What U-value should a timber frame wall achieve?

Building Regulations Part L 2025 requires a maximum wall U-value of 0.18 W/m²·K for new dwellings. However, best practice for timber frame homes targets 0.12–0.15 W/m²·K, and passive house standard requires 0.10–0.12 W/m²·K.

Building Regulations Part L 2025 requires a maximum wall U-value of 0.18 W/m²·K for new dwellings. However, best practice for timber frame homes targets 0.12–0.15 W/m²·K, and passive house standard requires 0.10–0.12 W/m²·K. A standard 140 mm timber frame with mineral wool between studs achieves approximately 0.25 W/m²·K — additional insulation (external, internal service void, or both) is needed to meet current regulations. A 140 mm frame + 50 mm service void + 80 mm external insulation achieves approximately 0.13 W/m²·K.

Why this matters

This question relates to Insulation for Timber Frame Homes: Materials & Performance Comparison, which covers the broader topic in detail. Understanding this specific aspect helps architects, builders, and timber dealers make informed specification decisions.

For full context and additional technical detail, see our comprehensive guide:

→ Insulation for Timber Frame Homes: Materials & Performance Comparison

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About this answer

This answer is part of the PuurModulair Knowledge Base — comprehensive timber specification guidance for architects, builders, and dealers across the UK, EU, and Scandinavia.