Glass and upgrades
Triple glazed sealed unit replacement
We are asked this a lot, so here is the straight answer: in most existing double glazed frames, swapping to triple glass is not worth it. A thin triple unit that fits the old rebate reaches only about U 1.2 at the centre of the glass, no better than modern double. Where a frame has a deep enough rebate, and the hinges can carry the weight, a full triple unit is possible, and we will check.
Summary
Sealed unit replacement means changing only the glass in an existing frame. Most UK double glazed frames take units up to about 28 mm thick, while a good triple unit is 36 to 44 mm, so a straight swap is often not possible; a thin 28 mm triple unit performs worse than a good double unit.
What you get
| Typical existing rebate | Units up to about 24 to 28 mm |
|---|---|
| Good triple unit | About 36 to 44 mm thick |
| Thin triple (28 mm) | About Ug 1.2: worse than good double glazing |
| Weight | About 50% heavier than a double unit |
| Also checked | Hinges, beads, drainage, frame condition |
| Typical lead time | 1 to 2 weeks for units |
Guide prices
Guide prices per sealed unit or window, fitted.
Small unit
up to about 0.6 m2, frame checked first
£145 – £195inc VAT · £120 – £160 ex VAT
- Triple unit made to measure
- Old unit removed and recycled
- New beads and glazing packers where needed
Medium unit
about 0.6 to 1.2 m2
£195 – £245inc VAT · £160 – £205 ex VAT
- Triple unit made to measure
- Old unit removed and recycled
- New beads and glazing packers where needed
Large unit
about 1.2 to 2 m2
£295 – £395inc VAT · £245 – £330 ex VAT
- Triple unit made to measure
- Old unit removed and recycled
- New beads and glazing packers where needed
Guide prices, supply and fit. The written quote after your survey fixes the price for the specification shown; anything extra is agreed with you first.
Is it right for your home?
A good fit for
- Frames with deep rebates that were designed for triple glass
- Replacing a failed triple unit
- Upgrading one or two fixed panes
Think twice if
- Standard 70 mm uPVC frames with 28 mm units
- Frames that are already worn or dropping
Options
- High-performance double units with warm edge, where triple will not fit
- Acoustic or laminated replacement units
- Obscure and decorative glass
- New beads and gaskets
- Hinge replacement
When a glass-only upgrade does make sense
If your frames were built for triple glazing, or have a deep enough rebate, a new triple unit can be fitted without changing the frame. The same applies to replacing a failed triple unit. Otherwise, a modern A-rated double unit with warm-edge spacers is usually the better buy for the frame you have.
Misted units
Condensation between the panes means the seal has failed. The unit needs replacing; the frame may be fine. We can replace failed units with the best unit your frame can take.
Building Regulations by nation
| Nation | Replacement windows | Sign-off |
|---|---|---|
| England | 1.4 W/m²K, or a Window Energy Rating of band B or better | Competent person scheme or building control |
| Wales | 1.4 W/m²K, or a Window Energy Rating of band B or better | Competent person scheme or building control |
| Scotland | 1.6 W/m²K | No building warrant for a straight replacement; must meet the standards |
| Northern Ireland | 1.6 W/m²K, or a Window Energy Rating of band C or better | No building notice for a straight replacement; must comply |
Full regulations guide, with sources →
Questions about glass-only replacement
Can I put triple glazing in my existing windows?
Usually not in a way that helps. Most frames take up to about 28 mm units; a triple unit that thin performs about the same as, or worse than, good double glazing. We check your frames before recommending anything.
How much does a triple glazed sealed unit cost?
Where a frame can take one, our guide starts at £145 fitted for a small unit, inc VAT. Published UK figures of about £90 to £220 per unit are mostly for double units; triple units cost more.
Why are my windows misting between the panes?
The seal around the unit has failed and moist air has got in. Only replacing the unit fixes it.
Will heavier glass damage my hinges?
It can. Triple units are about 50% heavier, so hinges and packers are checked and upgraded where needed.
Related products
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Learn more →Glass-only replacement by area
England
- Bedfordshire
- Berkshire
- Bristol
- Buckinghamshire
- Cambridgeshire
- Cheshire
- Cornwall
- County Durham
- Cumbria
- Derbyshire
- Devon
- Dorset
- East Riding of Yorkshire
- East Sussex
- Essex
- Gloucestershire
- Greater London
- Greater Manchester
- Hampshire
- Herefordshire
- Hertfordshire
- Isle of Wight
- Kent
- Lancashire
- Leicestershire
- Lincolnshire
- Merseyside
- Norfolk
- North Yorkshire
- Northamptonshire
- Northumberland
- Nottinghamshire
- Oxfordshire
- Rutland
- Shropshire
- Somerset
- South Yorkshire
- Staffordshire
- Suffolk
- Surrey
- Tyne and Wear
- Warwickshire
- West Midlands
- West Sussex
- West Yorkshire
- Wiltshire
- Worcestershire
Scotland
Glass-only replacement: get your guide price
Use the guide-price tool, or book a free survey for a written quote that fixes the price.