Heat Waves, Heat Stress, and underperforming apartments

Everyone has the right to live well, in safety and comfort; however, many existing apartment buildings are ill-equipped to deal with the uncertainty of climate change and the increase in weather extremes

People in homes without heating and cooling systems in place are at higher risk during heatwaves. This was the situation in 2003, when France had their deadly heatwave claiming over 14000 deaths. Post this event, French authorities regulated that all homes need to be comfortable during 5 consecutive hot days in “free running mode” (without heating or cooling).

Thrive Research Hub has evaluated several apartment buildings, including social housing, student accommodation, a heritage building example, and a modern best practice example. We modelled their performance based on the extremes of the Melbourne 2009 heatwavethat began on the 27 January with daytime temperatures over 43°C across 3 days, with night-time minimums of above 25°C These events are likely to increase in frequency with climate change. Using the temperature profile form the 2009 heatwave, the sample apartments were tested against 4 international thermal comfort standards. For example, the British CIBSE guide recommends a maximum temperature of 28°C for living room and 26°C in bedrooms for less 1% of running time.

Our results show that the typical Melbourne apartments all exceeded maximum temperature thresholds based on the modelling conducted for the heat wave conditions. This means that even the modern best practice example will not be able to maintain comfortable temperatures during an extended heatwave. Thermal mass and glazing orientation are the main elements that determine peak temperature during a heat wave. The results also show that thermal mass, is responsible for sustained high internal temperatures during a heat wave, (e.g. overnight) leading to night time discomfort. Finally, cross-flow natural ventilation is significant in reducing temperatures particularly when there has been significant heat build-up during the day.

With respect to a new Australian regulation, the key recommendations are:

• Emphasise thermal mass in the context of ‘cool room’ (a space that can maintain cooler temperatures when the rest of the apartment cannot)
• Enhance ventilation particularly cross flow.
• Introduce additional thermal modelling that is not currently allowed for under the traditional BCA compliance methodologies.

Meanwhile, to improve existing building stock the best options are: ventilation opportunities, insulation of lightweight and heavyweight (externally) wall types, light colour or cool coatings for north and west facing surfaces (e.g. walls) and external shading of windows provide the most cost effective solutions.

For more information please visit the project website or contact our lead Researcher: Mr. Chris Jensen.