FENSA-registered glazing experts. Made-to-measure sealed units, shipped UK-wide, backed by a 10-year warranty.
Triple-glazed windows — Scandinavian-spec sealed units, U ≤ 0.8 across the casement
Replacement triple-glazed window units engineered to Scandinavian thermal spec — 44mm or 52mm sealed units, two soft-coat low-E surfaces, argon or krypton gas fill, warm-edge spacer, U-value down to 0.6 W/m²K centre-pane. This collection covers TG windows specifically — not doors, not roof units. If you're retrofitting a passive-house standard window programme, hitting Future Homes Standard U-values, or simply tired of paying to heat the air outside, TG is the spec that gets you there. Pane Relief manufactures stock TG sizes from 600×600mm up to 2400×1500mm in standard production, with oversized panels to 3200×1800mm on enquiry.
Refurb or passive-house retrofit
If you're insulating a property to Passive House EnerPHit or Future Homes Standard, TG windows are non-negotiable. We supply the sealed units to fit your new frames (TG requires deeper rebates than DG — typically 32mm-52mm) or to retrofit into existing TG-spec frames. Free UK mainland delivery, 10-14 working days on stock TG spec, 10-year edge-seal warranty same as DG.
Configure my unitPassive-house installer, eco-builder
For Passive House Institute (PHI) certified projects, AECB / Passivhaus Trust schemes, or Future Homes Standard new-builds — we supply the TG sealed units to your spec with full BS EN 1279 documentation, U-value test data, and (on enquiry) Passive House Institute (PHI) component certification evidence. Net 30 trade accounts, tier discount on 5+/20+/50+ batches.
Trade pricing & bulk ordersSix TG window applications
Pick the closest match — each tile links to the relevant flagship or filtered slice. Note: this collection is window-specific. For doors see door-glass-units; for roof / commercial see those collections.
UPVC casement TG
44mm 4-12-4-12-4 argon TG for modern UPVC casement profiles. U-value 0.7-0.8 W/m²K.
Timber sash & casement
Slim 32mm or 36mm TG for heritage timber frames where rebate depth is constrained.
Aluminium fixed light
52mm 4-16-4-16-4 krypton TG for high-performance aluminium curtain wall residential or premium spec.
Tilt & turn
European-spec tilt-and-turn requires TG for weight-loaded hinge spec. We supply matching unit thickness.
Passive House (EnerPHit)
52mm krypton TG with U ≤ 0.65 W/m²K. PHI-component evidence on request.
Bespoke TG window size
Any rectangular TG size between 600×600 and 3200×1800mm — configurator gives live pricing.
TG window spec — what you're actually paying for
Triple glazing is more than "an extra pane". Here's what determines real-world performance.
The five performance variables
- Pane build — 4-4-4mm standard; outer 6mm or 6.4mm laminated steps up acoustic performance.
- Spacer thickness — 12mm spacer = 44mm total (standard); 16mm spacer = 52mm total (best thermal); <10mm wastes the TG benefit.
- Gas fill — argon (cheap, 90% of installs) drops U-value vs air by ~0.4 W/m²K; krypton (premium, ×5 cost) drops a further ~0.1-0.15 W/m²K.
- Low-E coatings — Two soft-coat surfaces (surfaces 2 and 5) reflect long-wave infrared back into the room. Without low-E, TG underperforms a quality low-E DG.
- Edge spacer — Warm-edge polymer spacers (Swisspacer, Edgetech Super Spacer) outperform aluminium by 0.1-0.2 W/m²K on whole-window U-value.
Pricing transparency
TG carries roughly a 40-70% price premium over equivalent DG, depending on spec. The configurator surfaces exact cost as you toggle pane builds, spacers, gas fills, and coatings — live pricing, no waiting for a quote.
For Passive House projects we also quote with PHI-component evidence (Uw ≤ 0.8 W/m²K verified for the unit + frame assembly). Tier discount on 5+/20+/50+ batches applies.
Triple-glazed windows — common questions
Q: Will my existing window frames take a TG sealed unit?
