Blown window repair Cost Calculator
A blown window — condensation trapped between the panes — means the sealed unit has failed, not the window. Replacing just the glass unit costs £75–£250 fitted for most casements, rising to £200–£450 for toughened patio-door glass. The frames stay…
Open the calculator →Price blown window repair in 30 seconds
3 steps, using the figures from our cost guide.
How this calculator works
Every figure in this calculator is the one published in the cost table on our blown window repair guide. Pick the option that matches your job and the calculator returns that published range, adjusted for your region - it does not model anything the guide does not already say.
That is deliberate. A calculator whose rates drift from the page it sits under is worse than no calculator, because two numbers on the same site disagree.
What it cannot know: access, the condition of what is already there, and anything structural. Those are what separate three real quotes from each other.
Published blown window repair costs (2026)
| Option | Typical 2026 cost | Notes |
|---|---|---|
| Small casement unit (to ~0.5m² | £75–£150 | |
| Standard casement unit | £100–£200 | |
| Large fixed / picture unit | £150–£300 | |
| Patio door glass (toughened) | £200–£450 | |
| Bay window (3–5 units) | £300–£850 | |
| Whole-house refresh (8–12 un | £700–£1,900 |
These are the figures from our blown window repair cost guide.
Blown window repair calculator — FAQs
A double-glazed sealed unit whose edge seal has failed. The desiccant in the spacer bar saturates, moisture creeps between the panes and shows as misting or droplets you cannot wipe off. The glass unit needs replacing; the window itself usually does not.
“Demisting” services drill the unit and vent or flush it for £60–£120. It clears the visible mist for a while, but the seal is still failed and the insulating gas is long gone — most units mist again. Treat it as a cosmetic stopgap, not a repair.
When the frames are sound, yes — a unit swap typically costs £75–£250 against £400–£1,800 for a full new window. When gaskets are perished or frames warped, the new unit will fail early and full replacement is the honest advice.
Two visits: one to measure, then about an hour per unit to fit once the made-to-measure units arrive — usually one to two weeks later. Beads are removed, the unit swapped and the window back in use the same hour.
Related cost guides
- Blown window repair cost guide — The full price guide
- All double glazing services — Browse the hub
- All BestBuilders services — Every trade we cover
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