Green payoff

Houses are being designed for low energy use, but are they worth the extra cost?



AN ENVIRONMENTALLY friendly home has many advantages, including lower power and maintenance bills, healthier atmosphere, superior levels of comfort and helping the environment. But it does cost more to build green. And since most of us live in older houses, what can we do to make them more energy efficient, particularly with power bills rising fast (see panel below)?

The energy efficiency of homes is measured by a star rating. In Australia, new homes have to be built to a six-star energy performance rating. The exception is NSW, where a different standard prevails, and it is closer to five and a bit stars, says Ray Thompson, general manager innovation with building products manufacturer CSR.

A six-star home uses around 70% less heating and cooling energy than the average one-star home. And since heating and cooling energy contributes around 40% to the overall energy use in a home, this adds up to big savings.

Many houses built before 1990 are rated one star. The average star rating of existing Australian homes is about 2.8 stars.

We are now seeing some examples of eight-star homes, which require 50% less heating and cooling energy than a six-star home and 85% less than a one-star dwelling.

An example is CSR House built at Schofields, 45 kilometres west of Sydney. Opened late last year the 250sqm home was designed to cater for conventional buyers but uses about 75% less energy than similar houses built a decade ago. It cost about $325,000 to build, says CSR’s Thompson – about $25,000 more than a comparably sized six-star home.

“We are working on reducing this difference,” he says. “Research is under way now and we aim to drop the cost by about $10,000 or so.”

Proper orientation of the home, window type and placement as well as eave shading to take advantage of the northern sun in winter and limit it in summer are some of the energy-efficient design principles used.

Insulation, draught proofing, effective ventilation to control internal temperatures and air quality and the use of high thermal mass building materials are others. The home also uses solar power delivered through Monier tiles, which have solar panels embedded in them.

Thompson says while the home will deliver significant cost savings in energy bills, it will take many years to recoup the extra cost. “It’s not a straight return on money,” he says. “The home has more insulation, energy-efficient glazing and ventilation which greatly improves the comfort level of the home, so it’s not just about dollar savings.”

There are also capital savings on items such as air-conditioning, which can almost be eliminated, Thompson says.

It’s also a healthier house because it has better air quality and thermal stability. Maintenance costs should also be lower as the home is very well finished, he says.

In Victoria, Cape Paterson Ecovillage is being developed in Bass Coast, about two hours south-east of Melbourne.

Each of the 220 new homes must be orientated for passive solar gain and have a minimum energy rating of 7.5 stars, as well as efficient appliances, at least 2.5 kilowatts of solar energy and 10,000 litres of tank capacity for rainwater.

Buyers can select from 10 house designs, which cost from about $295,000 to build, or use their own plans, as long as they stick to the standards. Based on a study undertaken of the scheme the developer has made some financial predictions of savings residents of the ecovillage may enjoy. The Zero Carbon Study, prepared for developer Cape Paterson Partnership, found that compared with staying in an existing Victorian home – modelled to have four-star building fabric – or buying a new 250sqm six-star home, a 200sqm Cape Paterson home is a significant cost saver.

“The value of future energy and water savings is equivalent to having $58,000 compared to an existing home, or $70,000 for a new home, including build cost reductions, in the bank today,” says the study.

The modelling is based on relatively bullish assumptions about rising energy and water costs. For the savings outlined above to occur, energy costs are predicted to rise 9% a year in the first five years, 6% a year in the subsequent five years and 3% a year in the remaining 10 years. And water is predicted to rise 20% a year in the first five years, 10% a year for the next five and 7% a year for the remaining 10 years.

Brendon Condon, Cape Paterson Ecovillage director, has been quoted as saying that eight years ago when the project was conceived, he thought he would have to offer incentives to help buyers pay the extra upfront costs, but the steep rise in utility bills over the past few years and expected further rises mean this is no longer necessary.

Last year the Housing Industry Association’s GreenSmart home of the year was taken out by the Net Zero Emission home built by Clarendon Homes in conjunction with Landcom at The Ponds, about 40km north-west of Sydney.

It has an eight-star thermal performance rating. When it is built with all the eco options and the net zero facade it would cost $300,650, according to a spokeswoman for Clarendon.

Of course, the trade-off is significantly lower energy bills. There is no comparison cost because Clarendon does not produce any other home as small as this in its designer range.

“The house has been designed so that it has virtually no bills for electricity or water because costs have been controlled by the design and the materials used in construction,” the judges of the GreenSmart award said.

The compact two-bedroom, one-bathroom home is a design and technology leader – comfortable and healthy too. GreenSmart, established by HIA in 1999 to promote affordable and durable environmental solutions for residential design and construction, has an accreditation program for builders.


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