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Modern homes trapping heat 'like a plastic bag'

By Malcolm Sutton, Thursday January 4, 2018 - 17:51 EDT
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Modern, box-like townhouses have been popping up across Australian cities and suburbs. - ABC

In a country where capital city temperatures regularly exceed 35 degrees Celsius and even 40C in some states, it could be expected that modern houses are already built to resist heat.



But some modern housing developments, such as new suburbs established on former rural zones in Adelaide, have included structures with next-to-no eaves positioned gutter-to-gutter with adjacent houses.

In the city's CBD and surrounding suburbs, multi-story box-like designs have popped up with no eaves at all.

Both designs can have a heavy reliance on air conditioning to keep interiors cool, trapping heat "like a plastic bag".

Experts call for change to building code

University of South Australia research associate Gertrud Hatvani-Kovacs has to encourage designs that are heat stress-resistant.



Dr Hatvani-Kovacs said the building code supported energy efficiency but did not "necessarily encourage heat-stress resistance".

"The real concern is, with newly-built buildings that are compliant with the building code, they might get over-insulated and have very high airtightness, but at the same time they lack the natural ventilation and have a lack of shading devices," she said.

"They behave like a plastic bag and do not let the building cool down, so their energy efficiency can be very counterproductive."

She said buildings were rated according to their annual energy consumption and while they may perform very well during winter time and consume much less for heating, their cooling demand was still relatively high.



Most homes — new or old — have 'hidden' sources of heat

ThermoView general manager Sheena Trumble heads an Adelaide company that offers infrared imaging that can discern, among other things, where a house is losing energy.

This can include where a structure is allowing the wrong level of temperature in or out, appliances that are running too hot, or issues with an electricity switchboard.



Ms Trumble said energy efficient buildings that utilised temperature management within their design were "very big in Europe".

"Here in Australia we don't seem as concerned about energy efficiency in houses as they are in parts of Europe, which astounds me because it gets so hot here," she said.

The group recently performed an exercise for Stirling Hospital in the Adelaide Hills as part of an audit to save energy costs.

They found areas of elevated heat in a number of wall sections that indicated possible missing insulation, parts of the building where the sun could be creating more heat, and where thermal bridging (more heat passing between different parts of the building) could increase temperatures.

Ms Trumble said the thermal cameras read surface temperatures within a matter of seconds.



"Insulation is probably one of the biggest [issues]," she said.

"The installers will go in and they'll put it in and somebody will move it at some stage, or they'll have forgotten a bit or missed a bit. We can see that almost instantly."

Based on the group's findings, a building can be retrofitted to overcome temperature abnormalities in a targeted fashion.



Can you keep cool without turning on the air conditioner?

It's possible, according to Dr Hatvani-Kovacs.

"Firstly, locate the south-facing part of the house, which can be cooled down more easily and the temperature maintained, and use it as a cool retreat," she said.

"Always separate the different sections of the house and obviously use the cooler part."

On concrete slab-based floors, she said it was a good idea to roll up rugs and put them away to dissipate heat into the ground as much as possible.

She said the correct use of shade devices and opening windows at night would also help, along with fixing a wet blanket over the open window to cool entering air.

"Obviously the ceiling fan is a wonderful solution, and use evaporative cooling compared to reverse cycle air conditioning," she said.

Dr Hatvani-Kovacs said retrofitting measures could include changing the roof material or paint to be more reflective, better external shading, more options for natural ventilation such as installing fly screens, double glazed windows, and reflective foil with an air gap added to the insulation and into roof cavities.

The ultimate solution, however, is for modern houses to be built with temperature management in mind.

"And in the Adelaide climate, it's definitely useful to have the slab-on-ground structure, instead of having suspended slabs, because this way the thermal mass under the building can be utilised," Dr Hatvani-Kovacs said.

"Using ceramic tiles on the slab can also help."

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- ABC

© ABC 2018

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