Replacement glass units for every window style, made to your measurements and delivered across the UK
FENSA Registered BS EN 1279 10-Year Warranty
Trade pricing & bulk orders
Replacement window glass — sealed units made to your sizes
Misted between the panes? Cracked? Failing to keep the heat in? In most cases you don't need a whole new window — just a new sealed unit. Pane Relief supplies replacement double-glazed, triple-glazed, low-E (A-rated), acoustic, toughened, laminated, obscure, and Georgian-bar sealed units to fit casement, sash, bay, tilt-and-turn, fixed-light, and conservation windows. Pick the window type below to see real prices and lead times — or use the configurator if your spec or size is non-standard.
Replacing your own window glass
Free delivery to Bristol (BS) postcodes; £150 + VAT (£180) anywhere else on the UK mainland. 10-year manufacturer warranty on edge-seal integrity. FENSA-registered fitter recommendations in your postcode. Phone helpline (9am–5pm, Mon–Fri) for sanity-checking your measurements before you order. Most stock-size units ship in 5-7 working days.
Configure my unitInstaller, builder, glazier
Trade accounts, tiered volume discount on 5+/20+/50+ unit orders, scheduled site delivery, priority dispatch for FENSA installers and developers. Every unit ships UKCA-marked with BS EN 1279 compliance; Declaration of Performance on request. Bespoke quotes via the trade portal.
Trade pricing & bulk ordersWhich window type are you replacing?
Six common window scenarios. Pick the closest match — each links to the relevant flagship product or filtered range.
Standard casement
UPVC, timber, or aluminium casements. Most common UK type — 24mm or 28mm rectangular sealed units.
Bay window
3-pane, 4-pane, or 5-pane bay configurations. Angled or square. We supply matching units across all lights.
Sash window
Vertical sliding sash. Slim 14mm Histoglass-equivalent for conservation areas. Listed-building friendly options.
Tilt & turn
Continental-style inward-opening. Often larger panes — toughened recommended on units over 1m².
Bedroom window
Acoustic and thermal options. Laminated acoustic interlayer cuts road and aircraft noise by up to 44 dB Rw.
Bathroom (obscure)
Privacy-rated obscure glass — Levels 1-5 (Pilkington Texture range). Toughened required for shower-screen height.
Measure twice, order once
For windows the measure is the same as for doors: measure the rebate, not the frame opening. We need the sealed-unit size, not the daylight opening.
The 5-step measure
- Open the window or carefully remove a glazing bead. Measure visible glass width at top, middle, and bottom — use the smallest number.
- Measure visible glass height at left, middle, and right — use the smallest number.
- Then add 25mm to the width and 25mm to the height.
- Measure the overall sealed-unit thickness with vernier callipers (typical: 24mm, 28mm, or 36mm).
- Photograph the frame profile, the rebate depth, and any kitemark stamp on the existing glass. Send to our team for a free spec-match if you're unsure.
Pricing transparency
Prices include VAT. The "from" price on each product page is for the smallest stock size at base specification (4mm-20mm-4mm argon-filled annealed). Custom sizes, toughened or laminated safety, low-E coatings (Planitherm, Optitherm), acoustic interlayers (PVB acoustic), obscure patterns, Georgian bars, or oversized panels are all priced live in the configurator.
Window glass — common questions answered
Q: My window is misted between the panes. Do I need a whole new window?
No — almost never. Misting between the panes means the edge-seal on the sealed unit has failed and moisture has migrated into the air gap. The frame, hinges, locks, and gaskets are usually fine. You just need a new sealed unit fitted into the existing frame. That's typically 60-80% cheaper than a full window replacement. If the frame itself is rotten, twisted, or has failed locks then yes — replace the whole window. Send a photo on the helpline for a free diagnosis.
Q: What's the difference between a sash window measure and a casement measure?
Both are measured at the rebate, but on sash windows the glass typically sits in putty (timber sashes) or a slim bead (modern UPVC sashes) rather than a deep gasketed rebate. The rule of thumb: ease back the putty fillet or pop a bead, measure visible glass plus 3mm of overlap each side. Listed sashes often require slim-profile units (14mm overall, Krypton-filled) to retain the timber muntin proportions — those are a separate stock line; ask via the helpline.
