Moisture Buffering in Surface Materials Due to Simultaneous Varying Relative Humidity andTemperatures: 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 variableindoor environmental conditions. Existing methods looked into the dynamic sorption capacityof materials, by analysing the impact of only humidity fluctuations, with temperature usuallyconsidered non-influential or non variable. However, temperature fluctuations may impact themoisture 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 squarewave fluctuations, which may not be applicable in environments, where the indoor is influencedby 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 undersimultaneous temperature and humidity fluctuations was developed. Clay and gypsum plaster wereanalysed in the numerical model and results were then validated with experimental data. Materialswere subjected to either sinusoidal and triangular temperature and RH variations and different cycletime intervals. The investigation of sinusoidal and triangular environmental variations pushed toa better understanding of materials response to different environments and to the improvement ofthe simplified model. The development of a simplified model can realistically predict the potentialfuture impact of climate changes on buildings without the use of complex and memory demandingcomputational methods.