2026/27 STATUTORY & COST AUDIT • ICO REG ZC136598
A+ Argon Double Glazing (1.2 W/m²K) vs Triple Glazing (0.8 W/m²K): 2026 UK Payback
Is triple glazing worth the extra cost over A+ double glazing in the UK?
Under Approved Document L1B (2026), replacement windows must achieve a whole-window U-value of 1.4 W/m²K or WER Band B. Upgrading from A+ Argon double glazing (1.2 W/m²K) to triple glazing (0.8 W/m²K) adds 18% to 22% (£85–£125 per window) and is primarily justified for north-facing elevations, flight paths, and Busy A-road acoustic damping (38–42 dB Rw).
| Thermal & Acoustic Metric | A+ Argon Double Glazing (28mm) | Triple Glazing (36mm–44mm) |
|---|---|---|
| Whole-Window U-Value | 1.2 W/m²K (Exceeds Part L1B 1.4 Limit) | 0.8 W/m²K (Passivhaus Standard) |
| Typical Supply & Fit Cost (Per Window) | £380 – £520 | £465 – £635 (+22%) |
| Acoustic Noise Reduction (Rw) | 31 – 33 dB | 38 – 42 dB (High Traffic / Flight Path) |
| Annual Gas Heating Saving vs 1990s Glazing | £390 – £520/yr | £455 – £610/yr |
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