Standard: Building Regulations, Approved Document L (June 2022 update).
Required U-values
- External wall: ≤ 0.18 W/m²K
- Roof: ≤ 0.11 W/m²K
- Ground floor: ≤ 0.13 W/m²K
Climate
Heating Degree Days (HDD): 2,300 (UK average).
Typical energy price (for savings estimation)
Natural gas: ~0.07 GBP/kWh (Ofgem reference, 2025–2026).
These values are used as defaults in the insulation calculator — you can override the energy price field.