Condensation and mould growth risk in nature-based insulating materials integrated in a timber-based wall system.

This study is written as a part of the Build-in-Wood project, in cooperation with the Norwegian Institute of Wood Technology. The goal was to evaluate the condensation and mould growth risk in flax fibre, wood fibreboard and mineral wool, integrated in a timber-based wall system. In addition, it was investigated if the exterior cladding and the convection in the air gap behind the exterior cladding affects the condensation and mould growth risk. The investigations were conducted through experiments and both short-term and long-term numerical simulations, where the short-term simulations were conducted for validation. Both the experimental investigations and the numerical simulations revealed that there is no significant risk for condensation and mould growth in any of the materials. For properties like thermal transmittance and absolute humidity, all materials seem to be within the requirements, and suitable for use in a timber-based wall, even though there were some differences between the materials. Mineral wool had the lowest thermal transmittance, and flax fibre had the highest. In addition, wood fibreboard stood out with a bit higher absolute humidity than the rest of the materials. Nevertheless, both flax fibre and wood fibreboard can be considered good alternatives when choosing insulating material