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| CSIRO | SOLVE | Issue 6 Feb 06 | |
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ARTICLE
BUILDING DESIGN:
Working Out With the Stars By Jason Major
New software is helping building designers achieve five-star standards for energy efficiency. As Australia grapples with reducing its greenhouse gas emissions, new software is helping building designers meet tough new national building standards that require new homes to reach a five-star standard for energy efficiency. The star rating is based on the sum of a home’s annual heating and cooling requirements; more stars mean it is more comfortable and energy-efficient. Some Australian states are already using software to help implement existing energy-efficiency laws, but the software tools have limitations and have been the subject of controversy.
“AccuRate will play a key role in future building regulation and affect the design and construction of Australian homes,” says the leader of the software’s development team, Dr Angelo Delsante of the Future Cities research theme of CSIRO Manufacturing and Infrastructure Technology. NatHERS, BERS and FirstRate are the software tools used today to calculate a building’s energy efficiency. AccuRate is a greatly improved version of NatHERS and will replace it when it becomes commercially available early this year. The soon-to-be-upgraded versions of BERS and FirstRate will run the calculation engine that powers AccuRate. Overseeing this push for greener homes is the Australian Building Codes Board, the national regulatory body for the building industry, and the Nationwide House Energy Rating Scheme (NatHERS – the same as the software). The scheme is a collaborative one between the Australian Government and state and territory governments, and is managed by the Australian Greenhouse Office. Two of AccuRate’s important improvements are its modelling of natural ventilation and its incorporation of extra climatic zones – in fact all 69 for which the Bureau of Meteorology has sufficient weather data. Natural ventilation is a vital strategy for reducing use of air conditioners. Good ventilation flushes heat from a building and provides cooling air movement. For example, an indoor air speed of one metre per second can have a cooling effect of 3.8ºC. The improved natural ventilation model rewards good design practice in hot and humid climates. Australian building codes have efficiency standards based on just eight climatic zones. With weather data from 69 locations, AccuRate will be able to home in on specific towns or locations, making this aspect of its calculations highly responsive to the local climate. AccuRate can also model up to 50 living spaces within a home. The NatHERS software can model only four. AccuRate was tested using the International Energy Agency BESTEST protocol, a powerful tool for revealing program bugs or deficiencies. “AccuRate compared well against BESTEST’s eight reference programs from Europe and the US,” says Dr Delsante. Just to ensure all bugs were eliminated from the system, hundreds of building designers and builders around Australia, including members of Master Builders Australia, the Royal Australian Institute of Architects and the Building Designers Association of Australia, participated in a real-world trial of AccuRate. Bernard Hockings, from the Association of Building Sustainability Assessors, who managed the trial, says: “To be able to improve the design and construction of a building you need to analyse, measure and compare options. AccuRate is giving us a high level of accuracy and sophistication.” Victoria was the first state to introduce a mandatory five-star rating for all new homes. Sustainability Victoria has commissioned a number of studies into the cost-benefit of five-star homes. One study calculates such homes will save $30–40 million in energy bills, or about $210 per household a year, and boost the economy by having more money invested directly into homes, for example through the purchase of insulation and improved glazing. Most of these products are made in Australia, which directly benefits the Australian economy and helps increase employment. A second study says that within five years five-star homes will reduce greenhouse gas emissions by 200,000 tonnes a year, the equivalent of taking 45,000 cars off the road. And for those worried about the extra cost of a five-star home, a Building Commission Victoria analysis says that for the average 250 square-metre Victorian home, achieving a five-star energy rating adds just 0.6 per cent to the cost of the new house. APPLICATION AccuRate, a new CSIRO-developed software tool, is helping building designers meet tough new national building standards For further information contact: |
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CSIRO has developed AccuRate – software that more precisely assesses the heating and cooling energy-efficiency of even complex building designs and overcomes many of the limitations of the software in use now.
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