FENSA-registered glazing experts. Made-to-measure sealed units, shipped UK-wide, backed by a 10-year warranty.
32mm triple glazing — best balance of thermal vs frame compatibility for retrofit
If your frame rebate can accept 32mm overall but won't take 36mm, the 32mm TG build is the sweet spot for retrofit triple glazing. The 32mm build (typically 4mm-10mm-4mm-10mm-4mm with argon fill and two low-E coatings) gives you wider cavity spaces than 28mm TG — and that 2mm of extra cavity per gap translates into meaningfully better thermal performance: a U-value around 0.9-1.0 W/m²K versus around 1.0-1.1 for 28mm TG. It's also lighter on the hardware than 36mm TG (the 4mm panes throughout keep weight down), so it works on hardware that would struggle with the full 36mm spec. Right call for mid-2010s retrofits where the frames were specified DG-or-TG-tolerant, and for the eco-conscious refurb that wants thermal performance without a frame replacement.
The retrofit TG sweet spot
Frames built 2010-2020 commonly accept up to 32mm sealed-unit thickness — a deliberate over-sizing by manufacturers to allow future TG retrofit. If yours fits that band (check the rebate depth: 26mm or more), 32mm TG gives you better thermal than 28mm without the hardware penalty of 36mm. Free rebate-depth check via the helpline if you're not sure what your frame can take.
Configure 32mm TGRetrofit specialist, architect, glazier
UKCA-marked with BS EN 1279 compliance and Declaration of Performance on request. Specify 32mm TG when client briefs call for "best practical TG for existing frames" — the 2mm extra cavity over 28mm TG translates into measurable U-value drop without the hardware overhaul that 36mm needs. Trade tier pricing on 5+/20+/50+ unit orders, scheduled site delivery.
Trade pricing & bulk ordersFrame and project scenarios for 32mm TG
Six common situations where the 32mm build hits the right balance of thermal and compatibility.
Frame only takes 28mm — use 28mm TG
Pre-2010 UPVC or slim-aluminium frames typically cap at 28mm. See the 28mm TG range for those.
2010-2020 UPVC retrofit
TG-tolerant UPVC frames from this era. Pop a bead, measure the rebate — 26mm depth is the threshold.
Quality timber casement
Engineered timber sashes designed for either DG or TG. 32mm hits the thermal sweet spot.
Eco-refurb / EnerPHit retrofit
EnerPHit-tier retrofit work where U-values under 1.0 W/m²K are needed but frame swap is out of scope.
Large picture / fixed lights
Fixed (non-opening) large lights where hardware load isn't a constraint and thermal performance matters most.
Custom 32mm TG
Shaped, oversized, or non-standard rectangles in 32mm spec. Configure live.
Verify the rebate depth — the one critical check
32mm TG only works in frames designed to take it. The single most important pre-order check is the rebate depth.
3-point pre-order check
- Rebate depth. 32mm TG needs a 26mm minimum rebate depth — pop a glazing bead and measure with a steel rule. Sub-26mm means you need 28mm TG (22mm rebate) or DG instead. Over 26mm is fine — modern TG-tolerant frames typically have 30-34mm rebate.
- Hardware load check. 32mm TG weighs roughly 30 kg/m² (versus 27 for 28mm TG and 17 for DG). Standard friction stays cope up to about 25 kg total load — over 1m² you may need heavy-duty hinges or a hardware swap.
- Sealed-unit dimensions. Same rule as DG and 28mm TG — measure rebate-to-rebate visible glass at top/middle/bottom, take the smallest, add 6mm for the 3mm-each-side overlap.
Pricing transparency
32mm TG sits at a small premium over 28mm TG (typically 5-12% more per square metre — the wider cavity uses more argon and adds production handling). Versus low-E DG it's 45-60% more expensive per square metre. Payback on energy savings: 6-9 years on south or west exposed walls, 10-13 years on north or sheltered. Trade-tier pricing on volume.
32mm triple glazing — common questions answered
Q: Why pick 32mm TG over 28mm TG?
