Why are my windows so drafty?
Updated August 2026
Drafty windows are almost always caused by worn or missing weatherstripping and cracked, gapping caulk around the frame, not by the glass itself. Fresh weatherstripping and a bead of exterior caulk cost $10 to $40 in materials and stop most drafts in an afternoon. The U.S. Department of Energy estimates that air leaks account for roughly 25% to 30% of a home's heating and cooling energy use, so sealing these gaps pays back quickly in both comfort and lower bills.
Causes, most likely first
| Cause | How likely | The fix | Typical cost |
|---|---|---|---|
| Worn or missing weatherstripping | Most common | Replace the compressed or torn weatherstripping in the sash and jamb with new foam, V-seal, or bulb stripping. | $10–30 |
| Cracked or gapping exterior caulk | Common | Rake out the old, split caulk around the frame and re-caulk the exterior perimeter with a quality sealant. | $8–20 |
| Failed or misaligned sash locks | Common | Locks that do not pull the sash tight leave a gap; adjust or replace the lock so the window closes snug. | $10–40 |
| Aging single-pane glass | Occasional | Single-pane windows radiate cold and leak; add interior storm panels or a shrink-film kit, or budget replacement. | $15–40 kit |
| Gaps under the interior trim | Occasional | Air leaks through the unsealed cavity behind the casing; pull the trim and fill it with foam backer rod and low-expansion foam. | $10–25 |
| Rotted or warped frame | Rare | A wood frame that has rotted or racked will not seal; repair the wood or replace the unit. | $200–1,000+ |
Check these first
- On a windy or cold day, run a damp hand or a lit incense stick around the window edges; the smoke or the chill reveals exactly where air is leaking.
- Inspect the weatherstripping for gaps, tears, or flattened sections that no longer seal.
- Check the exterior caulk for cracks, shrinkage, and spots where it has pulled away from the frame or siding.
- Confirm the sash locks pull the window tight; an unlocked or misaligned sash often leaves a visible gap.
- Look for daylight around the closed sash and feel for drafts at the corners, the usual weak points.
Prevent it next time
Weatherstripping and caulk are consumables, not one-time fixes: they harden, crack, and lose their seal over a few years. Re-seal the exterior frames on a regular schedule so gaps never open up, following how often to reseal window frames, and fold a draft check into your windows maintenance checklist each fall. When the frames themselves wear out, how often to replace windows helps you plan the bigger investment.
When to call a pro
Handle weatherstripping, caulk, and film kits yourself; they are cheap and easy. Call a pro when the frame is rotted or racked, when a sash will not close square, or when you are weighing replacement. New weatherstripping runs $10 to $40 per window in materials, frame repair $200 to $600, and full window replacement $450 to $1,500 per window installed. Our guide on how long windows last helps you decide when sealing has run its course.
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Stop chasing symptoms, free for 30 daysFrequently asked questions
Is it cheaper to seal drafty windows or replace them?
Sealing wins by a wide margin for the drafts themselves. Weatherstripping and exterior caulk cost $10 to $40 per window in materials and stop most air leaks in an afternoon, while full replacement runs $450 to $1,500 per window and takes years of energy savings to pay back on drafts alone. Replace when the frames are rotted, the sashes will not close, or single panes are failing, but if the glass and frame are sound, sealing is the far smarter first spend.
How do I find exactly where a window is leaking air?
On a cold or windy day, slowly move a lit incense stick or a damp hand around the entire window perimeter. Where the smoke bends sharply or your skin feels a chill, air is moving through a gap. Common leak points are the weatherstripping between the sashes, the joint where the frame meets the wall, and the corners of the sash. A cheap confirmation is to look for daylight around a closed sash. Mark each leak with tape, then seal them one by one.
Will new weatherstripping really make a difference on my heating bill?
It can. Air leaks around windows and doors are a meaningful chunk of a home's heat loss, and the Department of Energy estimates air leakage accounts for roughly 25% to 30% of heating and cooling energy use. Sealing the gaps around several drafty windows for a few dollars each reduces that loss and makes the rooms noticeably more comfortable, with fewer cold spots near the glass. It is one of the highest-return, lowest-cost improvements you can make in a weekend.
Should I use plastic film over windows in winter?
Interior shrink-film kits are a cheap, effective stopgap, especially on old single-pane windows. A $15 to $40 kit covers several windows, and the trapped air layer cuts drafts and adds a bit of insulation, often reducing the chill you feel near the glass. The downsides are that you cannot open the window while it is on and it comes off in spring. Use film as seasonal help on your worst windows while you plan permanent fixes like weatherstripping, caulk, or eventual replacement.