FENSA-registered glazing experts. Made-to-measure sealed units, shipped UK-wide, backed by a 10-year warranty.
A-rated energy-efficient sealed units — Building Regs compliant, EPC-uplift territory
A-rated under the British Fenestration Rating Council (BFRC) Window Energy Rating (WER) scheme means the whole-window assembly performs at or above the highest tier on the A++ to E scale. For glass-only retrofit, that translates to a centre-pane U-value of around 1.2 W/m²K or better, achieved with a soft-coat low-E inner pane, argon-filled cavity, and warm-edge spacer. Specify A-rated for Approved Document L compliance, for an evidenced EPC-rating uplift on resale, and for the lowest heat-bill running cost — typically 50-60% less heat loss than 1990s uncoated double glazing. Every unit in this collection is built to A-rated centre-pane spec; whole-window WER ratings depend on frame and installation.
Upgrading for warmth, bills, and resale value
If you're aiming to move the EPC needle (typically D → C, sometimes C → B), A-rated glazing is one of the cheaper interventions per kWh saved. We supply the units; pair with a competent fitter and the WER certificate covers the whole-window rating. Free spec advice on the helpline, 10-year edge-seal warranty, FENSA installer recommendations in your postcode.
Configure my A-rated unitInstaller, developer, retrofit specialist
BFRC and CE/UKCA documentation shipped on request — useful for Part L sign-off, EPC assessments, and PAS 2035 retrofit jobs. Net 30 trade accounts, tiered discount on 5+/20+/50+ unit orders. Bespoke quotes for ECO4-funded jobs and large-developer schemes. WER A and A+ ratings available depending on glass-frame combination.
Trade pricing & bulk ordersWhich A-rated spec do you need?
Five standard A-rated builds, plus an A+ upgrade option. Pick the closest match — performance and price step up across the range.
Standard A (24mm)
4mm soft-coat low-E + 16mm argon + 4mm clear, warm-edge spacer. U=1.2 W/m²K. The default A-rated retrofit unit.
Enhanced A (28mm)
4mm soft-coat low-E + 20mm argon + 4mm clear. U=1.1 W/m²K — marginal gain over 24mm, worth specifying where rebate allows.
A+ rated
Dual low-E coating, warm-edge spacer, argon fill. U=1.0 W/m²K on a 28mm DG build. Whole-window WER A+ achievable on good frames.
A-rated + toughened
A-rated build with one or both panes toughened to BS EN 12150. For doors and low-level critical-location glazing.
A-rated + acoustic
6.4mm laminated acoustic outer + 16mm argon + 4mm low-E inner. U=1.2 W/m²K, Rw 38-40 dB. Thermal + acoustic in one unit.
Custom low-E build
See the low-E coated glass collection for individual coating options and the configurator for fully custom A-rated specs.
What "A-rated" actually means under WER and BFRC
A short explainer so you can specify with confidence — and so you know what paperwork to ask for at delivery.
The 5-point A-rating brief
- WER is a whole-window rating — A++ down to E. It combines U-value (heat loss), solar factor g (free passive solar gain), and air leakage L into a single number. Glass-only retrofit doesn't certify a WER rating, but the underlying U-value puts the assembly into A-rated territory.
- BFRC is the UK certification body for WER. CE/UKCA covers BS EN 1279 (sealed-unit performance and durability); WER sits on top.
- The Part L route: Approved Document L (England 2026) requires a whole-window U-value of 1.4 W/m²K or better on replacement. An A-rated centre-pane unit clears that with margin, even after frame factor.
- The EPC route: SAP-2012 and SAP-10 both credit A-rated glazing against the heat-loss element of the EPC calculation. Typical bump: D → C or C → B over a whole-house replacement.
- Documentation: on request we ship a Declaration of Performance (BS EN 1279-5), a CE/UKCA mark, and a glass coating data sheet (emissivity, light transmittance, solar factor, U-value). Useful for Part L sign-off, EPC assessor inspections, and PAS 2035 retrofit jobs.
Pricing & what's in the box
Prices on this collection are "From £X" at the smallest stock size with the standard A-rated build (4-16-4 argon + soft-coat low-E + warm-edge spacer). Custom sizes, A+ dual-coat upgrades, toughened or laminated safety, acoustic interlayers — all priced live in the configurator.
A-rated glazing — common questions answered
Q: A vs B vs C rating — what's the difference in practice?
