Experts give red mark to green home ratings

The [Australian] Federal Government wants all homes for sale or rent to have an energy efficient rating, but experts say the system used to attain that rating is flawed and will result in unhappy homebuyers.

The rating system is supposed to reveal the energy performance of a building - to inform people whether they could face big power bills to heat or cool a home.

Scores are awarded according to the home's energy efficiency. A score of zero means the building does virtually nothing to protect occupants from hot or cold weather. A score of 10 means occupants may not need a heater or cooler at all.

The scheme would be based on an existing rating system, which has been used in the ACT for more than a decade.

New homes in Australia already have to meet a minimum energy efficiency rating, which is now six stars across most states and territories.

But the Government's plan would require homes for sale and rent to also have a rating.

Some states have made it clear they do not want to see the energy rating scheme expanded to older homes. Victoria's Planning Minister Matthew Guy has publicly denounced the idea, calling it "yet another hair-brained tax idea from the Federal Government".

The rating costs about $150 per home in the ACT - the only state or territory that rates older homes.

The ACT has had mandatory disclosure of energy ratings on all homes for more than a decade.

That is because Canberra has Australia's biggest temperature range for a metropolitan centre - reaching 40 degrees Celsius in summer, and falling to -8 degrees last winter.

Winter heating costs are particularly large and make up the bulk of residential power bills.

ACT-based energy ratings assessor Jenny Edwards supports the idea of rating older homes. She says it enables the public to make more informed choices when choosing a home, and it can put pressure on property owners to make homes more energy efficient.

But Ms Edwards says there are often differences between the rating, and how the house actually performs.

When she bought her own home in Canberra's inner-south, it was rated at three stars. On living in it, and with further investigation, Ms Edwards found out it was closer to a one star. "The first winter was freezing and the first summer was sweltering. (It is an) incredibly uncomfortable house to live in," she said.

There are many reasons why a home fails to perform as well as it is rated, including air leaks and patchy insulation.

But the ratings assessment is only a visual check of the obvious features that would affect heating and cooling bills - like orientation, window size and insulation.

Canberra assessors do not use equipment to test for air leakage, or thermal cameras to check for gaps in insulation. "We have to assume," Ms Edwards said. People are certainly finding that they can move into a house and find that it doesn't perform as a star rating might suggest it would.

"We can't take all the lining off the house and check the insulation has been thoroughly and evenly installed or that there are R2 batts and not R1 batts; that there aren't big gaps in the house and assessing for air leakage is not something you can do quickly and superficially."

Ms Edwards says the ratings software used for Canberra's older homes is basic, introduced 12 years ago. And she says there is another problem with the quality of assessment. "The level of training has been questionable. The ease with which you can manipulate the outcome, again whether it has been intentional, accidental - due to lack of training no-one can be sure," she said.

"People are certainly finding that they can move into a house and find that it doesn't perform as a star rating might suggest it would."

Ms Edwards says a national rollout of energy ratings to older homes is not straightforward. "There is a lot of potential for issues. And how we resolve that is complicated," she said.

Public interest in the Canberra system is also lacklustre, according to a leading real estate firm.

Peta Swarbrick from LJ Hooker's city office says energy ratings are not a key concern for her clients.

"The idea is fabulous. It is absolutely a must with the whole notion of energy starting to cost more but ... it is probably the least referred to part of the contract," she said.

"And if you look at it, it looks unimpressive. It's a bunch of numbers and it's got these very sort of black and white quasi-scientific looking table and it doesn't really tell me about my house."

Tone Wheeler, an architect who teaches at the University of New South Wales, says the rating system is imperfect because it is based on science that was never designed to calculate the energy efficiency of houses or star ratings.

Mr Wheeler worked with the CSIRO in the 70s, using the precursor to the computer engine now used to run the software at the heart of the energy ratings system.

He says the computer engine was designed for architectural scientists. "It was designed to measure thermal comfort... the idea of a comfortable temperature in a room," he said.

Mr Wheeler says in the mid-1990s, the NSW government approached CSIRO scientists to expand the scope of their computer engine. The government wanted a way of comparing the energy use of different houses.

So the CSIRO scientists adapted the engine to also calculate the amount of energy it would take to air condition a room to a comfortable temperature.

"Then the scientists were asked to give star ratings for various levels of performance, but based on some very arbitrary criteria," Mr Wheeler said. "I think our politicians assumed that this thing works. I am convinced that we don't have the data to say one way or the other at this stage."


1 comment:

  1. One of the most important factors is where you build the home - will you have access to public transportation or will you need a car? Can you walk to the grocery store and the green market - or will you need to drive?

    Another factor is size smaller homes use less energy - they take less energy to heat and cool and use less materials to build. Multifamily homes are even better.


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