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Passive House triple glazing — PHI-certified component spec for new-build and EnerPHit retrofit
Passivhaus Institut (PHI) certification demands a glazing centre-pane U-value of 0.80 W/m²K or better, with a solar factor (g-value) of around 0.50 to ensure the unit is "energy-positive" on the standardised PHPP heat-balance calculation. That's a different specification ladder from BFRC A-rated: dual low-E coatings on the inner faces of a 36mm-44mm triple-glazed sealed unit, krypton fill in the cavities (argon doesn't quite get there), warm-edge stainless or composite spacer, and tight tolerance on edge-seal performance. Pane Relief manufactures triple-glazed sealed units to PHI-component specification — drop-in for certified Passivhaus windows from Internorm, Optiwin, Velfac, Smart Architectural Aluminium, and Munster Joinery, and direct-replacement for EnerPHit retrofit of existing aluminium-clad timber frames.
New-build Passivhaus or EnerPHit retrofit
Whether you're aiming at full PHI certification or just the EnerPHit thermal targets, the glass unit is one of three things you can't compromise on (airtightness and continuous insulation are the others). We supply units to the U-value, g-value, and edge-seal numbers PHPP expects, with a coating data sheet shipped on request for your PHPP entry. 10-year edge-seal warranty.
Configure my Passivhaus unitSpecifier, retrofit coordinator, PHI consultant
Net 30 trade accounts. Dedicated Passivhaus desk for spec validation against your PHPP file — we'll cross-check glass U-value, g-value, and psi-installation values before you commit. Coating data sheets, BS EN 1279-5 DoP, and certified PHPP component data on request. Bulk-quote portal for retrofit programmes and large self-build runs.
Trade pricing & bulk ordersWhich Passivhaus glass build do you need?
Five common Passivhaus-spec triple builds, plus a Phbos heritage option. All hit PHI-component or better U-values.
PHI 36mm triple
4mm low-E + 14mm krypton + 4mm clear + 14mm krypton + 4mm low-E. U=0.7 W/m²K, g=0.50. Drop-in for standard Passivhaus aluminium-clad frames.
PHI 44mm triple
4mm low-E + 18mm krypton + 4mm + 18mm krypton + 4mm low-E. U=0.6 W/m²K. Common spec for cold-climate Passivhaus.
PHI + laminated safety
44mm triple with 6.4mm laminated inner pane for low-level critical-location compliance. U=0.6, BS EN 14449 safety class.
PHI + acoustic
44mm triple with 8.8mm acoustic laminated outer. U=0.6 W/m²K, Rw 42-46 dB. Thermal + acoustic for urban Passivhaus.
EnerPHit retrofit triple
36mm triple sized to drop into existing aluminium-clad timber frames during EnerPHit upgrade. Bespoke per-frame measure.
Passivhaus double (slim)
Where triple isn't viable (heritage frames, sash windows), see the Passivhaus double-glazing collection for slim DG that approaches PHI numbers.
Specifying Passivhaus glazing — the things that matter for PHPP
The PHPP heat-balance file expects specific numbers for glass U-value, g-value, and edge psi. Get them wrong and the model doesn't certify.
The 5-point PHI brief
- Centre-pane U-value (Ug): ≤0.80 W/m²K for PHI certification. Pane Relief Passivhaus triples typically hit 0.6-0.7 W/m²K.
- Solar factor (g-value): ideally 0.50 or higher to keep the unit "energy-positive" on south-facing orientations in PHPP. Spectrally selective low-E coatings keep g-value up while keeping U down.
- Light transmittance (τv): aim for ≥70% to keep daylight performance high. Dual low-E triples typically land at 72-74%.
- Edge spacer psi (Ψg): warm-edge stainless or composite spacer (Swisspacer Ultimate, Edgetech Super Spacer TriSeal Premium) gives Ψg around 0.03-0.04 W/mK — critical for the linear edge-loss calc in PHPP.
- Frame weight rating: a 44mm triple is heavy — typically 30-32 kg/m². Confirm your frame is rated for triple-glazing weight before ordering; some legacy timber frames need hinge or sash-cord upgrade.
Pricing & documentation
Prices on this collection are "From £X" at the smallest stock size with PHI 36mm krypton build. Custom sizes and frame-specific drop-in retrofits priced live in the configurator. PHPP-ready coating data sheet (Ug, g, τv, Ψg) shipped on request — no charge.
