Higher star energy ratings save energy, greenhouse emissions and money

A recent CSIRO study has found houses rated 5 stars and above have significantly decreased running costs and are cheaper to build.

The report, The Evaluation of the 5-Star Energy Efficiency Standard for Residential Buildings, details the results of a study undertaken by CSIRO to evaluate the effectiveness of 5 Star standards for houses.

The study, which sought to find the costs and benefits of placing the 5 Star energy rating standard in the Building Code of Australia in 2006, found that the higher standard significantly reduced the energy needed to keep houses warm in winter.

In higher-rated houses average winter energy use compared to lower-rated houses was 50 per cent less in Melbourne, 19 per cent less in Adelaide and negligible in Brisbane. These houses were also on average 1 degree warmer than lower-rated houses with energy ratings of less than 5.

The report also found that it is cheaper to build a 5 Star or higher-rated house than a lower-rated house. The average savings for the elements of a building related to achieving the higher star rating were $7,500 in Brisbane, $5,500 in Adelaide and $5,000 in Melbourne. This result was mainly due to increases in insulation and a more rectangular floor plan.

Overall greenhouse gas emissions for higher rated houses in all cities were found to be 7% less over the year. This is despite greater summer cooling energy use in these houses in Melbourne and Brisbane and increased greenhouse gas emissions in all higher-rated houses during this season. The report indicates that the increased greenhouse gas emissions during this time could be because the residents of these houses tend to have children and greater daytime occupancy than the lower-rated houses. CSIRO concluded that more research is needed to better understand this result.

CSIRO surveyed 414 volunteer households of different star ratings in Brisbane, Adelaide and Melbourne. The research compared inside and outside temperatures, analysed energy bills and measured the energy used by heating and cooling appliances.

House star energy ratings are a measure of the thermal performance of a home as it is designed. A 10 Star home should need no heating or cooling. Across Australia, new houses have to be built to a minimum of 6 Stars, except in the Northern Territory where the minimum is 5 Stars.

You can download and read the report here >

Image: The Green Swing, WA, © Sebastian Mrugalski

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