You’ve spotted it. That foggy patch sitting between the panes — the one you can’t wipe away no matter what you try. Or perhaps it’s the draught you’ve started feeling on your hand every time you sit near the window. Or a crack that appeared overnight after a cold snap.
The moment you notice it, the same thought hits almost everyone: how much is this going to cost me?
Here’s the honest answer: in the vast majority of cases, far less than you’re expecting. Most double glazing Problems don’t mean new windows. They mean a blown sealed unit — a glass-only fix that takes under an hour and typically costs between £60 and £120. But not always. And knowing which situation you’re in is exactly what this guide is for. We’ll walk you through every common problem, give you a clear repair-or-replace decision framework, and share honest 2026 prices for the High Wycombe, Oxford and Reading area — no jargon, no upselling.
What’s Actually Wrong? The Three Most Common Double Glazing Problems
Before you can decide whether to repair or replace, you need to know what you’re actually dealing with. Most calls The Glazing Squad receive fall into one of three categories. Here’s how to identify yours.
1. Misted or foggy glass — the sealed unit has blown
This is the most common call we receive — particularly across High wycombe, Oxford and Reading, where a large proportion of homes were built between the 1970s and the mid-1990s. Original glazing from that era is now sitting right at, or well beyond, its 20 to 25-year lifespan.
What’s happening inside the window: the factory-sealed unit is made of two panes of glass bonded together with a spacer bar and an airtight perimeter seal, with argon gas trapped in the cavity between them. When that seal fails — through age, expansion and contraction, or impact — the argon escapes and moisture-laden air rushes in. As temperatures drop, that moisture condenses on the inner glass surfaces. The result is the foggy, cloudy appearance you can’t wipe away from either side, because it’s sealed inside the unit.
The critical thing to understand: this is a glass unit problem, not a frame problem. In most cases, the UPVC or aluminium frame around it is completely fine. You don’t need new windows. You need the failed glass unit replaced — and that’s a very different job.
2. Cold draughts – the seals or gaskets around the frame have failed
This is a different problem entirely. Run your bare hand slowly around the edge of the glass where it meets the frame on a cold day. If you feel cold air moving, the rubber gasket or seal around the perimeter has degraded. Over time, these rubber seals harden, shrink and crack.
The good news: gasket seal replacement is usually the most affordable repair on this list. The frame itself is fine. A glazier replaces the rubber bead, and the draught stops. It doesn’t mean the sealed unit inside has failed — though if the window is older, it’s worth having both checked at the same time.
3. Cracked or broken glass — a safety and security issue; act quickly
A cracked or smashed pane is never just cosmetic. Depending on the location, it’s both a security risk — your home is easier to access — and potentially a safety risk if the glass is in a door or low-level window. Don’t leave it.
Should You Repair or Replace? Here’s the Honest Answer
This is the question everyone reading this page actually wants answered. So let’s get straight to it. The decision comes down to one thing: is it the glass that’s failed, or the frame?
If the frame — the UPVC, aluminium or timber surround — is solid, undamaged and sealing properly, almost
all double glazing problems are repair jobs. A new sealed unit is manufactured to the exact measurements of
your existing frame, fitted inside it, and the job is done. Your frames stay. Your costs stay low.
f the frame itself is warped, cracked, soft to the touch, or showing rot, then even a perfect new glass unit will
fail again — because the frame can no longer hold a proper seal. That’s when replacement becomes the right
call.
One local context worth knowing: a significant proportion of homes across High Wycombe, Aylesbury and the
wider Chilterns were built between the 1970s and 1995. Double glazing installed during that period is now
between 30 and 50 years old — well past its rated lifespan. If your home is from this era and you’re seeing
several windows misting at the same time, it’s worth discussing full replacement rather than patching units one
by one. We’ll always give you the honest assessment
5 Signs Your Double Glazing Needs Replacing, Not Repairing
Repair is almost always the right answer when only the glass unit has failed. But there are specific situations where full replacement is the smarter long-term investment. Here are the five signs to look for.
1. The frame itself is warped, soft or cracked. Press your thumb gently along the frame. If the UPVC gives, feels spongy, or has visible cracking, the structure is compromised. A new sealed unit won’t seal properly inside a failing frame — you’d be spending money for a temporary fix at best.
2. You’ve had the same window repaired before and it’s failed again. A recurring failure on the same unit usually means the frame seal has degraded to the point where it can no longer hold a new unit properly. The unit keeps failing because the root cause — the frame — hasn’t been addressed.
3. Multiple windows are misting at the same time. When three, four or five windows all fail within the same season, it’s a clear age-related signal. The whole installation has reached the end of its life together. Patching them one by one costs more over three years than a full replacement done once — and you lose the energy efficiency gains of a modern A-rated installation
4. The window won’t open, close or lock properly. Mechanism failure combined with seal failure usually means the frame has moved or warped beyond repair. A window that doesn’t lock is also a security issue — don’t leave it unresolved.
5. Your home was built before 1995 and still has its original glazing. That glazing is at least 30 years old. The rated lifespan of a well-installed sealed unit is 20 to 25 years. Replacement at this stage gives you modern low-E glass, a better EPC rating, lower heating bills, and a new FENSA certificate — which matters if you ever sell.
Not sure which camp you’re in? Send us a photo on WhatsApp and we’ll give you an honest assessment before you commit to anything. Call 0800 699 0908 or WhatsApp us directly
FAQ
Q1. Can you repair misted double glazing without replacing the whole window?
Yes — in the vast majority of cases. When the sealed glass unit fails, it can be replaced completely independently of the frame around it. The new unit is manufactured to the exact dimensions of your existing frame and fitted directly into it. Full window replacement is only necessary when the frame itself is damaged, warped, or beyond repair.
Q2. How long does it take to replace a blown double glazed unit?
A single sealed unit replacement typically takes between 45 minutes and one hour. We visit first to measure, order the unit to your exact specifications, and return to fit it — usually within a few days. If multiple units are being replaced in one visit, most jobs are finished within a morning.
Q3. Why has my double glazing gone misty on the inside between the panes?
The misting between the panes is condensation trapped inside the sealed unit. It appears because the factory seal has failed — the insulating gas has escaped and moist air has entered. You can’t wipe it away from either side because it’s locked inside the unit. The only lasting fix is to replace the affected glass unit.
Q4. Does home insurance cover misted double glazing?
Most standard home insurance policies do not cover seal failure caused by age and general wear. However, if your glazing failed as a result of an insured event — storm damage, a break-in, or accidental impact — your insurer should cover the repair. The Glazing Squad are insurance-approved and can liaise directly with your insurer on your behalf.
