Multi-scale analysis of the effects of hysteresis on the hydrothermal behaviour of bio-based materials: Application to hemp concrete

Experimental measurements of sorption isotherms show a difference between the water contents in theadsorption phase and the desorption one. This is mainly due to the hysteresis phenomenon. Not considering thisphenomenon in hygrothermal behaviour models impacts the reliability of the latter. In this paper, we havestudied the effects of hysteresis on the hygrothermal behaviour at the building scale. For this purpose, a newimplementation method of a hysteresis model was proposed and validated at the material and wall scales using abi-climatic chamber which controlled the indoor and outdoor climate conditions. Then, the effect of the hysteresisphenomenon at the building scale was evaluated following a COMSOL/TRNSYS co-simulation approach toconsider the gains and losses in the hydric fluxes going through walls. The results showed significant differencesin terms of the relative humidity of the living environment. However, no difference was noticed in the temperaturevariations. On the other hand, the total heat fluxes were also affected by the hysteresis phenomenon dueto latent heat parts, that were driven by variations in relative humidity. The maximum gain and loss discrepancies(with and without hysteresis) in total heat fluxes of 1121 kJ/h and 1086 kJ/h, respectively, were obtainedduring the first week of February (winter period). The results also revealed that these discrepancies are sensitiveto the number of persons in the living environment