Cool roofs : a climate change mitigation and adaptation strategy for residential buildings

Cool roofs offer a passive solution to reduce cooling demand in buildings. However, they increase heating demand in cold seasons. The annual energy-saving potential of cool roofs greatly depends on climate characteristics and may change over time due to global warming. This is particularly important for cool and mild temperate climates, in which the cool roofs' cooling benefits may exceed their heating penalties in the future. To understand the impact of cool roofs on building energy demand for each climate and to explore their future energy-saving potential, these roofs should be evaluated under both present and future climates. Accordingly, this study aims to: 1) quantify the energy savings (or energy penalties) of cool roofs under a wide range of present climate conditions (from cool to hot climates); 2) evaluate cool roofs' energy-savings potential under future climates; and 3) predict when (and under which climate change scenarios) cool roofs will improve buildings' thermal performance in the future for cool or mild temperate climates. Results showed that cool roofs reduce annual energy loads by up to 14% and 22% in tropical and subtropical climates under present and future climates, respectively. For cool and mild temperate climates, while cool roofs increase the building's total energy demand under present climates, it is predicted that they offer energy-savings in the 2050s and 2070s for Canberra and Melbourne, respectively. Understanding the present and future impacts of cool roofs is essential for the implementation of appropriate climate change mitigation and adaptation strategies for residential buildings in each climate.