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What is the future for star ratings? Jesse Clarke, CSR Building Scientist investigates

The Australian building industry has only had energy efficiency codes and star ratings since 2004 – less than 10 years.  We have already seen them significantly influence building design – both commercial and residential. 

So, where have we been and where are we heading – what do the stars tells us?

In Australia as many as 140,000 new homes are built every year to these energy efficiency standards. To illustrate how far the thermal performance of buildings has come over the decades, we looked at some examples of the likely ratings that would be achieved by homes built in years gone by:


Victoria introduced mandatory insulation for new homes in 1990. In 2005, the Building Code of Australia required new homes to be 3.5 star rated. This was increased to 5 stars in 2007, and further to 6 stars in 2010. CSR estimates for all the homes in Australia, the average star rating would currently be around 2.8.


Energy costs in Australia are now higher than in the USA

Australians have traditionally had low energy costs and high land prices which inevitably places pressure on construction costs and reduces the incentive for energy-efficiency initiatives. 

Balancing energy efficiency, affordability and comfort has become one of the pressing challenges for the whole building industry.

So how can we use building astrology to tell us the future?

Rising energy costs in Australia are fuelling a drive for cost savings in the building industry. By understanding the potential for energy efficiency through calculations using the NatHERS software, we can estimate the energy savings (and dollar savings) of energy-efficiency upgrades with a high degree of precision. 

The greatest potential for finding energy savings at lowest cost is by utilising this method of assessment and analysis at the concept design stage.

Ability to influence energy efficiency against the cost to implement over time

The two key things that determine the star performance of buildings is the amount of heat loss and heat gain. Get the balance right and your building will be comfortable all year round.

The three key ways to balance the heat losses and gains are:

  1. orientation of glazed areas,
  2. the performance properties of the insulation and;
  3. the performance properties of the windows.

Generally, higher performance insulation and higher performance glazing is more expensive than stock standard products, so balancing the heat losses and gains also needs to be weighed up against the cost of controlling heat. 

At CSR we are embarking on the huge industry challenge of improving integration of the sustainability measures included in NatHERS – from design through to the construction stage – delivering maximum cost savings to homeowners.

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