London · Q2 2026 · Triple Glazed
Passivhaus Windows London
What counts as a Passivhaus window
Passivhaus is a building energy standard, not a window brand. To meet it, the whole-window U-value (Uw) must hit ≤0.80 W/m²K in the UK 'cool, temperate climate' rating, with thermal-bridge-free installation. EnerPHit (the retrofit standard) is slightly more lenient at ≤0.85 Uw. The standards both depend on three things working together: the frame, the glass, and the install detail.
| Standard | Window Uw | Airtightness | Typical UK use |
|---|---|---|---|
| Passivhaus (cool-temperate) | ≤0.80 W/m²K | ≤0.6 ach@50Pa | New-build, certified |
| EnerPHit (retrofit) | ≤0.85 W/m²K | ≤1.0 ach@50Pa | Deep retrofit, listed-friendly |
| Building Regs Part L 2025 | ≤1.4 W/m²K | ≤8 ach@50Pa | UK statutory baseline |
| Future Homes Standard 2025+ | ≤1.2 W/m²K target | ≤5 ach@50Pa | England, new dwellings |
Compliant frame systems
Below: the systems we work with that hit Passivhaus or EnerPHit performance. AWS 70.HI sits at the threshold for EnerPHit; AWS 75.SI+ is the cleanest fully-Passivhaus alu choice. Internorm and Optiwin imports are timber-aluminium composites with the lowest U-values available.
| System | Type | Uw (best) | Certification |
|---|---|---|---|
| Schüco AWS 75.SI+ | Aluminium | 0.76 W/m²K | PHI cool-temperate certified |
| Schüco AWS 70.HI | Aluminium | 0.84 W/m²K | PHI cool-temperate (borderline) |
| Internorm KF410 | Timber-aluminium composite | 0.66 W/m²K | PHI cool-temperate certified |
| Optiwin Resista | Timber | 0.65 W/m²K | PHI cool-temperate certified |
| Velfac Helo Plus | Timber-aluminium composite | 0.79 W/m²K | PHI cool-temperate certified |
| Veka Softline 82 | uPVC (purpose-built) | 0.79 W/m²K | PHI cool-temperate certified |
The glass spec that gets you there
Frame alone won't hit Passivhaus. The glazing make-up is the second half of the equation. Standard certified Passivhaus glazing is a triple-glazed, krypton-filled unit with two soft-coat low-e coatings and warm-edge spacers.
| Spec | Make-up | Ug | Notes |
|---|---|---|---|
| Standard double glazing | 4/16/4 argon | 1.1 W/m²K | Building Regs minimum, not Passivhaus. |
| High-performance DG | 4/18/4 argon, 2× low-e | 1.0 W/m²K | Best DG can do — still not Passivhaus. |
| Triple, argon | 4/16/4/16/4 argon | 0.7 W/m²K | EnerPHit-suitable; borderline for full Passivhaus. |
| Triple, krypton | 4/16/4/16/4 krypton | 0.5–0.6 W/m²K | Standard Passivhaus glazing spec. |
| Spacer (warm-edge) | Swisspacer Ultimate / Edgetech Super Spacer | — | Required — aluminium spacers cold-bridge. |
Install detail — the thing nobody photographs
A certified Passivhaus window installed badly will not perform. The biggest avoidable losses come from the install detail, not the product spec. Here's what a competent install looks like:
| Frame seated on insulated sub-frame (Compacfoam, Purenit) — no direct contact with cold-bridging steel lintel. |
| Thermal-break of frame aligned with thermal-break of wall insulation (centre of insulation, not face of structure). |
| External tape: weather-tight, vapour-permeable (Tescon Profect or Pro Clima Solido). |
| Internal tape: airtight, vapour-control (Pro Clima Contega Solido or Tescon Vana). |
| Reveal lining insulation continuous to plaster line — no thermal-bridge bypass at jamb or head. |
| Pre-install blower-door test (where targeting full Passivhaus) to baseline existing leakage. |
| Post-install blower-door verification, smoke-pencil at every frame perimeter. |
| Photographic install record retained for Passivhaus certifier sign-off. |
Passivhaus window fitted prices
London Q2 2026, fitted, including triple glazing, airtightness tape detail, removal of existing window, and FENSA self-certification. Premium over standard alu is typically 30–50%.
