A draught is the most honest fault a window can have. You can feel exactly where your heating money is going, in real time, on the back of your neck. And because the sensation is so specific, draughts are unusually easy to diagnose. A few minutes with a candle or an incense stick maps the leaks, and where the leak sits tells you both the cause and roughly what it'll cost to put right.
Here's the map, from free fixes through to the honest replacement conversation.
First, find the leak precisely
Pick a breezy day and move a candle flame or incense stick slowly around the window. Trace the sash-to-frame junction, the glass beading, the frame-to-wall perimeter, the trickle vent, the handle and the hinge points, and watch where the flame dances. Whichever junction leaks is your diagnosis. One distinction matters here. Moving air is a true draught, air actually passing through. Cold falling air is convection rolling off a chilly pane, and no amount of sealing will fix it because nothing is leaking. That one's a glazing-performance issue.
Leak at the sash edges: gaskets and compression
The rubber gaskets sealing sash to frame harden, shrink and crack with age. On windows past 15 years old they're the most common draught source, and shrunken corners with visible gaps confirm it. Try the fixes in this order. First, adjust the hinges or locking cams so the sash pulls tighter onto its seals; many mushroom-cam locks adjust with a single turn. Next, replace the gasket itself. Gasket costs little per metre and an engineer can re-gasket a window quickly. In the meantime, self-adhesive draught strip is a perfectly honourable stopgap.
Leak at the frame perimeter: the installation gap
Air moving between frame and wall means the perimeter seal has failed. Either the old silicone has cracked away, or the original installation was foamed carelessly and never sealed properly in the first place. Outside, rake out the failed sealant and run a fresh bead, or have it done; it's an hour's work per window. Inside, persistent perimeter draughts on a newer installation are a fitting-quality complaint worth raising with your installer. Don't sit on this one, either. Perimeter leaks let water in as well as air, so they escalate from a comfort problem to fabric damage if ignored.
Leak through the 'closed' vent, keyhole or hardware
- Trickle vents whistle when they're worn or cheap. Replace them with modern baffled (or acoustic) vents rather than taping them shut, because a sealed vent just swaps a draught for condensation and mould
- Espagnolette handles and old keyholes leak a little; a worn handle mechanism that doesn't pull the sash home is really a compression fault in disguise
- A sash that rattles in the wind isn't sealing at all. Adjust the keeps and cams first, and if adjustment can't close the gap, the frame or sash has moved, which is a structural symptom worth noting
The false draught: cold pouring off the glass
Flame steady, but you still feel cold by the window? That's convection. Old or failed glazing chills the air next to it, which sinks and flows across the room exactly like a leak. No strip or sealant will help, because the 'draught' is the glass itself underperforming: single glazing, or double glazing whose gas fill and coatings gave up years ago. The cures are glazing cures, either modern Low-E units into sound frames, or replacement where the frames are finished too. Heavy curtains help you feel warmer; the heat-loss arithmetic explains why they don't do much for the bill.
Patch or replace: the honest threshold
Patch when the frame is sound and the leaks are specific. Gaskets, sealant runs and hardware adjustment are cheap, effective jobs our repair team does daily. Replace when draughts turn up as one symptom among several, alongside misted units, warped or brittle frames and hardware that no longer adjusts, because sealing one leak on a failing window is bailing a boat with a sponge. You'll find the full symptom checklist in 10 signs you need new windows. As a rule of thumb, money spent repeatedly re-sealing a 25-year-old window is money subtracted from its inevitable replacement.
This winter, in order
- Map every window with the flame test on one breezy afternoon; fifteen minutes covers the whole house
- Do the free fixes first: adjust cams and hinges, and clear or close anything that should close
- Re-gasket and re-seal the fixable windows before the cold properly sets in
- Strip-seal the doomed windows as triage, and plan their replacement to your timetable rather than the window's
- Book whole-house replacement surveys by autumn at the latest, because the first cold week fills every fitter's diary in the region
One habit turns all of this from crisis response into routine. Put the flame test in your calendar for the first blustery weekend of October, right next to bleeding the radiators. Draughts caught in autumn are gaskets and sealant. Draughts endured until February are higher bills, damp reveals and a rushed decision in the industry's busiest month. Windows reward owners who check on them once a year. So, noticeably, does the heating bill.
Frequently asked questions
Why are my double glazed windows draughty?
Usually perished sash gaskets, dropped hinges that reduce seal compression, or failed perimeter sealant, all repairable while the frame is sound. If the air feels cold but still, that's convection off underperforming glass rather than a leak: a glazing problem, not a sealing one.
What's the cheapest way to fix a draughty window?
Free: adjust the locking cams and hinges so the sash compresses its seals properly. Cheap: new gaskets and a fresh bead of perimeter sealant. Self-adhesive foam strip is a reasonable stopgap but a poor permanent answer.
Should I seal up my trickle vents to stop draughts?
No. They're your background ventilation, and sealing them invites condensation and mould. If a vent whistles or over-ventilates, replace it with a modern baffled design that lets air through without the gale.
Do draught excluders and window film work?
As winter triage on windows awaiting replacement, yes. Film adds a still-air layer and strips close the gaps. Neither touches the underlying fault, though, and on decent windows they're treating a symptom that a £5 gasket or a quick adjustment would cure properly.
How much heat do draughty windows actually lose?
Air leakage can add meaningfully to a window's losses; a leaky old window loses heat through its glass and around its seals at the same time. Sealing the leaks is the fastest payback in glazing, and upgrading the glass is the deeper fix.
When is a draughty window not worth repairing?
When the draughts arrive alongside misted units, brittle or warped frames and hardware at the end of its adjustment range. That cluster marks end of life. Re-sealing such windows buys you months; replacement resets the clock for decades.
Map the draughts, then call us
We re-gasket, re-seal and adjust whatever's worth saving, and we'll quote honestly when it isn't. Repairs and A++ replacements across Greater Manchester from our Trafford Park factory, all guaranteed for 10 years.
Call 07533 830717, WhatsApp us a photo for a fast quote, or request a free quote online.