Laboratory experiments on hygrothermal behaviour of real-scale timber walls

Hygrothermal performance of massive wood and wooden materials used as structural purposes in building envelope are measured by means of laboratory tests. For this purpose, hygrothermal short-time behaviour of two massive timber walls exposed to summer climatic conditions were investigated. A double climatic chamber simulating real on-site conditions was designed and built at the LERMAB/ENSTIB site in Epinal and used during wall behaviour assessment. Temperature and humidity variations with time were measured at different locations to determine profiles evolution of the investigated wall layers. Our results showed a contribution of wood and wooden insulation products in improving indoor thermal climate, as these materials allow a decrease and a significant delay of the important temperature variation of outdoor climate. Laboratory result was also compared to field measurement for the cross-laminated wall system, time lag values for north and south walls showed that solar radiation have a non negligible effect on temperature propagation within the wall. The variation of absolute humidity of the air in the cavity around humidity sensors installed in wall layers shows significant dependence with temperature variation. This phenomenon is consistent with the storage or realising of humidity during hygroscopic equilibrium between wood-based materials and its surrounding air.