Nonisothermal moisture diffusion in porous building materials

The hygrothermal performance of building envelopes has been the subject of intensive research over the past decade, culminating in the development of a series of advanced computer-based simulation models. However, in spite of the considerable progress that has been made, a question which is not, as yet, fully resolved is the coupled effect of temperature gradient on moisture diffusion rates. As a result, the material transport data used as input for these models is generally determined from isothermal permeability measurements. This paper describes two investigations in which moisture flux experiments were carried out on small-scale material samples subjected to gradients in both temperature and humidity. In each case a different experimental technique was used and different materials were tested. An analysis of the results was undertaken in an attempt to identify the significance of any temperature-driven transport compared to the concentration-driven component.