-pane windows where full replacement isn't in the budget, storm windows are the most effective intermediate step.

Frequently Asked Questions