The walls of buildings experience heat, air and moisture transfers. These transfers have a significant influence on indoor climate, since they affect the value of temperature and relative humidity inhouses. High levels of humidity lead to pathologies in the buildings, and influence the air quality and the hygrothermal comfort of the occupants. In this work, a numerical analysis of the behaviour of polystyrene mortar under hydric solicitations was led. The simulations were held using ComsolMultiphysics and MATLAB. There were two different moisture transfer models used in this work: the first one took into account sorption hysteresis phenomenon, and the other one did not. The computed results showed that considering sorption hysteresis in modelling the hydric behaviour of the material allows obtaining more accurate results comparing to a model that does not consider hysteresis.