How to stop drafts from windows starts with finding where the air is actually moving, before buying anything. Most drafts come from one of three specific spots: worn weatherstripping at the sash meeting rail, cracked caulk where the frame meets the wall, or failed glazing putty around an old single pane. Each has a different fix, and using the wrong one wastes money without stopping the cold air.
Why a Window Drafts in the First Place
A window is not one sealed unit; it is a frame fixed to the wall and a sash that moves inside it, and each part fails differently.
The moving joint. On a double-hung window, the upper and lower sash slide past each other and meet at the middle, called the meeting rail. A thin strip of foam, felt, or spring metal, the weatherstripping, sits there and compresses when you lock the window, closing the gap. That strip ages. It flattens under years of compression, tears at the corners, or simply falls out, and once it stops compressing fully, the exact spot where two sashes meet becomes the exact spot where outside air gets in fastest.
The fixed joint. Where the frame meets the wall, and where a sash that never opens meets its own frame, the seal is caulk, not weatherstripping. Caulk shrinks and hardens with UV exposure and repeated hot-cold cycling, and after several years it cracks into hairline gaps you can miss just by looking.
The lock. Many double-hung windows use a cam lock at the meeting rail specifically to pull the two sashes together and compress the weatherstripping underneath them. If the lock isn't engaged, or a slightly warped sash keeps the cam from seating all the way, the seal never fully closes, even with brand-new weatherstripping installed. Check the lock before you touch anything else.
The glass itself is rarely the source, unless it's an older single-pane window with cracked or missing glazing putty, the compound that holds each pane into its wood frame. When that putty fails, air moves around the pane, not through it, and the fix is reglazing, not window film.
How to Stop Drafts From Windows: Find the Leak First
On a cold or windy day, run a bare hand slowly along the sash meeting rail, then the full perimeter where the frame meets the wall, then the corners. A moving air current feels distinct from ambient cold glass.
For a more precise read, hold a thin strip of tissue paper or a lit stick of incense a few inches from the same spots. If it flutters or bends where nothing should be moving air, that's your leak, and it tells you which fix applies: a draft at the meeting rail or sash channel is a weatherstripping problem, a draft along the frame-to-wall line is a caulk problem, and a draft that seems to come from the glass edge on an old window is a glazing putty problem.
Fix the Moving Parts With Weatherstripping, Not Caulk
Weatherstripping belongs on anything that opens: the sash channels and the meeting rail. The Department of Energy's Energy Saver program, read 2026-09-18, distinguishes the two jobs plainly: caulk is for stationary cracks and gaps generally under a quarter-inch wide, and weatherstripping is for the parts that actually move, like an operable window or a door. Its do-it-yourself weatherstripping guide for double-hung windows also gives a practical sizing tip: measure the total perimeter of everything you're weatherstripping and add about 10 percent for waste and mistakes before you buy the roll.
For a double-hung sash, a V-strip (also sold as a tension seal) fits into the channel the sash slides in and flexes as the window moves, which holds up longer than adhesive foam in a spot that gets used every season. Self-adhesive foam or felt strip works fine on the meeting rail itself and on stationary parts of the frame. A rolled fabric draft stopper along the bottom of the sash catches what the weatherstripping above it doesn't, and it's the cheapest thing on this list. None of this requires a ladder if you're working from inside the house, which is most of the job on most windows.
Seal the Fixed Frame With Caulk, Never the Moving Sash
Caulk goes where the window frame meets the siding or wall on the outside, and around any sash that's permanently fixed and never meant to open. It does not go on the track a sash slides in, on the meeting rail, or anywhere it could glue a working window shut. If a previous owner caulked an operable window closed, that's a repair job before it's a weatherization job.
Interior caulking, at the point where the window trim meets the wall inside the room, is a small, low-risk job you can usually finish with a caulk gun and a damp rag in under fifteen minutes per window.
When the Job Needs a Ladder, Stop and Check This First
Exterior caulking on a ground-floor window is a stable, step-stool job. Exterior caulking on a second story or higher is a different job entirely, because now the task is an extension ladder against the side of a house, and that is where the real risk in this whole project actually sits.
Falls from ladders are common enough that OSHA runs an ongoing fall-prevention campaign built around one rule, described on its ladder and fall-prevention training page (read 2026-09-18): maintain three points of contact at all times, meaning two hands and one foot, or two feet and one hand, in contact with the ladder, and always face the ladder while climbing. Never lean out to reach a spot instead of moving the ladder. Never set an extension ladder up near overhead power lines to reach a window; that turns a caulking job into an electrocution risk, and it's a stop condition, not a workaround. If the exterior gap you found is above what a stable step ladder reaches from solid ground, hire a window and door contractor or a painting contractor who carries the right ladder, harness practice, and insurance for height work, rather than improvising with a household extension ladder you don't use often.
Window Film and Interior Storm Panels, for the Glass Itself
If you've sealed the moving parts and the frame and a draft is still coming off the glass, the window is telling you something the weatherstripping can't fix: the glass or its seal is the weak point. Shrink film, a thin plastic sheet taped around the interior frame and tightened with a hair dryer, adds a still-air pocket between the film and the glass and is the cheapest option for a single season. It's cosmetic and temporary, and it comes off in spring.
A step up from film is a rigid interior storm panel or a magnetic acrylic insert, fitted to the inside of the existing window. These hold up for years, come off for cleaning, and don't require touching the original window or its exterior seals at all. If your front-line concern is nighttime heat loss rather than an active air leak, heavy, floor-length thermal curtains add a real layer of insulation and cost nothing to try before you buy anything else.
When Sealing Isn't Worth It Anymore
Weatherstripping and caulk fix a seal that's failed. They don't fix a sash that's warped enough that the lock can't pull it fully closed, a frame with rot at the sill, or a double-pane unit whose seal has failed between the panes, which shows up as fogging or a hazy ring you can't wipe away. Past that point you're pricing a repair against a replacement, and it's worth applying the same four-question framework this site uses for deciding whether an appliance repair still makes sense: what's the actual quoted cost, is a repair even possible on this unit, what's already failed, and what would a full replacement cost installed.
If a full window replacement is genuinely on the table, don't assume the label on a "high-efficiency" model tells you what you think it tells you. Read what an energy label actually tells you before you replace anything first, because the same caution about how an efficiency rating is measured and marketed applies to windows as much as it does to any other rated appliance.
FAQ
What's the single most common cause of a drafty window? Worn or missing weatherstripping at the point where the two sashes meet, called the meeting rail. It compresses less every year until air moves through the exact spot that's supposed to be sealed when the window locks.
Should I caulk or weatherstrip a window that won't fully close? Neither, until you check the lock. A cam lock that isn't fully engaged, or a slightly warped sash, can keep a window from closing tight regardless of how new the seal is. Fix the closure first.
Is window film actually worth doing? It's worth it as a cheap, temporary layer over glass that's still leaking air after the frame and sash are sealed, or on an old single-pane window you're not ready to replace. It's cosmetic, it's seasonal, and it won't fix a sealed-unit failure on a double-pane window.
Do I need a professional to fix drafty windows? Not for interior weatherstripping or interior caulking, which most homeowners can do with basic tools. Exterior caulking above the second story, or any point where a ladder would need to go near overhead power lines, is where this stops being a weekend job and becomes work for a licensed contractor with the right equipment.
How much does sealing a window actually reduce a draft? It depends on how much of the gap was the seal versus the glass itself, which is exactly why finding the draft's actual location with a hand test or tissue test comes before buying weatherstripping, caulk, or film. This page doesn't put a number on the saving because it varies by window, gap size, and climate, and a wrong number would be worse than none.
