Characterization of a novel bio-insulation material for multilayer wall and research on hysteresis effect

In this work, the hygrothermal properties of a novel bio-insulation material made of magnesium phosphate cement (MPC) and corn stalk (CS) were measured and compared with three excellent materials (date palm concrete, hemp-lime concrete and rape straw concrete) from previous study. To analyze the hygrothermal behavior of MPC-CS as the exterior insulation layer of multi-layer wall. The numerical model for multilayer walls with different bio-insulation layers was established to study the coupled heat and moisture transfer under real summer and winter climatic conditions. Furthermore, the effect of hysteresis on the hygrothermal behavior of external insulation multilayer walls was investigated. The results showed that multilayer wall containing MPC-CS insulation layer can better regulate temperature (T) and relative humidity (RH) variations, especially during the wintertime. When the hysteresis effect is taken into account, the accuracy of calculation will be improved. For highly dependent materials, it is necessary to calibrate the sorption isotherms to obtain more accurate results. However, as the depth of multilayer wall increased, the influence of hysteresis gradually decreased.