Are Australian homes built for the extreme cold?

Are Australian homes built for the extreme cold?

Most of south-eastern Australia is experiencing one of the coldest starts to winter in decades with maximum temperatures in several cities staying below 15°C since the beginning of June. With many Australians cranking up their thermostats, there has been a corresponding increase in power demand, leading to an energy supply crisis.

So are Australian homes built to withstand extreme cold? Not exactly! Adrian Barnett, Associate Professor of Public Health, Queensland University of Technology famously described Australian homes as ‘glorified tents’ when discussing why more Australians died of the cold rather than the heat that the country is known for.

“Perhaps the poor insulation of our cooler climate homes is the result of being on a continent dominated by warm weather, where airflow and big windows make sense,” says Dr Chris Jensen, a lecturer in Construction Management at the Melbourne School of Design, Faculty of Architecture, Building and Planning, University of Melbourne.

Australia was pretty late to the regulatory game when it came to designing and building energy efficient homes. The Nationwide House Energy Rating Scheme, otherwise known as NatHERS, which measures a home’s energy efficiency, was first introduced in 1993 and adopted across the country in 2003. Homes and apartments are assessed and rated from 0 to 10 stars based on the energy performance, where a 0-star rating means the building shell does practically nothing to offer protection against heat or cold, while a 10-star rated home may not need any artificial cooling or heating throughout the year.

Since 2011, new homes across Australia have required a minimum performance of 6 stars to comply with the National Construction Code (NCC) energy efficiency requirements.

However, a research study conducted for the Australian Greenhouse Office in 2005 revealed that Australia’s then minimum standards of 5 stars were actually about 2 stars below the equivalent standards in the UK, US and Canada.

Worse, a significant part of Australia’s housing stock is old – built before the introduction of the minimum energy efficiency requirements. Such homes typically have single glazed windows, leaky building envelopes with poor airtightness, and minimal wall and roof insulation, all of which contribute to reduced energy performance and higher energy bills.

The average Australian home has a rating of 1.8 stars, which means it takes a lot more energy to heat or cool the house when compared to a 6-star or 10-star home. How much more? The annual energy consumption of a 2-star rated 200sqm home in Melbourne would be around $4964 whereas a 6-star home of the same size would see a yearly bill of $1474 and a 10-star home, a mere $26.

High energy costs are also leading to ‘energy poverty’, especially among the vulnerable sections of the Australian population, with one in four households cutting back on their energy use, especially during the hot summers and cold winters. A UNSW study of low-income households in New South Wales, covering 100 social housing units in the Greater Sydney area found that the minimum indoor air temperature was about 5°C during winter (2018) and the maximum indoor air temperature was 39.8°C in summer (2019).

With open plan layouts and large windows to enable flow of fresh air and cross-ventilation, Australian homes are designed to embrace the warm, sunny weather. The same features impact the energy performance of the house during the cold season.

Moreover, 80% of all new homes are designed and built only to the minimum 6-star requirement, which means these buildings cannot deliver the energy performance required to provide thermal comfort to the residents throughout the year.  

So what’s the solution?

For existing homes, especially those built prior to 2003, extensive retrofitting is recommended to prevent heat loss and create an airtight building envelope. Remedies include plugging gaps around windows and doors; sealing ductwork; and installing wall, roof and underfloor insulation. Solutions that would require a significant investment include replacing existing heating and cooling systems with more efficient units; and swapping single glazed windows for double or triple glazed units.

Additionally, raising the minimum energy efficiency requirement from the current 6 stars would ensure that new homes will deliver superior energy performance and year-round thermal comfort to the occupants. However, homeowners need to discuss with their architects and builders about building their homes to deliver higher energy performance rather than accept the minimum mandated requirements.

“Passive design and construction principles work both ways – by making your house better insulated to keep in the heat during winter, you also make it more efficient at keeping cool during summer, especially if efforts are made to better shade windows and other glass areas,” says Dr Jensen.