A dynamic hysteresis model of heat and mass transfer for hygrothermal bio-based materials

The hygrothermal behaviour of porous building materials is significantly determined by the moisture and heat transfer phenomena. However, most of existing models used to predict this phenomenon neglect moisture hysteresis effect and dynamic capillarity effect, limiting their accuracy in assessing the efficiency and sustainability of bio-based building materials. To bridge this gap, the model presented in this paper considers both dynamic and hysteresis effects. The Finite Element Method (FEM) is adopted for the discrete approximation of the partial differential equations governing heat and moisture transfer. The model is validated with respect to experiment performed on bio-based material subjected to thermo-hygrical boundaries conditions. Results show unequivocally that dynamic capillarity effect and moisture hysteresis effect should be considered simultaneously to quantify hygrothermal behaviour of porous building materials. This critical insight underscores the significance of this research, offering a comprehensive model for evaluating the efficiency and sustainability of these materials by addressing the often-neglected aspects of moisture behaviour, i.e., dynamic and hysteresis effects. This model is marked by its precision and thorough consideration of essential factors, making it an indispensable contribution to the field and advances the understanding of the hygrothermal behaviour of bio-based building materials in real conditions. It would help in designing optimized building envelop.