Experimental and numerical analysis of the transient hygrothermal behavior of multilayered hemp concrete wall

A coupled heat and moisture transfer 1D-model is developed to simulate the hygrothermal behavior of a coated hemp concrete wall. The hysteretic behavior of each layer (hemp concrete and plasters) is included in the modeling whereas a perfect hygrothermal contact is assumed between each layer. The numerical results are first compared to experimental ones obtained on a facility specially designed to measure mass variations as well as temperature and relative humidity fields within a coated sample. The comparison gives satisfactory results and underlines the influence of the hygrothermal properties, but also of plaster's thickness. Furthermore, it is observed experimentally that coating layers reduce moisture transfer and, thus, moisture buffer value of multilayered materials. A second comparison is performed with experimental data measured on a multilayer wall subjected to climatic variations. It was found that including the hysteresis in the modeling improve the prediction of the relative humidity field within a wall subjected to isothermal and non-isothermal conditions. However, it requires knowing the hygrothermal history of the wall in order to set initial moisture content of each layer.