Double glazing U-value
Double glazing with us is insulating glass with a coating and a gas-filled cavity, standard in every new window, with a Ug of 1.1 W/m²K. We don't supply double glazed units on their own for an existing frame.
Double glazing and A-rated windows
What counts in England is the whole window: Approved Document L asks a replacement window for a U-value of 1.4 W/m²K or a WER band B. The Ug of the glass is one part of that; the U-value of the whole window is in your quote.
U-value of our double glazing
The U-value of double glazing on its own is its Ug: ours is 1.1 W/m²K, and the lower the figure, the better it insulates. Triple glazing is at 0.6. The U-value of the whole window, which Building Regulations look at, also depends on the frame; it is in your quote.
Drawbacks of double glazing
Compared with triple glazing it insulates less. In its favour: it is lighter and thinner, so it fits more profiles and larger sashes.
Double glazing in existing frames
We don't supply that: with us, glass only comes in a new window. If you only want new glass in a sound frame, that's a job for a glazier.
How thick is double glazing?
That depends on the build-up: two panes with a cavity between them. Which glass fits a profile is on the profile page; the Schüco LivIng, for example, takes units of 24 to 52 mm.
How to recognise double glazing
The spacer bar between the panes often carries the maker or type of the glass, and the invoice or glass report gives the Ug. If in doubt, ask a glazier.
Frequently asked questions
What is double glazing?
Two panes of glass with a sealed cavity between them, usually with a coating on one pane and a gas fill. It keeps warmth in far better than a single pane.
What is A-rated double glazing?
A rating of the whole window, frame and glass together, under the Window Energy Rating. The U-value or rating of your window is in our quote.
How thick is double glazing?
That differs per build-up. Which glass fits a profile is shown on each profile page.
Can you put new double glazing in old frames?
Not through us: we only supply glass in a new window. For new glass in an existing frame, go to a glazier.
How do I recognise my double glazing?
Look at the spacer bar between the panes, or at the invoice or glass report, where the Ug is given.
Do I need Building Regulations approval for double glazing?
Replacing windows is notifiable work in England and Wales: an installer registered with FENSA or Certass notifies it, or you notify building control beforehand. We supply, we don't install.
Know what you want? Put it together.
No form first: you watch your window take shape as you choose. The price follows in the quote, within three working days.
Configure your window or door
Where we have a guide price, it is on the page, not behind a form — not a quote and not a final price; the amount for your sizes is in the made-to-measure quote.
Request a quote