Stay cool with revised house construction codes

To put this in context, consider the ‘thermal comfort zone’. That is, the narrow temperature range in which humans can operate productively without being distracted, overwhelmed or suffering physical ill effects. Commercial buildings in Australia, for example, usually stipulate indoor comfort be maintained at between 21 and 24 degrees. So, it is not surprising so many Australians have reported sleeping poorly for months, due to the recent intense heat.

We know Australian houses get too hot for relatively simple reasons. Yet we continue to use black or dark roofs, even though the excess heat this traps is well understood. We skimp on insulation in our walls, roofs and windows and pay the price in discomfort or higher energy bills. We continue to pave the surrounding roads with black asphalt that, likewise, acts as a heat sink, And, in many locations, we forego the cooling benefits of trees, parks and open green space to maximise the numbers of dwellings we can squeeze onto a site.

Working in Parramatta with Sydney Water, we recently assessed the potential of cool, reflective materials, planting trees and vegetation and the use of recycled water in features like spray mists and fountains. We found outdoor temperatures could be reduced by 2.5 degrees and, with further work, by up to 4 degrees. Even a 2.5-degree cut would reduce cooling energy costs by 35 per cent and reduce peak electricity demand by 5 per cent, the equivalent of taking 200,000 cars off the road. These are important and encouraging results.

But there is a limit to what can be done to turn the temperature down outside. We must also urgently modify the codes and regulations that dictate the performance of Australian buildings.

A recent study, Built to Perform, found even modest changes in building regulations could reduce Australian household power bills by $900 a year. Some could come at no additional cost, like choosing a light coloured roof over black. Others — including improved insulation, double-glazed windows, better air tightness, outdoor shading and wider eaves, ceiling fans and more efficient airconditioning, lighting and hot water systems -would cost between about $6800 for an apartment to $14,000 for a free standing house. These upfront costs would be more than offset by savings on power bills, the study, funded by the CRC for Low Carbon Living, found.

The COAG Energy Council this month acknowledged our National Construction Code was ‘not set at an optimal level’ and announced a new ‘trajectory’ towards tighter standards. This is a step in the right direction. But we need to move now. Business as usual presents many risks, particularly the opening of a social divide as temperate extremes intensify — between the haves (aircon) and have-nots.

As the federal election approaches, there will be plenty of political finger-pointing over power prices. But we need a more sophisticated debate. Our buildings use 20 per cent of our energy and rapid growth in airconditioning as temperatures rise is a major contributor to peak power demand. We have a major opportunity in better buildings. We need politicians and industries to seize it now.

Professor Mat Santamouris is a researcher in the national Co-operative Research Centre for Low Carbon Living (CRCLCL) and the Anita Lawrence chair in High Performance Architecture at UNSW.




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