ABSTRACT
The experimental determination of the moisture transfer characteristics of building materials is an important requirement for the successful application of moisture simulation models. However, there is a general lack of reliable and repeatable experimental data, which often leads to extrapolation and estimation techniques being employed. These factors can undermine the accuracy of moisture predictions and, in extreme cases, could lead to incorrect and potentially costly conclusions about the integrity of a construction. The measurement of moisture transfer coefficients is generally carried out by means of gravimetric test methods, which are well recognised as being prone to many experimental difficulties due to the lengthy test periods involved. In an attempt to overcome these long test durations, and also to provide more useful information, an alternative approach to standard methods of measuring material moisture permeability and moisture content has been developed. This new approach involves carrying out gravimetric tests within an environment of reduced barometric pressure. Conducting tests in this way not only reduces the experimental period, but also facilitates the separation of the measured moisture flux into its vapour and liquid components.