Passive House triple glazing — common questions answered
Q: PHI vs BFRC — what's the difference and which one do I need?
Two different schemes. BFRC certifies a whole-window WER rating (A++ to E) on a UK climate dataset; it's primarily a marketing and Building Regs label. PHI (Passivhaus Institut) certifies glazing and whole-window components for use inside a PHPP model — a much more rigorous, climate-adjusted, building-physics-based calculation. If you're aiming at Passivhaus or EnerPHit certification, you need PHI-spec glass; BFRC is irrelevant. If you're aiming at Part L compliance only, BFRC is enough.
Q: Argon or krypton — does it really matter?
For triple glazing at PHI U-values, yes. Argon is fine for double glazing (~10% U-value improvement vs air). Krypton has lower thermal conductivity than argon and works well in narrower cavities (12-14mm), which is where you end up when you stack three panes into a sensible frame depth. A 36mm argon triple lands around U=0.85 W/m²K (just below PHI); the same build with krypton drops to U=0.7. For 44mm cavities the gap narrows, but krypton still wins on PHPP.
Q: How heavy is a Passivhaus triple unit?
Approximately 30-32 kg/m² for a 36mm-44mm triple at standard 4mm pane thickness. A typical 1.2m x 1.5m casement unit weighs around 55-60 kg — well within the rating of most modern aluminium-clad Passivhaus frames (Internorm, Optiwin, Velfac all spec to 50+ kg/m²), but at the limit for legacy timber frames. Confirm hinge rating, sash-cord capacity, and frame deflection limits before ordering.
Q: How does triple glazing integrate with MVHR?
Beautifully — that's the whole point of the system design. Triple glazing pushes the inner-pane surface temperature within 1-2°C of room temperature even at -5°C outside, eliminating the cold downdraft you get from double glazing. That means you don't need radiators under windows (a major Passivhaus design move), and the MVHR can deliver heat through trickle ventilation without thermal-comfort complaints. The combination — triple glazing + MVHR + continuous insulation — is what defines Passivhaus thermal comfort.
Q: Will the dual low-E coating affect the appearance?
Slightly. Two low-E coatings (one on face 2, one on face 5 in a triple) reflect more visible light from the outside than a single-coat unit — about 5-7% more reflective. From inside there's no noticeable difference. In bright daylight from outside, the unit reads slightly more reflective and slightly cooler-toned. This is normal and expected, not a defect.
Q: Can I retrofit Passivhaus triple into my existing frames?
Sometimes — depends on three things. (1) Frame rebate depth: you need at least 36mm clear rebate to take a PHI triple; most UK casement frames have only 24-28mm. (2) Frame weight rating: as above — most legacy frames aren't speced for 30+ kg/m². (3) Frame thermal performance: a triple unit in a poor frame is a thermal-bridge disaster; the frame becomes the dominant heat-loss path. For most EnerPHit retrofits we recommend replacing the whole window — but if your frames are aluminium-clad Passivhaus-rated from the original spec, a glass-only triple retrofit can work. Send measurements and we'll advise.
Q: What about condensation on the OUTSIDE of the glass?
Common with very low U-value triple glazing on cold-clear nights — and a sign the unit is working. The outer pane stays so cold (because no heat is leaking out from the warm side) that dew condenses on it from the surrounding humid air. It clears as the sun warms the pane in the morning. No remedial action needed; the warm-edge spacer means the seal is fine.
Q: Lead time for Passivhaus triples?
Stock-size PHI 36mm krypton: 10-14 working days. Custom rectangular: 14-21 working days. 44mm krypton, dual-low-E, or laminated safety builds: 21-28 working days. Acoustic triple builds: 21-28 working days. Plan accordingly — these are not stock items, every unit is built to order and the krypton supply chain is longer than argon.
Q: Do I need to send my PHPP file with the order?
Not required, but it helps. If you (or your Passivhaus designer) send the PHPP file or a screenshot of the glazing input page, our Passivhaus desk will cross-check the glass U-value, g-value, light transmittance, and edge psi against what's on file — and flag any inconsistencies before manufacture. Free service; no consultancy fee. Email trade@panerelief.co.uk with the project reference.
Related guides and specifications
Need spec validation for your PHPP file?
Call the Passivhaus desk on 0117 330 3057 (08:00-18:00 Mon-Fri), or request a quote. Trade and Passivhaus consultancy accounts available.