Guide
How to stop window drafts
Moving air and a cold surface feel identical and need completely different fixes. Five minutes with a candle settles it.
By Janet H. · Last updated September 23, 2026 · How we choose
Test first: hold a lit candle or a smoking incense stick along the frame on a windy day. If the flame or smoke pulls sideways, you have an air leak and you need to seal it. If it stays steady but the area still feels cold, you have a cold surface and you need to cover it. These feel identical standing in the room and need completely different fixes, which is why so many people buy thermal curtains for a problem curtains cannot touch.
Sealing is also far cheaper than covering. Do the test, do the sealing, and only then decide whether you still need a curtain.
Drape & Dawn earns a commission from qualifying purchases made through links on this page, at no extra cost to you. It does not change what we recommend. Full disclosure.
Testing
Step 1 — find the leaks
Pick a windy day; a still day will hide small leaks. Work slowly around each window with the flame a couple of inches from the surface, and check all of these:
- Where the sash meets the frame — the commonest leak on any opening window, and the one worn weatherstripping causes.
- Where the frame meets the wall — a gap here often means failed caulk, sometimes hidden behind the trim.
- The sash lock — a loose or misaligned lock leaves the two sashes apart. Often fixed by adjusting the keeper, at no cost.
- Weep holes and trickle vents — these are meant to be open. Do not seal them; they prevent condensation problems.
- Around the glass itself — failed glazing putty or a perished seal on an older window.
Fixes
Step 2 — seal what you found
- 1
Adhesive foam or V-strip on the sash
Self-adhesive foam tape is the quick fix for a gap between sash and frame. V-strip (tension seal) lasts longer and works better on a sliding sash because it springs against the moving part instead of being compressed by it.
- 2
Caulk where the frame meets the wall
A gap between frame and wall is a straight path to outside. Clean it out, then run a bead of exterior-grade caulk. This is the highest-return ten minutes in the whole exercise.
- 3
Adjust the lock before you buy anything
On a double-hung or casement window, tightening or repositioning the lock often pulls the sashes together enough to close the leak entirely. Free, and frequently sufficient.
- 4
Rope caulk for a window you won't open
For a sash you will not open until spring, rope caulk pressed into the gap seals it completely and peels out cleanly later. Ugly at close range, effective, and cheap.
- 5
Shrink film for the whole opening
If the window is single glazed or leaking in several places at once, a shrink-film kit seals the entire opening and adds an air gap. It seals the window shut for the season, so not on anything you need to open.
After sealing
Step 3 — then cover the cold glass
Once the air leaks are sealed, what remains is a cold surface and the convection current it generates. That is what a covering addresses, and now it can do its job: a cellular shade fitted tightly in the recess, or thermal curtains sealed at the top and reaching the floor.
Doing it in this order matters. A curtain over an unsealed leak just billows gently while cold air continues to enter the room, and you end up concluding that thermal curtains do not work — when in fact they were never the right tool for that problem.
Next step
What to buy
Weatherstripping and caulk come first and cost very little. If the glazing is single, a film kit is the next best value. Coverings come last and are in best thermal curtains and best insulated cellular shades.
What we’d buy
The products behind this advice
Picked against the criteria above, not the other way round. We don’t show prices because we don’t have a live price feed — each link goes to the current listing.
| # | Best for | Product | Type | Stage | Price |
|---|---|---|---|---|---|
| 1 | After sealing — the glass | Indoor Window Insulator Kit Single glazing and windows leaking in several places at once. | Insulation film | — | Check price on Amazon #ad We don’t show prices — check the current one on Amazon. How we’re funded |
| 2 | After sealing — the covering | Cordless Cellular Shades, light filtering The cold-surface convection that remains once the leaks are closed. | Cellular shade | — | Check price on Amazon #ad We don’t show prices — check the current one on Amazon. How we’re funded |
| 3 | If the opening is awkward | Thermal Insulated Blackout Curtains, silver backed Bays, doors and shallow recesses where a fitted shade will not go. | Thermal curtain | — | Check price on Amazon #ad We don’t show prices — check the current one on Amazon. How we’re funded |
01 — After sealing — the glass
Indoor Window Insulator Kit
3M
Shrink film taped across the whole window opening and heat-shrunk tight, creating a genuine second sealed air gap. On single glazing it is the highest thermal return per dollar of anything in this category.
