5 min read
Condensation between the panes is the single most common call we get. It looks like the window is finished, but usually it isn't — and the fix is far cheaper than most people expect.
Why it happens
A double glazed unit is two panes bonded to a spacer bar with a desiccant inside and a sealed edge. Heat, UV and years of expansion and contraction eventually break that edge seal. Once it's gone, moist air gets in, the desiccant saturates, and water vapour condenses between the panes where you can't reach it.
The frame itself is rarely the problem — it's the glass unit that's failed.
Does 'defogging' work?
You'll see companies advertising drilling and drying treatments. They can clear the mist temporarily, but they don't restore the edge seal and they don't replace the lost insulating gas. The unit stays a failed unit, the misting usually returns, and you've paid twice. We don't offer it.
What replacement actually involves
We measure the failed unit and the glazing bead, order the glass to size, and come back to swap it. The old unit comes out, the new one goes in on fresh packers, and the beads go back. Around 20 minutes per window once the glass is on site, and there's no disruption to the frame, plaster or décor.
Guide price is usually £90–£180 per standard unit fitted, depending on size and glass spec. Toughened, laminated, obscure and acoustic units cost more.
When you should replace the whole window
Replacement rather than repair makes sense if:
- •The frame is warped, cracked or the welds have opened
- •Hinges, gearboxes or handles are obsolete and no longer available
- •The window is single-glazed or very early double glazing with poor thermal performance
- •Multiple units in the same frame have failed and the window is 25+ years old
Can you upgrade the glass at the same time?
Yes — and it's the best moment to do it. Since the unit is being made to order anyway, you can move up to a warmer low-E unit, acoustic glass if you're on a main road, laminated glass for security, or obscure glass for a bathroom, for a modest extra cost.
FAQs
Can I claim on insurance for misted glass?
Not usually — seal failure is wear and tear, not accidental damage. Breakage is a different matter and is often covered.
How long does replacement glass take to arrive?
Standard units are typically a few days to a week; specialist glass can take a little longer.
Do you replace units in windows you didn't fit?
Yes, all makes of uPVC, aluminium and timber frames.