Behavior of a hemp-based concrete wall under dynamic thermal and hygric solicitations

Here we document the behavior at wall scale of a hemp-based hygroscopic material under various temperature and moisture dynamic conditions. The wall was made of precast hemp concrete (HC) blocks with air cavities. It was tested within a bi-climatic chamber and monitored thanks to hygrothermal sensors in the wall and in the chambers. The results from an in-house heat and moisture transfer model were compared to the experimental data, using the actual thermal and hygric characteristics of the hemp-based material determined in a previous study. The experiments allowed to demonstrate how the heat and moisture transport phenomena within the wall are coupled, particularly how a temperature difference can be a sufficient driving force for the release of moisture. The work points out the impact of moisture adsorption on heat release and on the temperature changes within the wall. Finally the numerical model served also to the modelling of an equivalent wall made of concrete to help highlighting the moisture dumping capability of the bio-based material, together with its thermal insulation capacity.