WER bands are calibrated so that A-rated and above is net energy positive over a heating season (the solar gain through the unit outweighs the heat loss), B-rated is roughly neutral, and C-rated is net negative. C-rated was the old "good" standard 10-15 years ago; A is now the residential default. In raw U-value: A is around 1.2 W/m²K or better, B is around 1.4, C is around 1.6. The price gap between A and C on a typical stock-size DG unit is single-digit percent — almost always worth specifying A.
Q: What's the difference between BFRC, CE, and UKCA marks?
BFRC certifies the WER (whole-window energy rating) — A++ to E. CE / UKCA certifies that the sealed unit meets BS EN 1279 (durability, gas retention, weathered tests). Every unit Pane Relief ships carries CE/UKCA. BFRC ratings are issued by the window manufacturer for a full window assembly, not for the glass alone — but the underlying glass spec sets the ceiling.
Q: How much EPC bump can I expect from a whole-house A-rated swap?
Typical outcomes from RdSAP assessments: a 1970s-1990s semi-detached home with original uncoated DG (U around 2.7-3.0) upgrading to A-rated low-E argon (U around 1.2) gains 4-8 SAP points — enough to move D to C in most cases, and C to B in some. The exact number depends on the proportion of wall area that's glazed and the rest of the fabric. Combine with loft and cavity-wall insulation for a bigger jump.
Q: Does A-rated cost a lot more than basic double glazing?
No — the cost delta is small. The expensive part of a sealed unit is the glass itself, not the coating. A 4-16-4 plain DG unit and a 4-16-4 soft-coat low-E argon A-rated unit differ in retail price by typically 8-15% — and the A-rated unit pays that back in heating-bill savings inside 4-7 years. There's no rational reason to specify non-A unless you're matching a heritage or planning constraint.
Q: Will A-rated overheat a south-facing room in summer?
Standard A-rated low-E is tuned to let in solar gain (the whole point of the WER A rating — it's heat balance, not just heat loss). On large south or west-facing openings, lantern roofs, or conservatory roofs, that can cause summer overheating. The fix is a solar-control low-E (Pilkington Suncool, Saint-Gobain Cool-Lite) — same U-value but with the g-value reduced to 0.3-0.4. Trade-off is a slightly cooler-toned reflection and a marginal hit to WER score. See the low-E coated glass collection for solar-control variants.
Q: Is A-rated worth it on north-facing windows where there's no solar gain?
Yes — possibly more so. The "energy-positive" calculation in WER assumes a UK-typical orientation mix. On a north-facing window there's negligible solar gain at any time of year, so the rating reflects pure heat-loss reduction. A 30-40% lower U-value than uncoated DG on a north elevation means proportionally lower heat loss — about £15-£30/year per medium-sized window at 2026 gas prices.
Q: What's the difference between A and A+ and A++?
A is the baseline pass (typically U around 1.2 W/m²K). A+ is achieved with dual low-E coating or krypton fill (U around 1.0). A++ requires triple glazing — and is essentially the entry to the Passive House territory. For most UK retrofits, A is plenty; A+ is worth it on south-facing rooms or on big openings; A++ is for new-builds aiming at the highest energy standards.
Q: Will an A-rated unit also reduce condensation?
Yes — significantly. Internal condensation forms when the room-side glass surface drops below the dew point of the room air. An A-rated unit's inner pane runs 4-6°C warmer than a 1990s uncoated DG inner pane (because the cavity holds heat better). That's usually enough to eliminate the morning mist that forms on cold winter days. See the condensation fix guide for more detail.
Q: Do I need to notify Building Control for an A-rated retrofit?
For glass-only replacement of an existing window (sealed unit only, frame stays), no Building Control notification is required — it's a like-for-like maintenance job. For a whole-window replacement, you do need to notify under Approved Document L; if your installer is FENSA-registered they'll self-certify on your behalf. Always specify A-rated for replacement to clear Part L automatically.
Q: What's the lead time?
Stock-size A-rated units: 5-7 working days. Custom rectangular: 7-10 working days. A+ rated dual-coat or krypton-filled: 10-14 working days. Toughened or laminated A-rated builds: add 2-3 working days. Emergency same-day boarding available for broken glass — call the helpline.
Related guides and specifications
Need help choosing the right A-rated spec?
Call the helpline on 0117 330 3057 (08:00-18:00 Mon-Fri), or request a quote. Trade accounts unlock live tier pricing and Net 30 terms.