Meeting 6 Star ratings requirements a state by state challenge

In May 2011, all new homes were required to be built to meet a nationally implemented 6 Star standard energy rating. However, what constitutes a 6 Star rating differs from state to state and this has provoked nationwide challenges.

The Building Thermal Performance Assessment system was introduced by the Building Code of Australia, and is enforced by state governments. According to the Building Commission of Victoria, a home with a 6 Star rating are projected to use 24% less energy for heating and cooling than 5 Star rated homes.

Although the ratings are applied nationally, the requirements for a six star rating are not universal. The system is designed to be flexible, and is “performance based rather than prescriptive”. As the Star rating system is designed to tackle thermal performance, it is site specific – a home’s orientation on a block (whether it faces north, south, east or west) or its surrounding climate can influence the design factors required to meet a 6 Star rating. In the Northern Territory, for example, homes in certain areas require a breezeway for airflow, while homes in colder climates may not.

According to Natalie O’Shea, a designer at building franchise Hotondo Homes: “It’s challenging to design homes on a national level as each state has its own particular standards and differing requirements.”

“One of the biggest things affecting the energy rating of a home which is consistent across the country is the orientation of the block [of land] and the home,” said O’Shea.

“When you have the right design on the right block there are minimal additions that need to be made. The home will naturally stay warmer in winter and cooler in summer.

“Materials are getting better with their thermal qualities, but extra insulation, double glazed windows and wider eaves may be necessary to add in order to achieve the desired energy rating, but they come at an additional cost.”

A popular home design by Hotondo Homes achieved a 6 Star rating for all orientations in Hobart, Melbourne, Canberra, Adelaide and Perth, according to a 2012 report by Sustainability House, contracted by the Department Climate Change and Energy Efficiency.

The home also achieved a 6 Star rating in three orientations in Sydney, two orientations in Brisbane but only a single orientation in Darwin, despite consistent floor plans (pictured below) and building materials.