Window energy ratings explained: what A rated, WER and U-value mean
A window's energy performance is described two ways: a Window Energy Rating (WER), the A++ to E coloured label, like a fridge, and a U-value, the engineering measure of heat loss in W/m²K where lower is better. Our standard windows, with 28mm argon-filled double glazing, are A rated under BFRC licence 3220. We supply only: you measure and order, we make and deliver, and you or your fitter install.
WER vs U-value: what each measures
The WER is a whole-window balance sheet: it combines heat lost through the frame and glass, air leakage, and free solar heat gained through the glazing, into a single annual figure banded A++ to E. A U-value measures only loss: the rate heat escapes per square metre for a given temperature difference. A window can score a good WER partly through solar gain, which is why both numbers are quoted.
Our rating: BFRC licence 3220
Inbray Ltd, the company behind New uPVC Windows, holds British Fenestration Rating Council (BFRC) licence 3220 for the Eurologik 70 Casement, rated A. That is the rating of the standard 28mm double glazed windows we sell.
You don't have to take our word for it: enter licence number 3220 in the BFRC consumer search. Our other standards and certificates are listed on our products page.
What Building Regulations require
For replacement windows in England, Approved Document L requires new windows to achieve a U-value of 1.4 W/m²K or better, or WER band B or better. Our standard A-rated specification clears both routes, so a compliant order is simply our default. You don't need to option anything up for regulations.
- A++
- A+
- A← Our standard
- B← Building Regs minimum
- C
- D
- E
Where the performance comes from
- Six-chambered Eurologik 70mm frames: each chamber is a still-air insulating break
- 28mm double glazed units: 4mm low-E glass, 20mm argon-filled cavity, warm-edge spacer
- Low-emissivity coating reflects room heat back inside while admitting solar gain
- Twin-leg gaskets and internal beading for airtightness, tested to BS 6375
- Optional 36mm triple glazing where you want the lowest U-values
What an upgrade is worth
Replacing single glazing or early sealed units with A-rated windows is the big step. That's where the comfort and heating-bill change is felt. Moving from A-rated double to triple is a smaller increment: worthwhile for cold-facing bedrooms and exposed sites, rarely transformative elsewhere. Our double vs triple guide gives the honest comparison.
Frequently asked questions
- Are your windows A-rated as standard?
- Yes. With the standard 28mm argon-filled low-E unit and warm-edge spacers, our Eurologik windows are A rated, with no upgrades needed. That's BFRC licence 3220, which you can check on the BFRC consumer search.
- What U-value do Building Regulations require?
- For replacement windows in England: 1.4 W/m²K or better, or WER band B or better. Our standard specification satisfies both.
- Does triple glazing give a higher rating?
- Triple glazing lowers the heat lost through the glass, so it gives a lower U-value. The licensed rating we can quote is A, for our standard double glazing (BFRC licence 3220); we don't quote a higher rating for triple glazing. If you want the warmest glass (cold-facing bedrooms, exposed plots), choose triple in the designer; otherwise A rated double glazing is the value choice.
- Does frame colour affect the rating?
- No, foiled colours change the appearance of the profile, not its thermal structure. The chambers and glazing do the insulating.
- Do trickle vents ruin the energy rating?
- No, vents are part of the tested specification and are closable. They exist to meet ventilation rules (Part F), which work alongside the thermal rules (Part L), not against them.
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