About the link between lab-measured material properties and whole building performance simulation: Application to bio-stabilized rammed earth

This article aims to investigate the link between lab-measured material properties and whole building performance of rammed earth (RE) walls through characterization at laboratory scale and numerical simulations using combined heat and moisture transfer models at whole building (WB) scale. RE buildings are known as an energy-efficient solution in hot climates and are low-carbon construction since local unfired earth is used as construction material. Nevertheless, the behavior of such buildings under different internal and external loads needs additional investigations. The present study explores the use of unstabilized RE walls, with and without the use of painting, three bio-stabilized RE and conventional concrete walls for comparison. The simulation includes climate conditions from Central Europe and North Africa, along with typical residential and tertiary occupancy scenarios. To identify the contribution of RE materials in controlling the indoor climate, the investigation covers a total of 24 configurations of six wall materials, two locations, and two occupancy scenarios. Results are analyzed by comparing heating demand, summer thermal comfort, and relative humidity levels. Furthermore, the hygrothermal properties of bio-stabilized RE are experimentally determined, to confirm the choice of using only moisture-dependent parameters. Experimental investigations focus on the influence of temperature on sorption isotherm, hysteresis, adsorption kinetics, and moisture buffer value (MBV). The results of this investigation show that thermal properties measured at the material scale seem to have a direct link with results at the whole building scale for heating demand and summer thermal comfort for uninsulated walls, while a more complex behavior is related to the hygroscopic properties, due mainly to the combined effect of the kinetics of adsorption and vapor permeability of the material.