| Configuration | System | Low | High |
|---|---|---|---|
| Casement (single sash) | Schüco AWS 75.SI+ | £1,800 | £2,600 |
| Casement (twin sash) | Schüco AWS 75.SI+ | £2,400 | £3,200 |
| Tilt-turn | Schüco AWS 75.SI+ | £2,200 | £3,200 |
| Casement (timber-alu) | Internorm KF410 | £2,200 | £3,800 |
| Large picture / fixed | Schüco AWS 75.SI+ | £3,500 | £7,000+ |
| EnerPHit casement | Schüco AWS 70.HI | £1,400 | £2,400 |
| Blower-door test (extra) | — | £600 | £1,200 |
Frequently asked
What is a Passivhaus window?
A Passivhaus window meets the Passivhaus Institute's component standard for low-energy buildings. For a UK 'cool, temperate climate' rating, the whole-window U-value (Uw) must be ≤0.80 W/m²K, with thermal-bridge-free installation and certified airtightness. In practice that means a triple-glazed krypton-filled unit with warm-edge spacers in a high-insulation aluminium, timber, or composite frame.
What's the difference between Passivhaus and EnerPHit?
Passivhaus is the standard for new-builds — Uw ≤0.80 W/m²K windows in cool climates, alongside airtightness ≤0.6 ach@50Pa and stringent thermal-bridge limits. EnerPHit is the retrofit standard, slightly more lenient: Uw ≤0.85 W/m²K is typically accepted because retrofit walls and floors limit overall achievable performance. Most London projects targeting deep retrofit aim for EnerPHit rather than full Passivhaus.
Which windows meet the Passivhaus standard?
In aluminium: Schüco AWS 75.SI+ (0.76 Uw — fully certified for cool climates) and AWS 70.HI (0.84 Uw — borderline, EnerPHit-suitable). In composite/timber-aluminium: Internorm KF410 (0.66 Uw), Optiwin Resista, and Velfac Helo Plus. All are Passivhaus Institute Component Certified. Standard UK uPVC windows do not meet Passivhaus — purpose-built Passivhaus uPVC frames (e.g. Veka Softline 82) are an exception.
How much do Passivhaus windows cost in London?
Certified Passivhaus windows carry a 30–50% premium over standard aluminium. Schüco AWS 75.SI+ casements run £1,800–£3,200 fitted per window in London 2026. Internorm KF410 imports run £2,200–£3,800 per window. Large fixed/picture units £3,500–£7,000+. Prices include VAT, fitting, airtightness tape detail, removal, and FENSA self-certification. Triple-glazed krypton-fill is standard.
What glass is used in Passivhaus windows?
Standard Passivhaus glazing is a triple-glazed unit with two low-e coatings and krypton fill: 4mm/16mm/4mm/16mm/4mm with warm-edge spacers (Swisspacer Ultimate or Edgetech Super Spacer). Glass-only Ug is 0.5–0.6 W/m²K. Argon-filled triple glazing reaches 0.7 Ug — acceptable on EnerPHit but borderline for Passivhaus.
Why is the install detail so important?
A certified Passivhaus window installed badly will not perform. Thermal-break continuity from frame into wall insulation is critical — frames seated directly on cold-bridging steel lintels create condensation and waste much of the window's insulation. Airtightness depends on continuous tape detail (external rain-tight, internal vapour-tight). Most Passivhaus projects also require pre- and post-blower-door testing to verify the install.
Does Apex Glazing do certified Passivhaus installation?
Apex Glazing has installed AWS 70.HI on a Passivhaus-targeting retrofit in north London where airtightness tape detail and thermal-bridge-free install were required. We are not currently certified Passivhaus tradespeople (CEPH/CEPHC), so on full Passivhaus certification projects we work alongside the project's Passivhaus designer and airtightness consultant. For EnerPHit and high-performance retrofits without certification, we install AWS 75.SI+ and AWS 70.HI to manufacturer install detail end-to-end.
Can I install Passivhaus windows in a listed building?
Listed buildings are usually limited to like-for-like replacement of original windows — typically timber sash. Modern Passivhaus aluminium and composite windows are rarely approved on listed properties. The exception is rear or side elevations not visible from the street, where Listed Building Consent may permit modern fenestration. For listed front elevations, secondary glazing is the more realistic upgrade route — see our secondary glazing London page.
