Hygrothermal behavior of a hemp concrete wall: experimental and numerical study of coating
The aim of this work is to understand the hygrothermal behaviour of hempcrete based on cement at a wall size level. For this both simulation and experimental measurements are conducted in parallel. In the experimental study two Passys test cells are used to compare 2 test walls, subjected to weather solicitations outside and hygrothermal regulation inside. The only difference between walls is the coating, in order to analyse its effect on moisture transfer: one cell is supplied with traditional lime render and the other one with industrial, cement based render. The ability of the coating to regulate relative humidity is shown in this paper. Simultaneously the numerical study is used to calibrate a model to this material in order to have a more complete understanding than the experimental study. A parametric study on material parameters is done to emphasize the impact of coatings, and to analyse the effect of material characteristics’ variation on global behaviour. For this, a coupled heat and moisture transport model is applied with boundary condition from the monitored data (outside and inside). This study show that the hempcrete is sensitive to the applied coating’s properties: in particular, the exterior coating must protect from rain absorption, and be permeable to vapour, otherwise the moisture inside the hempcrete rises, which can reduce the wall performances.