Weatherproofing Doors and Windows: Tools and Materials

Air leaks around doors and windows account for 25 to 30 percent of heating and cooling energy loss in a typical home, according to the U.S. Department of Energy. Sealing them is one of the best returns on investment in home improvement. Most weatherproofing projects cost under $50 in materials and pay for themselves within a single heating season through lower energy bills.

Finding Air Leaks

Before you seal anything, find out where the leaks actually are. On a windy day, hold a lit incense stick or a thin strip of tissue paper near window and door frames, electrical outlets on exterior walls, and where pipes or wires penetrate the wall. The smoke stream or tissue will deflect visibly where air is leaking through. Work methodically around each room, starting with the north-facing walls where wind-driven infiltration is typically worst.

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. The Black & Decker TLD100 and similar models cost about $25 to $35 and give you a clear picture of which areas are losing the most energy. Point the detector at the wall from about 12 inches away and watch for temperature drops of 5 degrees or more compared to the surrounding surface. Focus your sealing efforts where the leaks are worst rather than weatherstripping every window equally.

For a more thorough assessment, a professional energy audit uses a blower door test to pressurize the house and measure total air infiltration in cubic feet per minute. These audits run $200 to $400 but many utility companies offer them at a discount or free as part of efficiency programs. The audit identifies not just doors and windows but also hidden leaks in the attic floor, basement rim joist, and HVAC ductwork that you might not find with the incense method.

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. It works as a temporary fix or for interior doors but is not the best long-term solution for exterior doors that open and close daily. Frost King and M-D Building Products both sell foam tape kits sized for standard doors for about $5 to $8.

V-strip (vinyl or metal tension strip) lasts much longer and provides a tighter seal because it springs back after each door closing. Bronze V-strip can last 20 years or more. Cut it to length with tin snips, peel the adhesive backing (or nail it in place for metal versions), and press it into the door stop where the door contacts the frame. The V opens slightly as the door closes against it, creating a compression seal that stays effective through thousands of cycles.

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. The Frost King A79 and M-D Building Products 05587 are two common aluminum-and-vinyl sweeps available at most hardware stores for $8 to $15. For more on exterior sealing, see our Exterior Caulking Guide.

Window Weatherstripping

Double-hung windows leak at three main points: 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. The metal strip sits in the channel and presses against the sash as it slides, blocking air without adding significant friction to window operation. This is the preferred method for older wood windows where appearance matters.

Self-adhesive foam tape works in the short term but compresses and peels over time, especially on windows that are opened and closed frequently. For windows that stay closed most of the year (like a bedroom window that only opens in summer), foam tape is adequate and much faster to install. For windows that get regular use, spring bronze or tubular silicone weatherstrip is the better investment.

For the meeting rail on double-hung windows, a self-adhesive rubber or silicone strip compressed between the upper and lower sashes when closed seals the gap. For casement windows (the crank-out type), replace the existing compression weatherstrip if it is flattened or torn. Most casement weatherstrip fits into a routed channel in the frame and can be pressed in by hand without adhesive. Marvin, Pella, and Andersen sell replacement weatherstrip kits specific to their window models, typically for $10 to $20 per window.

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 pre-cut foam gasket over the outlet or switch, and reinstall the plate. While you are at it, install child safety plugs in unused outlets to further reduce airflow through the outlet openings. A pack of 24 gaskets costs about $5 and covers every outlet on an exterior wall in most homes.

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. Use the thickest foam that still allows the hatch to seat properly, typically 3/8-inch or 1/2-inch closed-cell foam. For pull-down attic stairs, a rigid foam board cover or an insulated tent (like the Attic Tent AT-5) that sits over the opening on the attic side blocks both air and heat transfer. The gap around pull-down stairs can leak as much air as leaving a window open year-round.

Basement rim joists (where the floor framing sits on the foundation wall) are another overlooked source of air infiltration. Seal them with canned spray foam insulation applied between each floor joist where it meets the rim board. A can of Great Stuff or DAP Touch 'n Foam costs about $5 to $8 and covers 50 to 100 linear feet depending on gap size. This is one of the highest-impact air sealing tasks in a home with an unfinished basement. For a deeper look at insulation options, see our Insulation Tools Guide.

Window Film and Storm Windows

Plastic window film kits create a dead air space that reduces heat loss through single-pane windows by 40 to 50 percent. The film attaches to the interior window frame with double-sided tape and then shrinks tight with a hair dryer, creating a transparent, taut layer. The 3M Indoor Window Insulator Kit and Frost King V73 are two widely available options, running $5 to $8 per standard window. Install in fall, remove in spring. The film is nearly invisible once shrunk tight and does not block light.

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 ($30 to $100 per window depending on size) but last for years and can be removed and reinstalled seasonally. Indow Windows and WindowSeal are two companies that make custom-fit interior storm panels with magnetic seals. For old single-pane windows where full replacement is not in the budget, storm windows are the most effective intermediate step.

Exterior storm windows are another option, particularly for older homes with wood-frame single-pane windows. Aluminum-frame exterior storms cost $50 to $150 per window installed and provide both air sealing and an additional insulating air gap. They also protect the primary window from weather exposure, extending its lifespan. The combination of interior weatherstripping plus an exterior storm window brings single-pane performance close to that of a basic double-pane replacement window at a fraction of the cost.

Frequently Asked Questions

What Is the Best Weatherstripping for an Exterior Door?

For the sides and top, spring bronze or stainless steel V-strip provides the longest-lasting seal, with manufacturer specs indicating 20 or more years of reliable performance. For a quicker but shorter-lived option, tubular silicone or EPDM rubber weatherstrip nailed to the door stop compresses when the door closes and provides a good seal for 5 to 10 years. Avoid self-adhesive foam tape for exterior doors. It compresses permanently within a season or two and stops sealing effectively, especially on doors that see heavy daily use.

How Much Money Can Weatherproofing Actually Save?

The Department of Energy estimates that sealing air leaks can reduce heating and cooling costs by 10 to 20 percent. For a household spending $2,000 a year on energy, that is $200 to $400 in savings. Weatherstripping and caulking materials for an entire house typically cost $50 to $150 total, so the payback period is a few months to one heating season. The savings are higher in older, leakier homes and in climates with extreme winter or summer temperatures where the conditioned-to-outdoor temperature difference is large.

Should I Weatherstrip Interior Doors?

Only if the interior door separates conditioned from unconditioned space. Doors to attached garages, unheated basements, and unfinished attic stairways benefit from weatherstripping because they act as boundaries between heated and unheated zones. Doors between rooms that are all heated and cooled do not need it. The exception is if you are isolating rooms for zone heating or cooling. Weatherstripping the doors to rooms you do not use reduces the volume you need to condition and can lower energy costs further.

Related Reading

• Exterior Caulking Guide
• Window Replacement Tools