Uncontrolled Rh results of southeast 7-Star Australian housing (brick veneer)

This study investigates the effects of uncontrolled indoor relative humidity on interstitial condensation and indoor mould risks in Australia's two most common low-rise timber framed external wall systems, brick veneer and compressed fibre cement sheet cladding of three temperate climate zones. Internationally, hygrothermal and bio-hygrothermal simulations are widely applied to design moisture-resilient building envelopes. In this research, ten-year transient hygrothermal and mould growth simulations are conducted. The result reveals that, without relative humidity control, interior conditions frequently exceed the international recommended 70% threshold, significantly increasing both surface and interstitial mould risks. The results are also compared with continuous control of indoor temperature below 21.1 °C with RH maintained below 70% (per ASHRAE 160) from previous research. Mitigation strategies, including ventilated wall cavities and interior vapour control membranes, are evaluated. Results show 1) frequent exceedances of the 70% RH benchmark in open living areas and bedrooms, with climate-specific variations in mould growth indices. 2) Importantly, vapour control membranes are effective under continuous conditioning, but proved inconsistent performance when under relative humidity was uncontrolled, intermittent conditioning.