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Stay cool with revised house construction codes

Posted by on February 15th, 2019 · Climate change, Construction, Government, Guest appearance, Housing, Housing conditions, Sustainability, Sydney, Wellbeing

By Professor Mat Santamouris, Built Environment, UNSW Sydney. This article was first published by the Sydney Morning Herald.

For many Australian households, summer’s debilitating heatwaves will be felt well into autumn as the steep costs of airconditioning show up on household power bills. We shouldn’t have to live like this.

Much of the punitive cost of cooling is not down to power prices but to cheap and thoughtless construction and design. What’s most exasperating is we already have the materials, knowledge and skills we need to better protect ourselves from climatic extremes, without boosting electricity demand and costs.

Take, for example, ‘Josh’s House’ in Perth, a zero-carbon home of ABC TV’s Gardening Australia fame. In late January the outdoor temperature was hovering around 40 degrees, inside it was a comfortable 24 degrees. This 10-star energy efficient ‘living laboratory’ was not using airconditioning, so no additional energy was needed. Its excellent thermal performance was simply down to good passive solar design.

By contrast, on hot days in Sydney’s west, electricity demand for cooling doubles and the health, comfort and wellbeing of residents is at risk. Our recent research across this large expanse of Sydney suburbs that lies beyond the reach of moderating coastal breezes, found indoor temperatures of up to 35 degrees in poorly constructed homes.

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.

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