Should timber frame insulation be breathable?

Yes, strongly recommended. Breathable (vapour-permeable) insulation allows moisture vapour to pass through the wall assembly and dry to the outside, reducing the risk of interstitial condensation and timber decay.

Yes, strongly recommended. Breathable (vapour-permeable) insulation allows moisture vapour to pass through the wall assembly and dry to the outside, reducing the risk of interstitial condensation and timber decay. This is particularly important in timber frame construction where trapped moisture can cause structural damage. Breathable insulation materials include: mineral wool, wood fibre, cellulose, and sheep wool. Non-breathable materials (PIR, EPS, XPS) can be used but require careful vapour control layer design and carry higher moisture risk if the VCL is imperfect.

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

Related questions

• What is the best insulation for a timber frame house?
• What U-value should a timber frame wall achieve?
• Can I use PIR insulation in a timber frame?

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.