A-rated windows
A-rated windows and U-values
An A-rated window has an energy rating for its named frame and glass from one maker. In Ireland, NSAI's Window Energy Performance scheme rates it on heat loss (U-value), solar gain and air leakage. For the SEAI grant, the whole window needs a U-value of 1.4 W/m²K or lower (Irish Examiner).
- €7,110the median cost of new windows on a semi-D or end of terrace, January to June 2026 (SEAI)
- €500 to €900a standard uPVC window, installed (Expert Windows & Doors)
- 1 to 3 daysto fit most houses, after the windows are made (Expert Windows & Doors)
- 13.5% VATon windows supplied and fitted, not 23% (Revenue)
FreeNo obligationOne company rings you, not fiveNothing agreed until you accept a written price
The rating
What the rating measures
- Uw: heat lost through the whole window, frame and glass. Lower is better.
- Solar factor: how much of the sun's heat comes through, from 0 to 1.
- Air leakage: how tight it is. NSAI's scheme requires a Class 4 air tightness result first.
Each rating belongs to one window assembly from one manufacturer and doesn't transfer to another product (NSAI). Ask the fitter for the certificate for the window you're buying, not a brochure.
The numbers
The U-values that matter
| Figure | U-value, W/m²K |
|---|---|
| Median window on Irish BERs, homes built before 2011 | 2.71 |
| Single glazing (BER band) | 4.0 or more |
| Older double glazing (BER band) | 2.5 to under 4.0 |
| SEAI windows grant | 1.4 or lower |
| TGD L 2019 window backstop | 1.4 (down from 1.6) |
BER figures from the SEAI register, our sums (SEAI BER register). Grant: as the Irish Examiner reports SEAI's rule. Building regulations: SEAI's TGD L 2019 briefing.
On the quote
What to ask for in writing
- The whole-window U-value (Uw) for each window type, not the glass (Ug) alone.
- The frame system and the glass make-up: double or triple, gas fill, warm edge spacer.
- The energy rating certificate for that assembly.
- How it's fitted and sealed to the wall: a good window badly fitted still leaks air.
See it first
New windows on your own photo
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- We pass it to one company that covers your county.
- They ring you to measure up and price it in writing.
Preview of your photo, not a guarantee. Your photo goes to Google's Gemini service to make the picture and isn't kept.
A photo that works
- Daylight, from the footpath or the garden.
- The whole front of the house in the shot.
- Straight on, not at a sharp angle.
- No cars or bins in front of the windows, if you can help it.
Free quote
Get a price in 4 taps
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FAQ
Questions people ask
What does A-rated mean on windows?
An energy rating for one frame and glass assembly from one maker, based on heat loss, solar gain and air leakage (NSAI).
What U-value should new windows have?
1.4 W/m²K or lower to meet the SEAI grant (Irish Examiner); many new windows do better.
What U-value do my old windows have?
Your BER shows it. The median on Irish BERs for homes built before 2011 is 2.71 W/m²K (SEAI BER register).
Keep reading
Related guides
- Double vs triple glazingWhen triple glazing earns its place, and when it doesn't.
- Triple glazing costWhat the third pane adds a window and on a house.
- How to choose a window fitterThe survey, the written quote, the U-value and the guarantee.
- Grants and VATThe SEAI windows grant in brief, and 13.5% VAT.
Where these numbers come from (6 public sources, checked 3 November 2026)
- NSAI, Window Energy Performance (WEP) scheme
- Irish Examiner, all you need to know about aluclad windows, 18 Sep 2026
- SEAI BER Research Tool, public file (downloaded 29 October 2026, our sums)
- SEAI, TGD L 2019 Dwellings presentation (window backstop U-value)
- SEAI, Better Energy Homes: individual energy upgrades costs and grants, January to June 2026 (23,412 upgrades)
- Revenue, VAT on fixtures and fittings (reviewed Feb 2026)
Sources (1)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Expert Windows & Doors: expertwindows.ie