How to seal a drafty window
Three solutions for three kinds of drafts, and when to skip DIY and replace the window instead.
Riley Brand
February 21, 2026
Diagnose the draft
Hold a lit candle near the window edges (carefully). Where the flame flickers, you have a leak.
Common spots: between sash and frame, where frame meets wall, around the latch on double-hungs.
The three fixes
Small gaps: foam weatherstripping tape. Peel-and-stick, ~$10 for a roll. Press onto the frame where the sash closes.
Medium gaps: V-strip (vinyl or metal). Slightly more work but lasts longer. ~$15.
Whole-window: shrink-film insulator kit. Tape clear film over the entire interior frame, blow with a hairdryer to shrink tight. ~$10/window. Removable in spring.
When to give up and replace
Visible water damage to the frame. The window won't close fully. Single-pane windows that fog between panes (failed seal).
At that point, even perfect weatherstripping wastes the next 10 years of heating bills.
People also ask
How much does this save?+
Drafty windows cost 10–25% of your heating bill. A few rolls of weatherstripping pays for itself in one winter.
Will weatherstripping prevent the window from opening?+
Properly applied, no — it compresses when the window closes, releases when it opens.
Caulking the outside — DIY?+
Yes. Buy paintable exterior caulk; remove old caulk first. The biggest mistake is caulking over the failed old caulk.