Experimental Investigation of Hygrothermal Parameters of Building Materials Under Isothermal Conditions

Abstract

To determine thermal parameters of porous building materials for building thermal and energy analysis, an experimental study is presently carried out, which applies constant relative humidity controlled by the saturated salt-water solution under isothermal conditions. The principle of isothermal vapor sorption is discussed and the method for temperature and humidity control is proposed. Experiments are first performed using the routine materials of concrete, mortars, and clay brick whose experimental data widely existed in the previous studies, to confirm the present experimental work. Insulation materials of expanded polystyrene, extruded polystyrene, and polyurethane are tested for determining their water vapor permeability and isothermal sorption. These materials are considered due to the fact that they are mostly used as building insulation materials in China but lack thermal-hygro parameters for actual applications. The humidity-bound ranges 11.3—96.7%, which basically covers the whole range of building thermal-hygro environment is encountered. The least square method is used to fit the experimental data obtained, and finally to present regression equations for the three materials. Results of this study are expected to provide key parameters for the model of heat and moisture transfer in the materials for real buildings in hot-summer and cold-winter regions of China, where the transfer of moisture is exhibited significantly in building energy.