Hygrothermal performance and water vapour diffusion resistivity of Australian plantation-grown timber

This research investigates the hygrothermal performance of Cross-Laminated Timber (CLT) and solid wood products manufactured from Australian plantation-grown timber. Over the past three decades, the use of plantation softwood and hardwood, and engineered wood products in Australian buildings has increased. However, wood products can also provide a food source for mould growth in inappropriately designed or constructed façade systems, highlighting the need for accurate risk assessments concerning moisture transport, structural degradation, and adhesive failure. Understanding water vapour diffusion resistivity is crucial for conducting hygrothermal simulations, which support the design of moisture-resilient timber-based façades. This research explores water vapour diffusion resistivity in timber, identifying gaps in Australian plantation timber research. It examines laboratory-based methods for quantifying water vapour diffusion resistivity and approaches to validate hygrothermal simulations in full-scale buildings. The study highlights multi-RH gravimetric cup testing as the most effective method for improving hygrothermal modeling accuracy and moisture risk assessments. By establishing high-quality water vapour diffusion resistivity data, this research supports building professionals and regulators in making informed decisions, leading to energy-efficient, healthy, and durable buildings and promotes renewable timber resources in modern construction. This research contributes to industry best practices and regulatory advancements in timber-based construction.