Misted Double Glazing, Fixed at Glass Level
Blown units make a house look tired long before the frames are worn out. Where the frame is sound, only the glass needs to change.
A seal problem, not a window problem
A double glazed unit is two panes bonded to a spacer bar filled with desiccant. When the perimeter seal lets go, damp air gets in, the desiccant saturates and the cavity fogs. Nothing about the frame has failed — which is why replacing whole windows for misting is usually the wrong spend.
We survey the whole elevation rather than the one window you called about, because units installed on the same day tend to fail within the same few years of each other.
How we work through it
1. Confirm it's a blown unit
Moisture you can't wipe away means the glass has failed, not the room. We check that first so you aren't paying to solve a ventilation problem with glass.
2. Measure and check the frame
We measure the sight size, check the drainage slots are clear and inspect the beading and gaskets that hold the unit — they decide whether glass alone is enough.
3. Order the unit to size
Each unit is made to the measured size and specification, including any upgrade to warm-edge spacer or A-rated glass.
4. Swap and re-bead
The failed unit comes out, the rebate is cleaned, the new unit is packed and re-beaded, and the frame drainage is cleared before we leave.
When replacement is the better call
- The frame has distorted and the unit no longer sits square in the rebate
- Drainage slots are blocked beyond clearing and units sit in standing water
- Several units on one elevation have gone within a short period
- The hardware is obsolete and replacement parts are no longer made
If that's your situation, the honest route is window replacement, and we'll quote both so you can compare.
Town-by-town misting guides
Common questions
- Can misted double glazing be fixed without replacing the whole window?
- In most cases yes. Misting sits inside the sealed unit, so where the frame, hinges and locks are sound we swap only the glass and leave the frame in place.
- Why has only one window misted up?
- Sealed units fail individually. South-facing and coastal elevations cycle hot and cold hardest, so those units usually go first even when the rest of the house is fine.
- Should I upgrade the glass while it's out?
- It's the cheapest moment to do it. The labour is already being paid for, so moving to a warm-edge, argon-filled A-rated unit only costs the difference in the glass.
- How long does a sealed unit swap take?
- Once the replacement unit has been made to size, the swap itself is usually a single short visit per window with no internal disruption.
Double glazing unit replacement explained
Why double glazing mists up
A double glazing unit is two panes of glass sealed around the edge with a spacer between them. When that seal fails, damp air gets into the gap and condenses on the inside faces of the glass, which is why misted or foggy double glazing cannot be wiped clean from either side. Condensation on the room-side face is different: that is moisture in the house, not a failed unit.
Read more: Misted windows: condensation causes
Replacement glass units on the existing frame
If the frame is sound, only the sealed unit needs replacing. We measure the unit, have a new one made to size and fit it into the existing frame, with new beads or gaskets where needed. The frame, hinges and handles stay as they are, so the work is quick and tidy compared with a new window.
Replacement units can be specified as A-rated glazing, and obscure or toughened glass where the position needs it.
- Misted, foggy or blown units replaced
- New unit made to fit your existing frame
- Obscure or toughened glass where required
- Worn hinges or handles replaced at the same visit
When the whole window should go
If several units have failed at once, the frames are warped or the windows are old and draughty, replacing the windows can be better value than replacing units one by one. We will say which applies at the survey.
Read more: Repair or replace? · uPVC window repairs · Replacement windows
More questions
Can misted double glazing be fixed without a new window?
Yes. If the frame is sound, we replace just the sealed glass unit with a new one made to fit the existing frame.
Why can't I wipe the mist off my windows?
If the mist is between the panes, the unit's edge seal has failed and moisture is trapped inside. Only a replacement unit will clear it.
Do you replace misted units in Dorset, such as Ferndown?
Yes. We cover Devon, Cornwall, Dorset and Somerset, including Ferndown, for misted double glazing unit replacement.
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