Development of a novel method to establish the hygrothermal water vapour resistance factor of construction materials for moisture management design of buildings

For nearly a century, it has been acknowledged that the nexus of envelope design, material choices and interior conditioning patterns can lead to surface and interstitial mould and condensation. Both of which affect building durability and occupant health. In Australia, the development of hygrothermal building regulations has been deferred based slow, which has resulted manufacturers reticence to obtain and publish construction material hygrothermal properties, such that high quality hygrothermal simulations can occur. This paper reports the results of the research completed to develop a novel methodology for acquiring high-quality water vapour diffusion resistivity data for input into hygrothermal simulation software. The method involves establishing a new hygrothermal laboratory, international round robin validation of the new laboratory and the design of a new experimental methodology to quantify relative humidity dependent water vapour diffusion resistivity properties for construction materials. Construction material relative humidity dependent hygrothermal boundary curves were established, using a new harmonic adjustment method. Hygrothermal simulations were then completed using single point and multivariable relative humidity water vapour diffusion resistivity values. The results show that there are significant differences in simulated moisture accumulation and the mould growth risk between hygrothermal simulations using single point and multi-point water vapour diffusion resistivity values.