Probably not. TG sealed units are 44mm or 52mm thick; most existing UK windows are framed for 24mm or 28mm DG. Swapping is rarely a simple glass swap — the frame rebate is too shallow. If your window programme is set for a full frame replacement (as part of a refurb), TG slot-in is straightforward; if you're trying to retrofit TG into existing DG frames, you'll typically need new frames or a slim 32mm TG variant. Send a frame photo + cross-section measurement and we'll advise.
Q: What U-value should I be targeting?
Building Regs Part L 2026 requires whole-window U-value ≤ 1.4 W/m²K for replacement windows — well inside DG spec, so TG isn't required. Future Homes Standard (new-build from 2026) tightens to ~1.2 W/m²K — still achievable on premium DG. Passive House EnerPHit retrofit targets ≤ 0.85 W/m²K — TG required. Passive House new-build targets ≤ 0.8 W/m²K — TG with krypton typically required.
Q: Argon or krypton — when's krypton worth the extra cost?
Argon-fill 12mm-spacer TG hits about 0.7 W/m²K centre-pane; krypton-fill 12mm hits about 0.5-0.6 W/m²K. For most homeowner refurbs and Future Homes Standard new-builds, argon is the right call (roughly ×5 cheaper, >90% of the thermal benefit). For Passive House certification or where the spacer is constrained to 8-10mm (slim TG in heritage frames), krypton's higher density makes the difference and is worth the premium.
Q: Is TG always better than DG?
Not always. A quality DG unit (4-20-4 argon, two-surface low-E, warm-edge spacer) achieves around 1.1 W/m²K — comfortably inside Building Regs and well-priced. TG adds significant weight (a 1m×1m TG unit is ~25-30kg vs ~16-18kg for DG) which loads hinges and may require frame upgrades. TG is materially better for Passive House, north-facing exposure, very large panels, or noise reduction — but for an average south-facing UPVC casement, quality DG is the cost-effective sweet spot.
Q: Does TG help with noise / acoustic performance?
Standard 44mm TG hits about Rw 35-37dB — modestly better than 24mm DG (Rw 31-33dB). The bigger acoustic gain comes from stepping the outer pane to 6.4mm or 6.8mm laminated acoustic glass (Pilkington Optiphon, Saint-Gobain Stadip Silence), which lifts Rw to 39-41dB on a TG sandwich. For very heavy noise (flightpath, motorway), acoustic-laminated TG is the spec — see also the acoustic glass guide.
Q: Does TG cause overheating in summer?
It can — TG holds heat in (which is the point) and on south- or west-facing exposure that can drive uncomfortable summer overheating. The fix is solar-control low-E on surface 2 (g-value 0.30-0.40), which lets winter sun in but rejects most summer solar gain. For Passive House projects we'd typically pair TG with solar-control low-E and external shading — overheating risk-assessment is part of the PHPP modelling.
Q: What's the lead time on TG window units?
Stock-spec TG (44mm or 52mm, argon, soft-coat low-E): 10-14 working days. Krypton-fill or PHI-component certified spec: 14-21 working days. Slim 32mm-36mm TG for heritage frames: 14-21 working days (slim-line spacers are a specialist supply). Oversized TG: 14-21 working days, longer for jumbo plate.
Q: Will TG help with condensation?
Yes — significantly. Internal-pane condensation forms when the inner glass surface drops below the dew point of the room air. TG keeps the inner pane warmer than DG (because the middle pane buffers heat loss to the cold outer pane), so the dew point is rarely reached. For severe condensation issues, TG combined with warm-edge spacer and ventilation improvements is the textbook fix. See also the energy-rated units guide.
Q: Do you supply PHI-certified Passive House components?
The sealed unit alone isn't PHI-certified — only the full window assembly (frame + glass + spacer + installation) earns PHI certification. We supply the sealed unit to your PHI-certified frame manufacturer's spec, with the U-value, g-value, and Psi-value evidence required to support the overall PHI submission. Send the certification target and frame spec and we'll match the glass build.
Related ranges and guides
Hitting Passive House or Future Homes Standard?
Configure your TG window unit in 60 seconds, or send the PHPP target for a spec match. Helpline 0117 330 3057.