Total Pressure Gradient Incidence on Hygrothermal Transfer in Highly Porous Building Materials

Abstract

A new experimental investigation is conducted to extract conclusions about the magnitude of moisture transfer due to the total air pressure difference, generally, caused by wind or pressurization by ventilation, on hygroscopic porous wall. A special constructed setup tolerating the creation of low total pressure gradient at different relative humidity conditions is performed. The resulting moisture flux and the hygrothermal state around and within the material are monitored. Then, a characterization of the intrinsic moisture infiltration coefficient is defined. This coefficient is used as an input parameter in simulation models. The experimental procedure points out diverging conclusions between different testing materials (wood fibrous insulation, OSB and aerated concrete). In fact, the amount of moisture infiltration is completely dependent on both combination of total pressure gradient value and hygrometry of the specimen. It has an important contribution on the moisture transfer, in walls, relatively to that induced by vapor diffusion phenomenon.