An empirical measurement of the water vapour resistivity properties of typical Australian pliable membrane

International experience has shown that the duo of better insulated and more air-tight envelopes has often demonstrated an increased potential of moisture accumulation, interstitial condensation, and mould growth within the building envelope. Recent Australian research has documented high levels of indoor relative humidity and moisture accumulation in external walls. It is accepted that the materials that comprise the external envelope play a pivotal role in managing moisture accumulation and household generated water vapour diffusion. Internationally, to inform external envelope design, long-term transient hygrothermal analysis tools are used to simulate the water vapour diffusion and moisture accumulation process. To complete the hygrothermal analysis, the water vapour resistance properties of each envelope component must be known. At this stage, the vapour resistivity properties of most Australian construction materials are unknown. In this research, the vapour resistivity properties for some selected pliable membrane materials has been tested using variable relative humidity and variable temperature conditioned room. This novel method has been developed in response to international concern that the current vapour resistivity testing method may be inadequate, due to the variable conditions that exist within new buildings. This paper reports on the results from tests completed at 23oC and relative humidity values of 35% and 50%.