Free cooling strategies are gaining importance in design practice due to the increased risk of overheating in well-insulated buildings with high internal loads such as offices. The state of the art highlights that the most efficient passive solution for indoor temperature stabilization and control is the integration of thermal mass with an optimized ventilative cooling profile to enhance the thermal cycle of heat storage. Due to its cyclical behavior, thermal mass effects are difficult to predict and quantify with the traditional steady-state approach to building thermal performance. Dynamic thermal simulations help to assess a building’s behavior under transient situations, including the thermal mass influence. However, building codes usually include thermal simulations based on standard assumptions: typical meteorological year (TMY), standard occupancy, standard daily-based lighting and appliances profiles, and standard weekly-based occupancy. Thus, when assumptions change, the actual behavior of the building may vary consistently from the predicted conditions. In this paper, we focused on the ability of thermal mass to contrast the influence of variations from the standard assumptions, especially in relation to climate and ventilation profiles. The results show the necessity of encompassing different risk scenarios when evaluating a free cooling solution performance. Among the different scenarios simulated, natural ventilation misuse shows greater influence on the thermal indoor environment, especially if coupled with low thermal mass.

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.