Q: Is low-E worth paying for?
Yes — for any window receiving long daylight hours. A low-E soft-coat unit (Planitherm Total+, Optitherm S3) drops the U-value from around 2.8 W/m²K (standard double-glazed) to 1.2-1.4 W/m²K. On a typical 3-bed UK semi that's a quantifiable drop in heating bills (typically £80-£140/year per window, depending on orientation). All our stock units use a low-E coating by default unless you opt out; the price difference is small and the payback is fast.
Q: U-value vs g-value — what do they mean and which matters more?
U-value (W/m²K) measures heat loss out — lower is better. g-value (also called solar factor) measures solar heat gain in — higher is better in winter but worse in summer. For most UK homes a unit with low U-value (~1.2) and mid g-value (~0.5) is the right balance. South-facing rooms that overheat in summer can benefit from a solar-control coating (lower g-value, around 0.3) — but those rooms are rare in the UK climate, so don't over-spec by default.
Q: A-rated vs C-rated — what's the difference?
BFRC (British Fenestration Rating Council) ratings A++ to E represent the net energy efficiency of a complete window assembly — frame plus glass. Sealed units alone don't get a BFRC rating; the assembly does. For a fair like-for-like, our stock low-E units typically push the existing frame from C-rated to A or A+ once retrofitted. If you're targeting a specific rating for a planning condition or new-build SAP submission, tell us the target — we'll spec the right glass build-up.
Q: I get condensation on the inside of the window. Is the glass failing?
Almost never — internal condensation is a humidity and ventilation problem, not a glass problem. It happens when warm moist indoor air contacts a cold internal glass surface. Fix: more trickle-vent airflow, run extractor fans during cooking and showering, dry laundry outside. Upgrading to a low-E unit raises the internal glass surface temperature and reduces (but doesn't eliminate) condensation. Misting between the panes (inside the sealed unit, where you can't wipe it off) is a different problem — that's a failed edge-seal and the unit needs replacing.
Q: I'm in a Conservation Area / listed building — what are my options?
Conservation and listed properties typically require slim-profile units (10mm-14mm overall thickness) to retain the original timber muntin proportions and external sightlines. We stock Krypton-filled slim units (Histoglass-equivalent) that hit U-values around 1.6 W/m²K — a meaningful upgrade on single glazing while satisfying most planning officers. Confirm with your local conservation officer first; we'll supply a spec-sheet for their approval before you order.
Q: Is safety glass required for window glass?
Sometimes. Approved Document N and BS 6262-4 mandate impact-resistant glazing (toughened BS EN 12150 or laminated BS EN 14449) in any pane that sits below 800mm from floor level, or near a door. Bathroom windows, low-cill bedroom windows, and floor-to-ceiling glazing all typically require safety glass. The configurator highlights critical-location panels automatically once you enter the dimensions and cill height.
Q: Acoustic glass — does it really work?
Yes, for the right frequencies. A standard double-glazed unit gets you to about 28-30 dB Rw acoustic insulation. A laminated acoustic unit (with PVB acoustic interlayer) jumps to 38-44 dB Rw — a noticeable, measurable improvement on busy roads, near flightpaths, or in railway corridors. If you're not sure whether acoustic glass is worth the upgrade for your situation, read the acoustic glass guide — it shows the dB drops by traffic type.
Q: What's the warranty and lead time?
10-year manufacturer warranty on edge-seal integrity (BS EN 1279-2 weathered durability), 10-year on coatings. Stock-size units: 5-7 working days. Custom rectangular double glazing: 5–7 working days. Shaped, arched, or oversized (any dimension >1500mm): 10-14 working days. Toughened or laminated specs: 10–14 working days. Mis-measured units are remade at the same price again.
Related guides and specifications
Need help choosing the right window glass?
Call the helpline on 0117 330 3057 (9am–5pm, Mon–Fri), or request a quote. Trade accounts unlock live tier pricing.