Moisture buffering in surface materials due to simultaneous varying relative humidity and temperatures: Experimental validation of new analytical formulas

Buildings are subjected to the indoor environment, especially in non-controlled climates. Temperature and humidity variations might effect or even damage materials sensitive to moisture. For this reason, it is important to understand the response of hygroscopic materials to variable indoor environmental conditions. Existing methods looked into the dynamic sorption capacity of materials, by analysing the impact of only humidity fluctuations, with temperature usually considered non-influential or non variable. However, temperature fluctuations may impact the moisture capacity of the materials, as materials properties might substantially vary with temperature. Moreover, in existing protocols, the humidity variations are considered to be varying under square wave fluctuations, which may not be applicable in environments, where the indoor is influenced by daily and seasonal climate variations, which presents more complex fluctuation. In this study, a simulation method that can predict the impact of environmental condition on materials under simultaneous temperature and humidity fluctuations was developed. Clay and gypsum plaster were analysed in the numerical model and results were then validated with experimental data. Materials were subjected to either sinusoidal and triangular temperature and RH variations and different cycle time intervals. The investigation of sinusoidal and triangular environmental variations pushed to a better understanding of materials response to different environments and to the improvement of the simplified model. The development of a simplified model can realistically predict the potential future impact of climate changes on buildings without the use of complex and memory demanding computational methods.