Passive House triple-glazed alu-clad windows
To meet Ireland's NZEB (Nearly Zero Energy Building) Part L standard on a new build or Certified Passive House ( ≤ 0.80 W/m²K), triple-glazed alu-clad windows combine a 48mm double low-E argon glass unit (Ug 0.5 W/m²K) with an insulated timber-core frame to deliver a whole-window Uw of 0.75 to 0.82 W/m²K.
Glass g-values for solar gain, warm-edge Swisspacer bars, and how 3-layer airtightness tape installation passes the 0.6 ACH50 blower-door test.
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Inside a 0.78 W/m²K Passive alu-clad window
| Component | Standard A-rated double glazing | Passive-grade triple-glazed alu-clad |
|---|---|---|
| Glass unit configuration | 4mm / 16mm Argon / 4mm Low-E (24mm) | 4mm Low-E / 18mm Argon / 4mm / 18mm Argon / 4mm Low-E (48mm) |
| Centre-pane U-value (Ug) | 1.1 W/m²K | 0.50 to 0.53 W/m²K |
| Whole-window U-value (Uw) | 1.25 to 1.40 W/m²K | 0.75 to 0.82 W/m²K (EN ISO 10077-1) |
| Solar energy transmittance (g-value) | 0.62 to 0.65 | 0.50 to 0.54 (high solar-gain low-E coating) |
| Edge spacer bar | Aluminium or basic composite | Swisspacer Ultimate (Ψg ≤ 0.030 W/mK) |
| Airtightness classification | Class 4 (EN 12207) | Class 4 with triple perimeter EPDM compression seals |
Why a 0.78 W/m²K window fails without 3-layer airtightness taping
On an Irish self-build or deep retrofit aiming for an airtightness blower-door test result below 1.5 m³/(h·m²) (or 0.6 ACH50 for Passive House), expanding polyurethane foam alone is not an airtight seal. Specialist alu-clad installation teams use a 3-layer RAL perimeter sealing system:
- Outside (weather tight, vapour permeable): Pre-compressed expanding compriband tape (such as Illbruck TP600) or breathable external membrane stops driving Atlantic rain while allowing any moisture in the wall joint to dry outwards.
- Middle (thermal & acoustic core): Flexible low-expansion elastic PU foam or mineral wool packing fills the 12mm–15mm structural tolerance gap around the frame.
- Inside (100% vapour and airtight): Continuous internal airtightness tape (such as Siga Fentrim or Pro Clima Contega) bonds the back of the timber window frame directly to the plastered blockwork or internal vapour-control membrane before the reveals are skimmed.
What alu-clad windows cost in Ireland
Our supply-and-fit price guide per window, per square metre and for full retrofit or self-build house packages.
| Job | Typical cost | What moves the price |
|---|---|---|
| Standard alu-clad casement or tilt-and-turn window (triple glazed) | €1,100 to €2,000 per window | Uw 0.78–0.85 W/m²K · engineered Nordic pine + powder-coated alu |
| Large fixed picture or floor-to-ceiling alu-clad screen | €1,400 to €2,800 per opening | 44mm–52mm toughened triple unit · slim 55mm frame |
| Alu-clad lift-and-slide patio door (2.4m–3.6m) | €4,200 to €7,800 | Low-threshold fibreglass/aluminium track · up to 300kg sash gear |
| Alu-clad French patio doors or entrance door | €2,800 to €4,900 | Multi-point security locking · matching internal timber finish |
| 3-bed semi-detached full house (8–10 alu-clad windows) | €11,000 to €20,000 | After €3,000 SEAI grant (if pre-2011): €8,000 to €17,000 |
| 4-bed detached / self-build package (12–16 windows + sliding door) | €16,500 to €32,000 | After €4,000 SEAI retrofit grant: €12,500 to €28,000 |
| Solid European oak or ash interior upgrade (vs Nordic pine) | +18% to 25% | Clear-lacquered hardwood interior with extruded aluminium exterior |
| Per square metre installed (triple-glazed alu-clad) | €1,000 to €1,500 per m² | Includes airtightness tapes, compriband and 13.5% supply-and-fit VAT |
Real examples and installation detail
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Questions homeowners & self-builders ask
Should I use solar-control glass on south-facing alu-clad windows in Ireland?
On rooms where glazing exceeds 25% to 30% of floor area facing south or west, Ireland's DEAP/Part L overheating check (TGD L) often requires a lower solar factor (g-value ~0.35 to 0.42) on large south/west picture screens while keeping high-solar-gain glass (g-value ~0.53) on north and east windows.
How heavy is a triple-glazed alu-clad window?
Triple glazing with three 4mm panes weighs 30 kg/m², and with 6mm toughened safety panes weighs 45 kg/m². Alu-clad frames use deep laminated timber sections and heavy-duty concealed hinges or craned vacuum-lifters for large fixed screens.
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