How to draught-proof windows

Inspired by a helpful YouTube guide. This walk-through draws on the video "How to Draught Proof Your Windows" by Hiatt Hardware, a UK trade hardware supplier whose practical how-to videos cover exactly the kind of straightforward home improvement jobs that save money and make a real difference to comfort.

1. Find where the draughts are coming from

Before you buy anything, work out where the cold air is actually getting in. Hold a lit incense stick or a thin strip of tissue paper near the window frame on a windy day. Anywhere the smoke or paper wavers, air is getting through.

The most common culprits are the gap between the opening sash and the frame, the gap at the top and bottom of sash windows, and cracked or shrunken silicone around the outer frame. Check all of them. There is no point sealing one gap if air is coming through another.

2. Choose the right type of seal

Different gaps need different products. Self-adhesive foam strips work well on casement windows - they compress as the window closes and form a reliable seal. For sash windows, a V-seal or brush strip is better because it can cope with the sliding motion without wearing away quickly.

For fixed gaps around the outer frame - between the window frame and the masonry - silicone sealant is the right answer. That is a different job from sealing the opening parts. Mind you, both can be done in the same afternoon if the gaps are obvious.

3. Clean the surfaces before fitting anything

Self-adhesive strips will not stick properly to a dirty or greasy surface. Wipe down the rebate - the channel the opening sash closes into - with a damp cloth, then dry it thoroughly. If the surface is painted and flaking, rub it back with a bit of sandpaper first.

Cold temperatures reduce adhesion, so do this job on a dry day when the temperature is above 10°C if you can. Most adhesive sealers need a few hours to cure properly before the window is closed hard against them.

4. Fit self-adhesive foam or rubber strips

Measure the length of each rebate, cut the strip to size with scissors, and peel off the backing. Press it firmly into place, working along the frame in one continuous run. Overlap corners slightly rather than cutting mitres - it gives a better seal with less fuss.

When you close the window, the strip should compress but not be squashed flat. If it is, you have used too thick a profile. To be fair, most foam strip packs come in a couple of thicknesses - it is worth checking the gap size before you buy rather than guessing.

5. Fit a V-seal strip for sliding sash windows

V-seal strip - sometimes called weatherstrip - is a folded plastic strip that springs open to fill a gap. For sash windows, it is fitted into the channel the sash slides in, with the open side of the V facing outwards into the gap.

Peel the backing and press it into the channel from top to bottom. Trim to length with scissors. The strip should sit flush when the window is closed and spring back into shape when it opens. It handles repeated sliding better than foam and will last several years.

6. Renew any cracked silicone around the outer frame

If the existing silicone between the frame and the wall has cracked, pulled away, or gone hard and brittle, rake it out with a flat-head screwdriver or a dedicated silicone remover tool. Clean the surface, then apply a fresh bead of exterior-grade silicone, smoothing it with a wet finger or a caulk tool.

Leave it to cure for 24 hours before exposing it to rain. That said, a tidy silicone bead is one of those jobs that looks a lot better than it has any right to given how little effort it takes.

When to call a handyman

Draught-proofing is well within DIY reach for most people. Where a handyman is useful is when the frames themselves are rotten, the window no longer closes squarely, or there are multiple windows to tackle at once and you would rather get it done in an afternoon than spread the work across several weekends.