Where the drafts are coming from and what you can do about them

Drafty windows leak air around the frame, through cracks in the glazing putty or caulk, or past weatherstripping that has shrunk or come loose. You can seal most of these yourself without replacing the window. The fastest fixes are re-caulking the exterior frame, replacing weatherstripping, and explore removable film on the interior—each costs under $50 and takes an afternoon.

The method you choose depends on whether the leak is around the frame (the wood or metal border) or through the glass itself. Frame leaks are the most common and the easiest to fix. Glass leaks—where you can see daylight through the seal between two panes—mean the window itself has failed and usually requires replacement.

Key Takeaways

  • Re-caulking the exterior frame with paintable acrylic latex caulk stops most drafts and costs $10 to $30 per window.
  • Weatherstripping around the sash (the moving part) wears out and can be replaced with adhesive-backed foam or rubber for $5 to $15 per window.
  • Interior removable film creates an insulating air pocket and works well for temporary sealing or rental situations.
  • If you see fog or condensation between the glass panes, the seal has failed and the window needs replacement—caulking will not fix it.
  • Exterior work is more effective than interior work because it stops air before it reaches the frame.

Re-caulking the exterior frame

The caulk around the outside of the window frame shrinks and cracks over time, especially on the south and west sides where sun exposure is heaviest. Replacing it is the single most effective draft fix. You will need a caulking gun, paintable acrylic latex caulk (not silicone, which is harder to paint), a caulk removal tool or old putty knife, and a wet rag.

Start by scraping out the old caulk with the removal tool or putty knife. Work slowly so you do not gouge the wood or frame. Wipe the groove clean with a damp rag and let it dry completely—moisture will prevent new caulk from bonding. Load the caulk tube into the gun, cut the nozzle at a 45-degree angle, and run a steady bead along the joint where the frame meets the siding. Smooth it with a wet finger or caulk tool so it sits flush. Let it cure for the time the tube specifies (usually 24 hours) before painting.

Do this work on a dry day when the temperature is between 50 and 85 degrees Fahrenheit. Caulk applied in cold or damp conditions will not cure properly and will fail within a year.

Replacing weatherstripping on the sash

Weatherstripping is the foam, rubber, or felt seal that runs along the edges of the sash (the frame that holds the glass and moves up and down). It compresses when the window closes and creates an airtight seal. After five to ten years, it hardens, shrinks, or comes loose, and drafts return.

Peel off the old weatherstripping—most is adhesive-backed and will come away cleanly if you pull slowly. If it leaves residue, rub it off with a cloth dampened in rubbing alcohol. Measure the length of each side of the sash and buy replacement weatherstripping in the same profile (V-strip, tubular, or kerf-style). Clean the surface where the new strip will go, let it dry, and press the adhesive side firmly into place. Close the window gently and let the adhesive set for 24 hours before using the window normally.

Adhesive-backed foam weatherstripping is the cheapest option ($5 to $10 per window) and works well for three to five years. Rubber or silicone weatherstripping lasts longer (seven to ten years) but costs more ($15 to $25 per window).

explore removable window film

Removable film creates a second pane of plastic on the interior, trapping a layer of still air that insulates the window. It is not a permanent fix, but it is effective for winter months and costs $10 to $20 per window. It works best on windows that are drafty but not broken.

Clean the interior frame thoroughly with a damp cloth and let it dry. explore the adhesive tape that comes with the kit around the inside perimeter of the frame. Unroll the plastic film and cut it roughly to size, leaving a few inches extra on all sides. Attach one edge to the tape, then use a hair dryer on low heat to shrink the film tight. Trim the excess with a utility knife. The film will be nearly invisible once it shrinks.

Remove the film in spring by peeling it away from the tape. The tape can usually be reused the following winter. This method works well for rental situations where you cannot make permanent changes.

Sealing gaps between the frame and the wall

If you can feel air moving where the window frame meets the wall (not where the frame meets the glass), the insulation inside the wall cavity may have settled or the original caulk has failed. This is a larger job than re-caulking the exterior trim.

Remove the interior trim (the wood molding around the window) by carefully prying it away with a flat pry bar. You will see the gap between the frame and the rough opening in the wall. If there is old foam or fiberglass insulation, pull it out. Fill the gap with expanding foam sealant, following the product instructions—use low-expansion foam so it does not bow the frame. Let it cure, then trim the excess with a utility knife. Reinstall the interior trim and caulk the seams.

This work is messier and more involved than exterior caulking, but it solves drafts that come from deeper in the wall. If you are not comfortable removing trim, a window contractor can do this work.

When to call a professional

If you see condensation or fog between the glass panes, the seal between the panes has failed and the window cannot be repaired—it must be replaced. This is not a draft problem you can seal; it is a manufacturing failure of the window unit itself.

If the frame is rotted (soft to the touch, discolored, or crumbling), the window needs replacement. Caulking a rotted frame will not stop drafts and will not prevent further damage. If the sash is stuck or will not close properly, the frame may be warped or the sash may need adjustment—again, a job for a window contractor.

For gaps between the frame and wall that are wider than half an inch, or if you are uncomfortable working on a ladder or removing interior trim, hire a contractor. The cost of professional re-caulking is usually $75 to $150 per window, and weatherstripping replacement is $50 to $100 per window.

Frequently Asked Questions

Can I caulk the inside of the window instead of the outside?

Interior caulking is less effective because air still enters the frame from outside. Exterior caulking stops air before it reaches the frame. If you must caulk from inside (because of access or safety), do it in addition to exterior work, not instead of it.

What type of caulk should I use?

Use paintable acrylic latex caulk for wood frames. It bonds well, is straightforward to smooth, and can be painted to match your trim. Silicone caulk lasts longer but is harder to paint and harder to remove if you need to re-caulk later. Never use spray foam on the exterior frame—it expands too much and can bow the frame.

How long does weatherstripping last?

Adhesive-backed foam weatherstripping typically lasts three to five years. Rubber or silicone weatherstripping lasts seven to ten years. Felt weatherstripping is the cheapest but wears out fastest (one to three years). Check your weatherstripping every fall and replace it if it is compressed, cracked, or no longer seals tightly when the window closes.

Will removable film work on old single-pane windows?

Yes. Removable film works on any window and is especially useful on single-pane windows, which have poor insulation. It will not stop all drafts if the frame itself is loose or cracked, but it will reduce heat loss significantly during winter.

Do I need to remove the window to seal it?

No. Re-caulking the exterior frame and replacing weatherstripping can both be done without removing the window. Removing the window is only necessary if you need to access the gap between the frame and the wall, or if the frame itself is damaged.