Australia's Thermal Housing Challenges
Australia has experienced increased temperatures and more frequent and prolonged heatwaves. The performance of existing housing stock, particularly older constructions, may not be optimally designed for these thermal conditions. Temperatures in Australia's interior can exceed 40°C during heatwaves, posing health risks to residents. Heatwaves have been identified as a significant cause of death in Australia relative to other natural disasters.
Role of Smart Materials
Smart materials, which exhibit controlled property changes in response to external stimuli such as temperature, are being integrated into building components like bricks and roof cladding. This aims to enhance the thermal resilience of homes against temperature fluctuations.
Limitations of Conventional Cooling
Reliance on air conditioning as a primary cooling method presents energy consumption challenges. Increased air conditioning use contributes to higher energy consumption and carbon dioxide emissions when non-renewable energy sources are utilized. Buildings account for approximately 40% of global energy use and nearly one-third of global carbon dioxide emissions. In Australia, heating and cooling can represent up to 50% of household energy consumption, with peak demand occurring during heatwaves. Achieving net-zero emissions targets necessitates alternative approaches to building thermal management, such as the adoption of smart materials.
Phase Change Materials (PCMs)
Phase change materials (PCMs) are a type of smart material designed to passively absorb and release heat. These materials, composed of substances such as waxes, salts, fatty acids, and plant-based oils, are available in various forms, including thin panels, microcapsules, and liquid-filled pouches.
PCMs store latent heat during phase transitions (melting and solidification). In warmer conditions, PCMs absorb heat as they melt, contributing to cooler indoor spaces. When ambient temperatures decrease, they release the stored heat as they solidify. This process can reduce average building energy use by approximately 37% across various Australian urban environments. A limitation of PCMs is their reduced effectiveness during prolonged periods of high overnight temperatures, where they may remain in a melted state and cease absorbing heat.
Reflective Coatings
Reflective coatings applied to rooftops can reduce indoor temperatures by up to 4°C, potentially lowering air conditioning reliance and energy costs. However, these coatings may reduce desired heat absorption during colder months, potentially leading to increased heating needs.
Integrated Adaptive Solutions
Integrating multiple thermal management strategies, such as combining reflective roof coatings with phase change materials (PCMs) embedded in roof tiles and gypsum board, has been studied for enhancing home performance. Research indicates that this combined approach can reduce indoor temperatures by 7.9–9.7 °C and yield energy savings of up to 80.6% during simulated Australian heatwaves, while also improving indoor comfort.
These adaptive roofing systems are projected to become more prevalent in new construction and retrofitting projects within the next decade, driven by intensifying heatwaves and increasing demand for energy efficiency.