Two extra millimetres of cavity per gap (10mm gaps versus 8mm) makes a measurable thermal difference. 32mm TG sits at around 0.9-1.0 W/m²K; 28mm TG at around 1.0-1.1 W/m²K. That's a roughly 10% U-value improvement — meaningful over the lifetime of the unit, particularly on exposed elevations. If your rebate can take 32mm, take it. If it can only take 28mm, the smaller build still gives you most of the TG benefit.
Q: Why not just go straight to 36mm TG?
Three reasons. (1) Most UK residential frames pre-2020 won't take 36mm — the rebate is too shallow. (2) 36mm TG often uses 4mm-6mm-4mm-6mm-6mm or similar asymmetric builds with thicker outer panes, pushing weight up to around 35-38 kg/m² — too heavy for many existing hinges and friction stays. (3) The thermal gain from 36mm over 32mm is small (around 0.05 W/m²K) versus the compatibility and hardware cost. 32mm TG is the right call when you want TG benefits inside a retrofit envelope; 36mm is for new-build or full-frame-swap work.
Q: How heavy is 32mm TG versus my existing DG?
Roughly 75% heavier than equivalent DG (30 kg/m² versus 17). For most casement lights under 1m², standard hardware copes. For lights over 1m² — tilt-and-turn lower lights, French casement leaves, large picture-window opening sashes — you'll likely need to inspect or upgrade the hinges. Fixed (non-opening) lights have no hardware constraint and accept TG up to oversized dimensions without issue.
Q: Argon or krypton fill in 32mm TG?
Argon by default — the 10mm cavities are in the argon "sweet spot" (8-14mm gap is where argon delivers maximum efficiency) so argon is the cost-effective and thermally optimal choice. Krypton fill is available on request but the marginal U-value improvement (0.03-0.05 W/m²K) is small and the krypton premium is large — krypton-fill 32mm TG is rarely specified outside EnerPHit or Passive House retrofit work.
Q: Can 32mm TG be specified in safety glass?
Yes — toughened (BS EN 12150) on the inner and/or outer pane, or laminated (BS EN 14449) on the inner pane. Critical-location safety-glass requirements apply: panes below 800mm AFFL, within 300mm of a door edge, or in floor-to-ceiling primary glazing must be safety-rated. The configurator flags critical-location warnings automatically once you enter dimensions and cill height.
Q: How is 32mm TG marked — UKCA, BS EN, kitemark?
Every 32mm TG unit ships UKCA-marked per the 2022 UK construction-product requirements. Compliance includes BS EN 1279 (sealed-unit weathered durability and gas-fill retention), BS EN 410 (light and solar characteristics), and where safety glass is included BS EN 12150 (toughened) or BS EN 14449 (laminated). Declaration of Performance documents available on request — useful for SAP submissions, planning conditions, EnerPHit certification, and BFRC rating evidence.
Q: How does the 32mm build affect daylight transmittance?
Three panes plus two low-E coatings means visible daylight transmittance drops to around 67-70% (versus 76-80% on coated DG and 80-82% on uncoated clear DG). On most habitable rooms that's not noticeable in practice — the human eye is far more sensitive to colour cast (low-E coatings can read as a faint green-blue) than to absolute transmittance. North-facing rooms with daylight-priority briefs may want to stick with low-E DG or even uncoated clear; for everything else the 32mm TG is a sound thermal-versus-daylight trade.
Q: Lead time and warranty?
10-year manufacturer warranty on edge-seal integrity (BS EN 1279-2 weathered durability) and 5-year on low-E coatings. Lead time: 7-10 working days for rectangular stock-spec, 10-14 days for shaped or oversized (any dimension over 1500mm), 12-16 days for shaped TG with safety-glass variants. Free UK mainland delivery on all orders.
Related guides and specifications
Frame takes 32mm? You're in the TG sweet spot.
Call the helpline on 0117 330 3057 (08:00-18:00 Mon-Fri), or request a quote. Free rebate-depth check and hardware-load advice.