Double glazing doesn’t fail overnight — it fades slowly. Your home just starts feeling colder, noisier or draughtier than it used to, and it’s easy to put off doing anything about it. But worn-out windows quietly cost you money every month in wasted heat. If you’re wondering whether it’s time to replace your double glazing, here are seven clear signs to look out for.
1. Condensation or misting between the panes
This is the most obvious red flag. If you can see fog, moisture or even water droplets between the two panes of glass — not just on the inside surface — the sealed unit has failed. Once that airtight seal breaks, the window loses most of its insulating power and no amount of wiping will clear it. This one almost always means replacement.
2. Draughts around the frames
Stand near your windows on a windy day. If you can feel cold air sneaking in around the edges, the seals or frames have deteriorated. Draughty windows force your heating to work harder and are one of the quickest ways to lose warmth from a room.
3. Rising energy bills
If your heating costs keep climbing despite no change in how you use your home, tired windows are often the culprit. Modern A-rated double glazing can save up to £175 a year on heating compared with single glazing — older or failing units leak that saving straight out of the house.
4. More outside noise than there used to be
Good double glazing should noticeably soften traffic, neighbours and street noise. If your home feels louder than it once did, the units may have lost their acoustic seal. Newer glazing (and triple glazing in particular) can make a dramatic difference for homes near busy roads.
5. Windows that stick, jam or won’t lock properly
Frames that have warped, dropped or swollen make windows hard to open, close or lock. Beyond the daily annoyance, a window that won’t lock securely is a genuine security weak point — and a sign the hardware and frame are past their best.
6. Visible damage, rot or discolouration
Cracked glass, crumbling seals, rotting timber or yellowing uPVC are all signs of age. Cosmetic damage often hints at deeper problems with the frame’s structure and weatherproofing, and it drags down your home’s kerb appeal too.
7. Your windows are simply old
Most double glazing has a working lifespan of around 20–25 years for uPVC, and a little longer for aluminium and well-maintained timber. If your windows are pushing two decades, they’re likely well behind today’s energy-efficiency standards — even if they look okay at a glance.
Should you repair or replace?
A single failed handle, hinge or seal can sometimes be repaired. But once you’re seeing misted panes, multiple draughts or several of the signs above at once, replacement is usually the smarter long-term choice — you’ll claw back the outlay through lower bills, better comfort and added property value. Curious what new windows would set you back? See our full guide to the cost of new windows.
Get a free, no-pressure assessment
Not sure whether yours need replacing? As FENSA-registered double glazing experts, we’ll take a proper look and give you honest advice — repair if that’s all you need, replace if it’s truly worth it. Request your free quote today and we’ll help you make the right call for your home.
