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Stay cool with revised house construction codes

Posted 13 February 2019 - 12:26pm

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

All the political finger-pointing over rising electricity prices, the energy mix and the adequacy or otherwise of our power grids is distracting us from major opportunity to simultaneously cut household power bills and reduce Australia’s carbon footprint.

Much of the punitive cost of cooling is due to cheap and thoughtless construction and design. Consider, the alternative. For example, in Perth in late January the outdoor temperature was hovering around 40 C°. Inside ‘Josh’s House’, a zero emissions home of ABC TV’s ‘Gardening Australia fame’, it was a comfortable 24 degrees. This 10-star energy efficient ‘living laboratory’ was not using air conditioning, 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 temperatures are between 6 -10°C higher than in the CBD, electricity demand for cooling doubles and the health, comfort and wellbeing of residents is at risk. The large expanse of Sydney suburbs that lie beyond the reach of moderating coastal breezes suffered unprecedented average maximums of over 35 C° last month and even hotter conditions are forecast as the climate changes.

Our recent research in Sydney’s west found indoor temperatures of up to 35 degrees in poorly constructed homes, falling to between 6  and10°C in winter. To put that in context, compare it to what we call the ‘thermal comfort zone’. That’s the narrow temperature range in which we can operate productively without being distracted, overwhelmed or suffering physical ill effects. Commercial buildings in Australia, for example, usually stipulate indoor temperatures are maintained at between 21 and 24 C°. So, it is not surprising that so many Australians have reported sleeping poorly for months, due to the recent heat.

What is exasperating is that we have a comprehensive body of research in Australia, and worldwide, that could, and should, be informing new urban development – and the retrofitting of existing homes. We can better protect ourselves from climatic extremes, without boosting electricity demand and costs.

We know our houses get too hot for many relatively simple reasons. 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 three outdoor urban cooling strategies; the use of cool, reflective materials, planting trees and vegetation and the use of recycled water in features like spray mists and fountains. Our calculations suggest outdoor temperatures can be reduced by 2.5 degrees C and, with further work, by up to 4 C°. Even a 2.5 C° reduction would reduce cooling energy costs by 35% and reduce peak electricity demand by 5%, the equivalent of taking about 200,000 cars off the road. These are important and encouraging results.

However, there is a limit to what can be done to turn the temperature down outside. We must also urgently adapt the codes and regulations that dictate the performance of Australian buildings. Worldwide, the improved thermal performance of buildings is already demonstrating the benefits.

The CRC for Low Carbon Living-funded Australian study, Built to Perform, produced by the Australian Sustainable Built Environment Council, 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 air conditioning, lighting and hot water systems, would cost between about $6,800 for an apartment to $14,000 for a free standing house. These upfront costs would be more than offset by savings on power bills.

To date, Australia has largely left the building industry to regulate itself. However, the COAG Energy Council this month acknowledged the current National Construction Code is ‘not set at an optimal level’ to tackle market failure 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 present many risks, particularly the opening up of a new social divide as temperate extremes intensify - between the haves (air con) and have-nots.

As the Federal election approaches, there will be numerous promises on the table in the ferocious competition to convince voters that one party or the another can rein in power prices. We need a more sophisticated debate. Our buildings use 20% of our energy and rapid growth in air conditioning as temperatures rise is a major contributor to peak power demand, as well as grid failures.

We have the materials, knowledge and skills to make both immediate and future improvements. We now need our politicians and industries to seize this opportunity.

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.

An edited version of this comment piece was originally published in the Sydney Morning Herald