Why so many Australian homes are either too hot or too cold

Josh Nicholas
·3-min read

Much of Australia is enduring the coldest start to winter in decades. But chances are the reason you’re cold is not only due to a polar air mass sweeping the country, but because millions of Australian homes aren’t well insulated.

The average Australian home built before 2003 averages just 1.8 stars on a scale from zero to 10 stars under the Nationwide House Energy Rating Scheme (NatHERS). Homes with zero stars provide little to no protection from the outside climate. On the other end of the spectrum, 10-star homes require little-to-no heating or cooling.

Experts estimate more than 70% of Australian homes were built before 2003. The chart below estimates the number of dwellings in each star category based on when they were built.

Australian homes are so poorly insulated that some experts compare them to tents. This makes it more costly to heat and cool our homes and harder to bring down emissions.

It is also increasingly problematic in a changing climate.

“The way we design and construct [homes] is not even suitable for our current climate,” Associated Professor Trivess Moore from RMIT’s School of property, construction and project management says. “So when the climate changes in the future, we will have an even larger gap in performance.”

Minimum insulation requirements were introduced in the 1990s and a national standard was introduced in 2003. This has been ratcheted up over time – newly constructed homes needed a five-star energy rating in 2006, six stars from 2010 and seven stars since May this year.

Research has found that Australia’s energy standards are about 55% worse than comparable countries and climate zones. Many European countries require something similar to an Australian eight-star rating.

Moving up the star ratings is significant – depending on where you live, going from a six star to seven-star home could reduce the amount of energy required for heating or cooling by between 11% and 27%. And the increases are even larger at the bottom end of the scale.

Houses tend to linger around for quite a while; most of us still live in homes that were constructed long before the current standards were in place. And most of the homes that will exist in 2050 have already been built.

Many homes will have been renovated since 2003, but experts say most renovations will still be below the current new housing standards. And the vast, vast majority of new homes are built to just meet the minimum standards required.

There isn’t a comprehensive dataset of energy efficiency of Australia’s housing stock; experts estimate energy efficiency by looking at how many homes are constructed in between changes to the energy efficiency standards. Guardian Australia followed the same methodology in the chart above.

“We don’t have any trustworthy, robust data about our entire housing stock,” says Prof Moore. “Which mean policymakers are developing policy without good evidence. But also individual households don’t have information about what they could or should be doing to improve the quality of their dwellings.”

Notes and methods:

  • Estimated dwelling stock is derived from the 2001, 2006 and 2011 census.

  • Dwelling stock for the years between each census are estimated by averaging the number of dwellings added in the period between the census.

  • The data does not factor in dwelling removals or renovations.

  • Star data since 2016 based on actual Nationwide House Energy Rating Scheme (NatHERS) certifications data from the CSIRO.

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