Who it’s for: Single glazing and windows leaking in several places at once.
The catch: It seals the window shut for the season, so it is out on anything you need to open or that is an escape route. And it is visible for what it is.
At a glance
- Type
- Insulation film
- Fitting
- Tape and heat shrink
- Season
- Autumn to spring
- Best on
- Single glazing
#ad We don’t show prices — check the current one on Amazon. How we’re funded
02 — After sealing — the covering
Cordless Cellular Shades, light filtering
CHICOLOGY
Made-to-size honeycomb that seals against the recess, diffusing daylight into an even glow with no hotspot while insulating the glass behind it.
Who it’s for: The cold-surface convection that remains once the leaks are closed.
The catch: Opaque, including the light-filtering fabric — lowering it means losing the view entirely. There is no partial-view position.
At a glance
- Type
- Cellular shade
- Fabric
- Light filtering
- Operation
- Cordless
- Fit
- Made to size
#ad We don’t show prices — check the current one on Amazon. How we’re funded
03 — If the opening is awkward
Thermal Insulated Blackout Curtains, silver backed
Deconovo
A silver-tone thermal coating facing the glass reflects solar radiation back out before the fabric can absorb it — the mechanism that separates a genuinely heat-rejecting panel from a merely heavy one.
Who it’s for: Bays, doors and shallow recesses where a fitted shade will not go.
The catch: The coating is the failure point: it stiffens along fold lines and does not tolerate a hot wash or a tumble dryer. Expect a shorter life than an uncoated weave.
At a glance
- Type
- Thermal curtain
- Construction
- Woven, silver coated
- Care
- Gentle cold, no heat
- Drops
- 63 / 84 / 96 in
#ad We don’t show prices — check the current one on Amazon. How we’re funded
FAQ
Questions people actually ask
How do I know if my window has a draft or is just cold?
Hold a lit candle or a smoking incense stick along the frame on a windy day. Sideways movement means moving air and a leak to seal. A steady flame beside a cold area means a cold surface, which needs covering rather than sealing.
What's the cheapest way to stop a window draft?
Adjust the sash lock — often free and often sufficient. After that, self-adhesive foam weatherstripping on the sash and a bead of caulk where the frame meets the wall. Both cost very little and outperform any curtain.
Will thermal curtains stop a draft?
No, not a real air leak. A curtain over an unsealed gap billows gently while cold air keeps entering the room. Curtains address the cold-surface convection problem, which is a different thing that feels similar.
Should I seal the little holes at the bottom of my window frame?
No. Those are weep holes and they let water drain out of the frame. Sealing them causes water to pool inside the frame, which is a much more expensive problem than a draft.
Is it worth using shrink film?
On single glazing, very much so — it seals the whole opening and adds an air gap for very little money. On modern double glazing the gain is small. Either way, the window is sealed shut for the season.
Keep going
Read next
Drafts
Insulated curtains vs window film
Film performs better and looks worse. Curtains, the reverse. Here's how to choose.
Drafts
Best thermal curtains
Panels worth buying — and the sealing that doubles what any of them achieve.
Drafts
Best insulated cellular shades
The strongest thermal performer in window coverings — if you measure the fit properly.
Drafts
Do thermal curtains save energy?
Real effect, unquantifiable savings — and the four things that decide how much you get.
Drafts
Summer vs winter curtain setup
Same curtains, opposite routine — the free change most people never make.
About the author
Janet H.
Janet H. is the owner of Janet Media Group and the person behind Drape & Dawn. She researches every pick against the site's published methodology.
Published by Janet Media Group · Last updated September 23, 2026