The aim of this work is to examine the hygrothermal performance of timber-based envelopes across Australia. The heat and moisture (HAM) analyses are performed with consideration of various climatic conditions for all major Australian cities including: Darwin (zone 1); Brisbane (zone 2); Sydney (zone 5); Melbourne (zone 6); and Canberra (zone 7). Two main typical wall sections are selected for investigation, a massive CLT wall type with an external insulation layer and a cavity-insulated timber frame wall. The transient hygrothermal behaviour and mould growth risk assessments are simulated with WUFI software. The study shows how emerging construction practices perform poorly with respect to HAM transfer, particularly in hot and humid climatic contexts during the cooling season.Critical configurations are identified and design alternatives suggested so to prevent material damage, guarantee durable wood structures and maintain indoor environment healthiness.
The uptake of buildings employing cross-laminated timber (CLT) assemblies and designed to Passivhaus standard has accelerated internationally over the past two decades due to several factors including responses to the climate crisis by decarbonising the building stock. Structural CLT technology and the Passivhaus certification both show measurable benefits in reducing energy consumption, while contributing to durability and indoor comfort. However, there is a general lack of evidence to support a fast uptake of these technologies in Australia. This paper responds to the compelling need of providing quantitative data and adoption strategies; it explores their combined application as a potential pathway for climate-appropriate design of energy-efficient and durable mass timber envelope solutions for subtropical and tropical Australian climates. Hygrothermal risk assessments of interstitial condensation and mould growth of CLT wall assemblies inform best-practice design of mass timber buildings in hot and humid climates. This research found that the durability of mass timber buildings located in hot and humid climates may benefit from implementing the Passivhaus standard to manage interior conditions. The findings also suggested that climate-specific design of the wall assembly is critical for mass timber buildings, in conjunction with excellent stormwater management practices during construction and corrosion protection for metallic fasteners.
Timber envelopes provide multiple benefits in reducing both operational and embodied energy environmental impacts in construction. However, when poorly designed, they may incur in high risk of mould growth, affecting both building performance and occupant’s wellbeing. This research investigates the risk of mould growth associated with emerging timber envelopes in Australia, particularly looking at mass-timber and timber-framed wall typologies. The study compares the use of two mould growth assessment models: the VTT and the IBP biohygrothermal. Results provide relevant insights on both current design approaches and performance assessment methodologies. Whilst the study is based on Australian practice, conclusions have international relevance and applicability.
