Hygro-Thermal Modelling of Earthen Materials for Building Applications

Earth is a building material with low carbon emissions compared to conventional concrete or fired bricks. Earthen materials have an excellent capacity to regulate indoor hygrothermal conditions allowing for a better comfort with reduced heating and cooling needs during the life cycle of the building. The present paper presents a theoretical framework to investigate the hygro-thermal response of earthen materials by coupling the principles of unsaturated soil mechanics combined with the thermodynamics of porous media. The degree of coupling between the two variables (temperature and relative humidity or water content) depends on the values of the water and vapour permeability functions which, in turns, depend on the water retention curve of the material. Results shows that, in the hygroscopic domain, the hydro-thermal coupling is more influenced by the saturated permeability than by the vapour diffusion coefficient.