In an older home, winter often announces itself at the windows first. A cold draught across the floor, a curtain that moves when the window is shut, a room that never quite warms up no matter how high the heating is set — these are classic signs that air is leaking around old frames, sashes and seals. Replacing every window is expensive and disruptive, but most draughts can be reduced a great deal with simple DIY work, and the comfort difference is usually felt the same evening.
The short answer is to find the leaks first, then seal them in order of impact: lock the windows properly, replace worn weatherstripping, reseal the frame-to-wall joint outside where needed, and add window film or thermal curtains for single-glazed windows. Start with the rooms you use most and the windows that face the prevailing wind. If a window is rotten, painted shut, or fogged between the panes, DIY sealing will help comfort but will not restore the window — that needs repair or replacement.
Why Older Windows Leak Air in Winter
Older windows were not built to modern airtightness standards, and decades of use make the gaps worse. Timber sashes shrink and swell with moisture, paint builds up in the channels, weatherstripping compresses and hardens, and putty and caulk crack as frames move with temperature changes. Single glazing also loses heat through the glass itself, which is different from a draught but feels similar: cold glass chills the air next to it, and that cold air then sinks across the floor.
It is useful to separate draughts from cold glass, because the fixes differ. A draught is moving air coming through a gap, and it can usually be felt with a hand or seen with a smoke test. Cold glass, by contrast, is conduction and radiation through the pane, and it is best addressed with window film, secondary glazing, or thermal curtains. Many older homes have both problems at once, which is why a combination of sealing and insulation usually works better than any single product.
Finding Every Winter Window Leak Before You Seal Anything
On a windy, cold day, walk slowly around each window with the back of your hand near the frame, the sash meeting rail, and the sill. A draught will feel like a distinct cool stream, not just general cold. For a more precise test, hold a lit incense stick near the edges — never near curtains — and watch the smoke: a steady vertical rise means no leak, while smoke blowing sideways marks one. Do this room by room and note which windows leak most, because sealing the worst offenders first gives the fastest comfort gain.
Also check the outside of the frame where it meets the wall. Cracked, missing or pulling-away exterior caulk is a direct path for cold air and water, and it is often missed because people only seal the inside. Look for daylight around a closed sash, for paint that has cracked along the sash channel, and for locks that do not pull the sashes tightly together. A window that will not lock properly will almost always draught, however much tape you add around it.
Locking and Weatherstripping: The Fastest Old-Window Draft Fix
Locking a window is not just about security. On a double-hung window, the lock pulls the two sashes together and closes the gap at the meeting rail, which is one of the most common leak points. Before you add any product, clean the sash channels, remove loose paint flakes, and make sure both sashes move and lock fully. For large windows, two locks placed a few inches from the outside edges close the gap more evenly than a single central lock.
Weatherstripping is the next step, and matching it to the gap is essential. Foam tape is cheap and easy, but it compresses over time and suits small, even gaps. V-strip, also called tension seal, springs back and suits the sides of sliding sashes. Rubber or silicone bulb seals suit larger, uneven gaps around casements. Clean the surface, measure the gap, cut the strip to length, and press it firmly into place. If the strip is too thick, the window will not close; if it is too thin, it will not seal. Replace weatherstripping when it is flattened, torn, or no longer springs back.
Sealing the Frame, Sill and Wall Joint Around Old Windows
The joint between the window frame and the wall is a frequent leak that weatherstripping cannot fix, because it is outside the sash. Inside, a thin bead of paintable caulk along a cracked frame-to-wall joint can help, but the more important seal is outside, where wind and rain first meet the house. Scrape out failed exterior caulk, clean the joint, and apply exterior-grade sealant on a dry day when the temperature is above freezing, following the product instructions.
Do not seal weep holes or drainage channels in modern frames, and do not caulk a window shut if it is needed as a fire escape — bedrooms and basements in particular must keep at least one operable exit window. For sash windows, a specialist sash draught-proofing system with brushes in the staff beads and parting beads can seal the sliding channels while keeping the window operable, and it is often a better long-term fix than foam tape alone, though it takes more time to fit.
Window Film, Rope Caulk and Other One-Winter Draft Stoppers
Window insulation film is one of the most effective one-season DIY solutions for single-glazed older windows. A clear plastic film is taped to the inside of the frame and shrunk tight with a hairdryer, creating a pocket of still air that mimics a second pane. It cuts draughts and cold radiating from the glass noticeably, though it does mean that window cannot be opened until the film is removed in spring. It is ideal for windows you do not need to open in winter.
Rope caulk is a pressable, putty-like cord that can be pushed into gaps around a sash for the winter and peeled off in spring. It is ugly and not a permanent repair, but it is very effective for a window that will be sealed all winter, and it is a good option for renters who cannot make permanent changes. Draft snakes — fabric tubes filled with sand or batting — block draughts at the sill, but they only help at the bottom of the window, so they work best combined with weatherstripping higher up.
