Are your windows A-rated as standard?

Yes — the standard 28mm argon-filled low-E unit with warm-edge spacers achieves an A rating in the Eurologik system, with no upgrades needed.

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.

Is A++ worth chasing?

A++ generally needs triple glazing. If you want the warmest possible glass — cold-facing bedrooms, exposed plots — choose triple in the designer; otherwise A-rated double is the value sweet spot.

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.

Window energy ratings and U-values

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 windows are A-rated as standard with 28mm argon-filled double glazing, and the Eurologik system achieves U-values as low as 0.8 with its highest-spec glazing.

Design an A-rated window

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.

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.

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 — the standard 28mm argon-filled low-E unit with warm-edge spacers achieves an A rating in the Eurologik system, with no upgrades needed.
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.
Is A++ worth chasing?: A++ generally needs triple glazing. If you want the warmest possible glass — cold-facing bedrooms, exposed plots — choose triple in the designer; otherwise A-rated double is the value sweet spot.
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.