Intermittently Controlled Temperature: A Hygrothermal and Bio-hygrothermal Assessment of Timber-framed Brick Veneer Wall Systems

This study examines indoor temperature profiles in intermittently conditioned 7-Star homes in south-eastern Australia, focusing on two common external wall systems: brick veneer and compressed fibre cement sheet. Two scenarios are evaluated: (1) continuously controlled indoor temperature and relative humidity (RH), as prescribed by ASHRAE 160, and (2) uncontrolled indoor temperature with regulated RH. The study also assesses the effectiveness of mould mitigation strategies, including ventilated wall cavities and vapour control membranes, under both thermal conditions. The findings indicate frequent exceedances of the 21.1 °C threshold, particularly in kitchen–living spaces and bedrooms, leading to varying mould risks across climate zones. Mitigation effectiveness also varied: in several cases, an interior vapour control layer increased mould risk under uncontrolled temperature conditions, contrary to its performance in continuously conditioned settings.