Thermal Curtains and Secondary Glazing for Cold Old Glass
Heavy thermal curtains help with cold glass, especially at night. When closed, they trap a layer of air between the curtain and the window, acting as a buffer against cold radiating from the pane. For the best effect, the curtain should extend beyond the frame on both sides and reach the floor or sill, so cold air cannot easily spill around the edges. Open curtains on sunny winter days to let solar gain in, and close them as soon as it gets dark.
Secondary glazing — a second pane fitted inside the existing window — is a more durable step for single-glazed and heritage windows where replacement is not allowed or not wanted. It can be a DIY acrylic panel for one winter, or a professionally fitted system with a proper frame. It reduces both draughts and noise, and it preserves the original window. It is more expensive than film, but unlike film it can be opened and reused for many winters if it is well made.
A Room-by-Room Winter Window Plan for an Older Home
Start with bedrooms and living rooms, because comfort there matters most at night and in the evening, then move to hallways and kitchens. Work window by window: lock and weatherstrip first, caulk the frame joint second, and add film or curtains third where the glass is single-glazed. Doing one room completely is better than half-sealing every window in the house, because a fully sealed room will feel noticeably warmer and will show you what the rest of the house could feel like.
Keep a simple note of what you fitted on each window and when. Weatherstripping and foam tape wear out, film needs replacing each winter, and exterior caulk needs checking each autumn. A ten-minute check each year — before the first cold snap, not during it — will catch flattened strips and cracked caulk while they are still easy to fix. That annual habit is what turns a one-winter improvement into a lasting reduction in draughts.
Find leaks on a windy day with your hand or an incense test, room by room.
Lock windows properly and clean sash channels before adding any seal.
Fit weatherstripping matched to each gap, then reseal the frame-to-wall joint outside.
Add window film for single glazing and thermal curtains for night-time cold.
Note what you fitted on each window and recheck it every autumn.
Old Window Draft Mistakes That Waste Time and Money
The most common mistake is sealing the inside of a window while ignoring a failed exterior joint, so wind still gets behind the frame. Another is using foam tape that is too thick, which stops the window closing and actually creates a new gap elsewhere. A third is sealing every window shut in a home that needs ventilation — even in winter, a home needs some controlled fresh air to avoid condensation and mould, so keep trickle vents open where they exist and do not seal a room's only exit window.
Condensation is a related warning sign. If sealing a window suddenly causes heavy condensation on the glass or mould on the reveal, the room may now be too airtight for its moisture level, especially in a bathroom or kitchen. In that case, improve ventilation in that room — open a window briefly each day, use an extractor fan, or keep a trickle vent open — rather than removing all the draught-proofing. Comfort and healthy air need to be balanced, not traded against each other.
Final Thoughts: Warmer Older Windows Without Replacing Them All
Older windows do not have to mean a cold house all winter. Find the leaks, lock and weatherstrip the sashes, seal the frame joints, and add film or curtains where the glass itself is cold. Done room by room, that sequence usually delivers a noticeable improvement in comfort for a modest cost and a weekend's work, and it buys time to plan proper repairs or replacement for the windows that truly need it. The windows that are rotten, fogged or structurally failed will still need professional attention — but the rest can be made far more comfortable with careful DIY draught-proofing.
Winter Window Draft FAQs for Older Homes
What is the cheapest way to stop window drafts in winter?
Locking the window properly and fitting correctly sized weatherstripping is usually cheapest and fastest. For single glazing, a window insulation film kit adds a large comfort gain for a small cost, though it is a one-season fix.
Does window film really work on old single-glazed windows?
Yes, for comfort. The film creates a pocket of still air that reduces both draughts and heat loss through the glass. It will not make a single-glazed window perform like a modern double-glazed unit, but most people notice the difference immediately.
Should I caulk windows shut for winter?
Only windows you do not need to open, and never a bedroom or basement exit window. Rope caulk is a better temporary option than permanent caulk for a window you will want to open again in spring.
Why do my windows get condensation after draught-proofing?
Sealing leaks reduces air exchange, so moisture from cooking, showering and breathing can build up. Improve ventilation in that room — use extractor fans, open a window briefly each day, or keep trickle vents open — rather than removing all draught-proofing.
When is it time to replace an old window instead of sealing it?
Replace or professionally repair a window if the frame is rotten, the sash is painted shut and cannot be freed safely, the sealed unit is fogged between the panes, or draughts persist after weatherstripping, caulking and film have all been fitted properly.
Can renters draught-proof old windows?
Yes, with reversible options: window film, rope caulk, draft snakes and thermal curtains usually do not alter the window permanently. Check your tenancy agreement first, and avoid permanent caulk or sash modifications without the landlord's permission.