Mitigation of heat stress risks through building energy efficiency upgrade: a case study of Melbourne, Australia

People spend most of their time indoor during a heatwave period, as such assessment of indoor heat stress is an important issue for public health care. In this study, the impact of building energy efficiency in mitigating the risks of experiencing heat stress by the occupants different energy-rated dwellings was investigated under the 2009 Melbourne heatwave scenario. First of all, distributions of different energy-rated houses and the percentage of people living in those houses were calculated. Indoor heat stress conditions of the different energy-rated houses were calculated using building simulation software EnergyPlus and two well-established heat stress indices: wet bulb globe temperature and discomfort index. The results showed that residents of 0.9 energy star-rated houses are approximately 50% more vulnerable to experiencing heat stress during a heatwave compared to the residents of 5.4 energy star-rated houses. It was revealed that upgrading energy efficiency of existing dwellings could be one of the most effective heatwave mitigation measures. If the entire lower energy-rated houses can be upgraded to 5.4-star, the percentage of people that are at risk of being exposed to extreme heat stress conditions for 6 h could reduce from 50% to only 4%.