A logical extension of the ASTM standard E96 to determine the dependence of water vapour transmission on relative humidity

摘要

It is well known that the water vapour transmission properties of hygroscopic building materials depend on the local relative humidities(rh). Traditionally, the ASTM Standard E96 specifies only two conditions of rh. The dry cup method in the standard corresponds to a mean rh of 25 percent and the wet cup to 75 percent. This information is not enough to describe the behaviour of the material through the entire range of rh. European standards have already proposed an extension of the existing standard to address this issue. ASTM standard should follow this change. A logical extension of the E96 standard to include the effect of rh on water vapour transmission properties has been proposed and is being discussed by one of the C16 Committee Task Groups.