Abstract
Wood-based thermal insulation materials have interesting hygroscopic characteristics because of their high moisture capacity. The present paper investigates the moisture conditions in wood-frame walls with wood fibre thermal insulation. The effect of forced convection of moist air into the construction is studied in particular. Laboratory measurements were carried out on a full-scale wall model divided in five sections with various configurations. The wall sections had different combinations of exterior air barrier, thermal insulation and interior vapour retarder. Each section was prepared with an air leakage to simulate supply of moist air to the wall construction through forced convection. The measurement results provided insight in the moisture conditions in the wall and internal distribution of moisture in the wall sections. The results show that walls with wood fibre insulation may have the same risk of high moisture levels as walls with mineral wool insulation. However, the results indicate that wood fibre insulation absorbs condensation and melting water, while the mineral wool does not. Hence, the results imply that the wood fibre insulation has the benefit of distributing the moisture over a larger volume than the mineral wool insulation. Furthermore, the investigations indicate that using an exterior air barrier with high thermal resistance results in a generally lower moisture level in the wall construction, which can be considered favourable regarding risk of mould growth.
Highlights
All the wall sections are influenced by the combination of outward directed vapour diffusion, natural convection and forced con vection making both the relative humidity (RH) (Fig. 5) and the moisture content (MC) (Fig. 6) at the cold face of the insulation layer increasing during the winter periods
The present study has investigated the moisture conditions in wood frame walls with wood-fibre insulation
The results show that walls with wood fibre insulation have the same risk of high moisture levels as walls with mineral wool insu lation
Summary
Growing awareness of environmental sustainability have given increased attention to energy efficiency and emission reduction in the building sector. Thermal insulation for building applications is commonly produced based on materials from petrochemicals (often polystyrene) or minerals (glass or rock) [5]. The general awareness of sustainability has, encouraged an increased focus on thermal insulation based on natural or recycled materials. Wood-fibre based insulation could be beneficial as it may demand less energy during production and may contribute to lower emissions compared to mineral or petrochemical based insulation materials [6,7,8,9], at the same time as inheriting good insulating properties [10,11,12]
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