How to stop window draughts — what works and what doesn't

Light a candle and run it slowly around the frame perimeter on a windy day. Where the flame flickers, that's where the air is coming through.

Around the opening sash perimeter = gasket or hinge problem.

Around the glass-to-frame joint = sealant failure (rare) or unit failure.

From the glass itself feeling cold = sealed unit has lost gas fill or seal has failed.

If the rubber gasket has hardened or shrunk it won't compress properly. Replacement gasket is cheap (£20–£40 for a whole window) and a 30-minute job. This fixes 60% of draught complaints we see.

uPVC and composite window hinges have an adjustment screw that pulls the sash tighter into the frame. Over 10–15 years sashes drop slightly and need re-adjusting. We do this free for any windows we've fitted.

If the unit itself is misted, has visible condensation between the panes, or feels cold to the touch in winter, the argon fill has escaped and the unit has failed. Replacement sealed units in the same frame cost £150–£300 fitted depending on size.

If the frame itself has warped, rotted (in timber) or developed gaps at the brickwork, no amount of gasket replacement will fix the draught. At that point full window replacement is the right answer.