Sealed unit replacement
When the glass has misted between the panes, the sealed unit has failed and the frame is usually fine. Replacing only the unit is the cheapest fix, and it is the job where the quotes I see vary most, because a unit is made to measure and the price on the day depends on how the firm charges for the visit.
Is a sealed unit replacement right for your home?
Suits
- Windows with mist, droplets or a milky film trapped between the panes
- Frames that are sound, whether uPVC, aluminium or timber
- Owners who want the glass cured without paying for a whole new window
Good points
- Far cheaper than replacing the whole window when the frame is in good order
- The frame, hinges and handles stay in place, so there is little mess
- A unit swap usually takes about an hour once the new unit has arrived
Watch out for
- The unit is made to measure, so there are normally two visits, a survey and a fitting
- A minimum call-out charge can make one unit cost nearly as much as two
- If the seals or the frame are failing, a new unit will mist again early
What a sealed unit replacement costs
A sealed unit replacement typically costs £170 (one failed sealed unit in a standard casement window, supplied and fitted into the existing frame), with most jobs between £50 and £400. That includes VAT at 20%. Fitting takes 1–2 hours on site.
What you would actually pay
Typical one failed sealed unit in a standard casement window, supplied and fitted into the existing frame · UK- Typical installed cost Sealed unit replacement, supplied and fitted
- £142
- VAT at 20% Standard rate
- £28
- Net cost to you
- £170
If you borrowed £170.00 over 36 months at 0.0%, it would cost £4.72 a month – £170.00 in total, of which £0.00 is interest. The last payment would be £4.80.
Illustration only – not a quote, not an offer of credit, and not financial advice. Rates depend on your circumstances and creditworthiness.
Where the money goes on sealed unit replacement
| Element | Typical range |
|---|---|
| Call-out minimum Most fitters charge a minimum for the visit, and it normally covers the first unit. Extra units on the same visit are then much cheaper. | £80 – £150 |
| Sealed unit and fitting, per unit A made-to-measure sealed unit for a standard casement, fitted into the existing frame with new seals. | £100 – £200 |
| Upper-floor access Units above the ground floor that need ladders or a tower take longer and sometimes need a second visit. | £30 – £100 |
Guide prices including VAT. Your actual cost depends on your home, access and specification.
What moves the price of sealed unit replacement
- Size of the unit
A small pane costs a fraction of a large picture window. Toughened glass for a patio door costs more again.
- Glass specification
Plain clear glass is the base. Toughened, laminated, obscure and low-emissivity glass all cost more, and the unit has to match what the rules require in that position.
- How many units
The call-out is paid once, so replacing every failed unit in one visit is usually far better value than coming back for each.
- The frame it goes into
A modern uPVC frame takes a new unit easily. An old timber frame may need its beads, putty or seals redone, and a worn frame can add to the work.
- Access
Upstairs units, or any window that cannot be reached from the ground, take longer and may need a tower.
What should be in a quote for sealed unit replacement
If a quote is missing any of these, ask why before you compare it with another.
- The size of each sealed unit, measured by the fitter and written on the quote
- The glass specification: the thickness of each pane, the gap, the gas fill and whether it is toughened or obscure
- Whether the frame, seals and beads are being checked or replaced, or only the unit
- Whether it is one visit or two, and when the new unit will arrive
- The call-out or minimum charge, and what it covers
- The guarantee on the new unit, in writing, and who stands behind it
Sealed unit replacement prices by region
Labour is most of the difference. Typical price (one failed sealed unit in a standard casement window, supplied and fitted into the existing frame), including VAT.
| Region | Typical | vs UK average |
|---|---|---|
| London | £220 | +25% |
| South East | £200 | +17% |
| South West | £190 | +10% |
| East of England | £180 | +6% |
| West Midlands | £180 | +4% |
| Scotland | £180 | +2% |
| East Midlands | £170 | UK average |
| Yorkshire and the Humber | £170 | UK average |
| North West | £170 | −2% |
| North East | £170 | −5% |
| Wales | £160 | −6% |
| Northern Ireland | £150 | −12% |
Common questions
Is it worth replacing just the glass unit?
When the frame is sound, yes. A new unit costs a fraction of a new window. If the frame is rotten, warped or its seals have perished, the new unit tends to fail early, and replacing the window is the honest advice.
Can misted glass be cleaned or demisted instead?
A demisting service drills the unit and vents it, which clears the visible mist for a while. The seal has still failed and the gas has gone, so most units mist again. I treat it as a cosmetic stopgap, not a repair.
Why do I have to wait for a second visit?
Sealed units are made to measure, so the fitter has to measure up, order the unit and come back when it arrives. A firm that promises a unit the same day is either carrying stock for a standard size or has not measured properly.
Does home insurance cover a misted unit?
Usually not. Insurers cover sudden events such as impact, storm or break-ins, not wear and tear such as a failed seal. Check the excess before claiming on anything, because it can be more than the repair.
Where the sealed unit replacement prices come from
We store each price without VAT and add it back for display. These are the published guides behind the figures:
- BestBuilders, blown window repair cost UK, last updated 5 September 2026: standard casement unit supply and fit, with call-out minimum and upper-floor access rows; VAT treatment not stated, so treated as VAT-inclusive and divided by 1.2 to store ex-VAT
- MyJobQuote, blown double glazing repair cost, last updated 22 September 2026: single replacement unit by size, labour included; VAT treatment not stated, so treated as VAT-inclusive and divided by 1.2 to store ex-VAT
- MyBuilder, how much does double glazing repair cost: misted unit repair from small to large units; VAT treatment not stated, so treated as VAT-inclusive and divided by 1.2 to store ex-VAT. The widest of the three sources
- ExpertSure, double glazing repairs cost, prices verified October 2026: its sealed-unit figures are taken from MyJobQuote, so it is a cross-check only and is not used in the range
- HMRC VAT Notice 708/6: glazing is not an energy-saving material, so the standard rate applies
Get quotes for your home
A guide price only takes you so far. Local firms can price the work on your own home, and comparing a few quotes is the quickest way to see what is reasonable.
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