Moisture permeability measurement using a surface air dew-point probe: A feasibility study

Moisture permeability of building materials is essential information to predicting moisture transfer in buildings. The conventional way of measuring the permeability of a material is the standard cup test method, which is very time consuming. The paper describes an investigation into the feasibility of using a surface air dew-point probe (SADP), which was first designed by Tsuchiya, to significantly shorten the measurement time. An analysis is presented to show the degree of accuracy required of the measurement of the moisture content changes of the air flowing through the SADP in order that accurate measurement of permeability can be achieved. The requirement, however, may not be achievable with the dewpoint temperature sensors currently available. An experimental method for solving this problem is suggested, based on experience gained in trial experiments.