The New South Wales Department of Environment, Climate Change and Water ((DECCW) is planning to expand the National Australian Built Environment Rating System (NABERS) that rates an office building's energy efficiency from five star rating scale to six or seven stars.

DECCW Acting Built Environment Manager Mark Davis said: "When the NABERS Energy rating scale was created 10 years ago, we thought five stars was the best any building could be possibly be. It was an aspirational target."

"A decade on, technology and management practices in the property sector have improved greatly, helped by the reliability of NABERS as a measure," he said. "Today, approximately five percent of buildings are achieving five star ratings and some developments are already targeting beyond five stars.

The government agency uses NABERS as an environmental performance benchmarking tool for the countries top cities. After a decade in use, NABERS is recognized as the industry standard in Australia and is regarded as a world leading rating system for building environmental performance. It is a performance-based system that measures a building's impact on the environment.

"There are currently no buildings that would achieve seven stars and perhaps eight around Australia that may reach beyond the existing five," Davis said."One of the issues of concern for industry is that a 7-star benchmark may diminish the significant achievement of today's commendable 4.5 or 5 star rating."