What insulation is used with CLT walls?

CLT walls are typically insulated externally with mineral wool, wood fibre, or rigid PIR/phenolic insulation. A common wall build-up is: internal CLT panel (100–160 mm) + vapour control layer + insulation (100–200 mm) + breather membrane + ventilated cavity (25–50 mm) + external cladding.

CLT walls are typically insulated externally with mineral wool, wood fibre, or rigid PIR/phenolic insulation. A common wall build-up is: internal CLT panel (100–160 mm) + vapour control layer + insulation (100–200 mm) + breather membrane + ventilated cavity (25–50 mm) + external cladding. This achieves U-values of 0.15–0.20 W/m²K. Internal insulation is avoided because it reduces the thermal mass benefit of exposed CLT and creates interstitial condensation risk.

Why this matters

This question relates to CLT Modular Construction: How Cross-Laminated Timber Homes Are Built, 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:

→ CLT Modular Construction: How Cross-Laminated Timber Homes Are Built

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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. All technical content is reviewed by qualified timber technologists before publication.