A novel method to determine the water vapour permeability of composite porous materials

This study introduced a novel method to determine the water vapour permeability of composite porous materials. The permeability of a composite material as a combination of porous solid-phase with micropores and gas-phase with macropores in a unit cell of material was evaluated. The method mainly considered element structure models for total porous materials and the density-concentration averaging method for the porous solid phase. Literature comparison results show that the element structure model can clearly reflect the characteristics of permeability variations with porosity. The verification results of literature experiments show that the permeability of composite porous materials can be effectively predicted with an average error 13% when the density-concentration averaging method of porous solid-phase was introduced into the element structure model. For highly porous materials, a higher increase in the porous solid-phase permeability coefficient did not significantly change the overall permeability of the material. The results show that the porous materials with cylindrical and circular truncated cone pores have poor permeability enhancement potential. In general, this study provides a reliable experimental supplement method for determining the water vapour permeability, which can guide the design of new materials, the optimization of building envelope and the simulation of energy consumption in building environment.