That cold line of air around the window frame is more than a small annoyance. It can make a room feel chilly even when the heating is on, encourage condensation and leave you turning the thermostat up just to feel comfortable. Learning how to seal draughty windows is one of the quickest, most affordable jobs you can tackle before colder weather sets in.

The good news is that most draughts come from gaps that are easy to find and straightforward to deal with. The right fix depends on whether the air is coming through an opening sash, around the frame, through the glass, or from a damaged seal outside. Start with a proper check, then choose the simplest solution that suits your window and home.

Find where the draught is coming from

Before buying anything, work out exactly where air is getting in. On a windy day, slowly move the back of your hand around the edges of the window, particularly where the opening section meets the frame. You may feel a clear cold current around the top, sides, bottom or locking edge.

A lit incense stick can also help, as the smoke will move when it reaches a draught. Take care around curtains, blinds and anything flammable. Do not use this method near a gas appliance or if you are concerned about ventilation.

Check these common trouble spots:

Gaps between an opening window and its frame
Worn, flattened or missing rubber seals
Cracks around the frame where it meets the wall
Loose putty or failed sealant around glazing
Gaps around the sill, handles or locks

Not every bit of airflow is a fault. Many modern windows have trickle vents, usually at the top of the frame, designed to provide background ventilation. Do not permanently block them. Good ventilation helps reduce damp and condensation, particularly in kitchens, bathrooms and bedrooms.

How to seal draughty windows with strips

For small gaps around opening windows, self-adhesive draught-excluder strips are often the easiest place to start. They are available in foam, rubber and brush styles. Foam is inexpensive and suits light, uneven gaps, while rubber or silicone strips tend to last longer and give a neater, more durable seal.

First, clean and dry the contact surface thoroughly. Dust, old adhesive and condensation can stop a strip from sticking properly. Measure each section of the frame, cut the strip to size and apply it where the opening window closes against the frame. Avoid fitting it so thickly that the handle becomes difficult to lock or the sash will not shut.

Close the window and test it afterwards. If it closes smoothly and the cold air has stopped, you have the right fit. If you have to force it shut, remove the strip and use a thinner profile. A seal should close a gap, not put pressure on hinges, catches or the glass.

Brush strips are especially useful for sliding sash windows and some older designs where the surfaces move against each other. They help reduce air movement without preventing the window from operating. For a rented flat, removable draught strips are usually a sensible first choice because they are low-cost and cause minimal alteration.

Seal gaps around the frame

If the draught is coming from between the window frame and the surrounding wall, an interior decorator’s caulk is often suitable for fine cracks. It can be smoothed with a damp finger or finishing tool, then painted once dry. Use it on stable, narrow gaps indoors, not on moving joints.

For exterior gaps, use a weatherproof exterior-grade sealant that is made for windows and masonry. This is where the choice matters. Indoor caulk is not designed to cope with rain, frost and changing temperatures, while the wrong exterior product may crack or peel away over time.

Remove loose, crumbling old sealant before applying a fresh bead. The area needs to be clean and dry, and it is worth checking the weather forecast before starting. Sealant applied in persistent rain or on a wet surface is unlikely to last.

Take care not to cover drainage holes in uPVC frames. These small openings allow water to escape from the frame and should remain clear. Blocking them can lead to water collecting where you do not want it.

Older timber windows need a different approach

Traditional timber windows can be full of character, but decades of movement, paint build-up and changing weather can create gaps. Draught-proofing strips work well on many wooden casement windows, but first check that the frame is sound. Soft timber, peeling paint, rot or loose joints need attention before sealing.

For sash windows, a specialist draught-proofing system can be worthwhile if the windows are otherwise in good condition. These can include slim brush seals set into the meeting rails and channels. They cost more than stick-on foam, but they preserve the look and operation of the window far better than a temporary fix.

Do not seal a window painted shut just to stop a draught. It may be tempting in a rarely used room, but windows can be needed for ventilation and as an emergency exit. Repairing a sticking window and adding the correct seals is the safer long-term answer.

Deal with draughts around the glass

If air seems to be coming through the edge of a single-glazed pane, inspect the putty or glazing compound from outside. Cracked, missing or loose sections can let in cold air and water. Small repairs are manageable for confident DIYers, but loose glass or widespread failure is best dealt with by a glazier.

For single glazing, temporary secondary glazing film can make a noticeable difference during winter. It is a clear plastic film fixed to the inside of the frame with double-sided tape, then tightened carefully with warm air from a hairdryer. It creates an insulating air layer and can cut down on the cold feeling from the glass.

It is not a permanent replacement for double glazing, and it can be fiddly around frequently opened windows. Still, it is a useful budget-friendly option for spare rooms, period properties and rented homes where replacing windows is not possible.

With double-glazed units, condensation between the panes, a misty appearance that will not wipe away, or cold air from the glazed unit itself can point to a failed sealed unit. Surface seals and draught strips will not fix that. The glass unit may need replacing, though the whole frame does not necessarily have to be changed.

Do not forget curtains, blinds and window fittings

A well-fitted curtain can make a room feel warmer, especially at night, but it should support proper sealing rather than hide a problem. Close lined or thermal curtains after dark and make sure they reach near the sill or floor where practical. Keep them away from radiators, as trapping heat behind fabric stops warmth circulating through the room.

Cellular blinds can also reduce heat loss, particularly on large panes of glass. They are most effective when fitted close to the window recess. Neither blinds nor curtains stop a genuine gap around the frame, so deal with the draught first.

Loose handles and poorly adjusted locks can prevent a uPVC window from pulling tightly against its seals. If you can see daylight around a closed window or it rattles in the wind, the hinges, locks or keeps may need adjustment. Make only small adjustments and stop if the mechanism feels stiff. A local window repair specialist can often resolve this without the cost of a replacement window.

A quick order of jobs that saves time

Start with the simplest and most reversible fix. Clean the frame, replace worn draught strips and test the window closure. Next, fill fine cracks around the inside frame and inspect exterior sealant on a dry day. Then consider secondary glazing, curtains or blinds for extra comfort.

If the problem continues, look for signs that point beyond a simple draught: water stains, rotten timber, mould around the reveal, misted double glazing, broken hinges or gaps that keep returning. These issues need a repair rather than more sealant.

A few practical supplies kept at home can make this job easy to tackle when you spot a problem: draught-excluder strip, exterior sealant, decorator’s caulk, a sealant gun, a scraper and cleaning cloths. EasyPeasyMate.Shop is built around those useful everyday essentials that help small home jobs stay simple.

A properly sealed window should still open, lock and ventilate the room when needed. Aim for a home that holds onto its warmth without shutting out fresh air, and you will feel the difference long before the next cold snap.

How to Seal Draughty Windows and Keep Heat In