Here's the good news about a drafty window: the glass is rarely the problem. Air sneaks in around the parts that move — the sash edges, the meeting rail where the two sashes overlap, the trim. And moving parts are cheap to seal. Work this list in order and stop when the draft stops. Most windows quit somewhere around fix two or three.
On a windy day, light an incense stick and move it slowly around the frame, the sash edges, and the lock. Where the smoke wavers or streams sideways, air is moving. No incense handy? The back of your hand works — skin is surprisingly good at feeling a thin leak — or hold a tissue against the edges and watch it flutter. Mark each leak with painter's tape so you fix causes instead of guesses. It's the same trick used house-wide in our guide to finding and sealing air leaks in your home.
Lock the window — really. Sounds insulting; works constantly. A sash lock doesn't just secure the window, it pulls the two sashes together at the meeting rail and compresses the seal between them. A window that's closed but unlatched leaks far more than you'd expect. If the lock is broken or the sashes no longer meet, a replacement latch costs a few dollars and ten minutes.
Press in rope caulk. A soft, putty-like cord you push into the joints between sash and frame with your fingers. A box costs a few dollars, goes on in minutes, and peels off clean in spring, which makes it completely renter-safe. It's for windows you don't need to open until the weather turns.
Replace the weatherstripping. Old foam tape compresses flat and stops sealing within a few seasons. V-strip (tension seal) pressed into the sash channels of a double-hung window lasts for years and still lets the window slide. Adhesive foam tape is cheaper and easier, and shorter-lived. Budget roughly $5–$15 of material per window either way. Doors take the same materials in a different groove — our step-by-step on how to replace weatherstripping on a door covers the kerf, adhesive, and V-strip versions for that job, corners included.
Renew the exterior caulk. Step outside and look at the joint between the window frame and the siding. Cracked, shrunken caulk there lets wind drive into the wall cavity and out through your interior trim. Cut away the failed bead and run new exterior-grade caulk. Leave the small weep holes at the bottom of the frame open while you work — they drain water, and sealing them traps moisture inside the frame.
Put up a shrink-film kit. Clear film taped over the whole interior frame and shrunk drum-tight with a hair dryer. It sounds like a hack and genuinely works, because it traps a still layer of air over the entire window — roughly the same trick a storm window plays, for a few dollars. Our look at whether window insulation film works covers the results and the downsides. The main one: that window doesn't open again until you peel the film off in spring.
Add storm windows. A second layer over the whole opening. Exterior storms often run $100–$300 per window installed; interior inserts cost more but go in without ladders or screws, which suits historic windows and rentals. Either way you get a dead-air gap, less condensation on the main window, and noticeably less street noise as a side benefit.
Replace the sash or the whole window. The permanent fix, and the only one on this list that addresses rotted wood, a sash warped so badly it won't meet the frame, or a failed double-pane seal — that's the window fogging between the panes, and no amount of caulk helps it. If that's your symptom, read why windows fog up before pricing replacements. Replacement commonly runs several hundred dollars per window and up, installed, so it should be the last stop on the ladder, not the first.
| Fix | Rough cost per window | How long it lasts | Window still opens? |
|---|---|---|---|
| Latch repair or adjustment | $0–$10 | Years | Yes |
| Rope caulk | A few dollars | One season | Not until removed |
| New weatherstripping | $5–$15 in materials | About 3–10 years, by type | Yes |
| Exterior caulk | Under $10 | About 5–10 years | Yes |
| Shrink-film kit | A few dollars | One season | No |
| Storm window | Often $100–$300 installed | Decades | Yes |
| Full replacement | Several hundred and up | Decades | Yes |
Caulking the sash to the frame as a "repair." You've sealed it, all right — including next June, when you want it open. Rope caulk exists precisely so you don't have to do this.
Sealing the inside while the leak is outside. Interior trim caulk hides the symptom and leaves the wind path into the wall wide open. Fix the exterior joint first; the inside bead is the finishing layer.
Jumping straight to replacement. Ten dollars of V-strip has quietly killed a lot of four-figure window quotes. Climb the ladder first and replace only the windows that are rotted, warped, or fogged.
Filming over a fogged window. Film stops moving air. Fog between the panes is a dead seal, a different failure entirely, and it will still be there — now behind plastic.
Drafts are a ladder, not a leap. Find the leak, lock the sash, spend the ten-dollar fixes first, and climb only as high as you need to. In most houses the draft dies at fix two or three. Save replacement money for the windows that are actually dying — the rotting and the fogged — not for windows that merely leak a little air.
Rope caulk or a shrink-film kit, both a few dollars per window. But check the latch and weatherstripping first — they cost about the same, keep the window usable, and last for years instead of one season.
Yes. The film traps a layer of still air across the whole window, which is the same principle as a storm window, and the difference in comfort next to the glass is easy to feel. The costs are one season per application and a window that stays shut until spring.
Outside first. The joint between the frame and the siding is the weather barrier, and that's where failed caulk lets wind and water in. Interior caulk around the trim is worth doing too, but it's the second layer, not the fix.
When the frame is rotted, the sash is warped and won't meet or lock, or the insulated glass seal has failed and the window fogs between the panes. If the wood is sound and the sash still moves, the cheap fixes on this list will handle the draft.
Yes. Rope caulk, film kits, and adhesive foam tape all come off cleanly at move-out and need no landlord-level changes. Skip anything that involves cutting, screws into the frame, or exterior caulk on a building you don't own.