A new report by Green Building Council of Australia (GBCA) shows that modelled energy performance of Green Star certified buildings is being achieved in the operation of buildings, as demonstrated by NABERS Energy ratings.

Key findings of the report include:

• 88.1% of Green Star-rated buildings in the sample achieved their modelled NABERS Energy rating or were within 0.5 stars.
• 75% of Green Star-rated buildings achieved their modelled NABERS rating when operating at Peak Performance.
• 91% of Green Star rated buildings with NABERS Commitment Agreements met or exceeded their NABERS Energy target.

The report drew on new research, funded by the Australian Government Department of Industry, Science, Energy and Resources, into the closing of the building energy performance gap in Australia’s Green Star rated offices. This research was peer-reviewed by Building 4.0 CRC’s Dr Victor Bunster, a CRC Project Leader, and an expert in environmentally sustainable design (ESD) life-cycle assessment (LCA), and energy.

“In my review, I checked that the methodology and assumptions matched the results and conclusions of the study,” Dr Bunster said. “I found the most interesting outcome to be the impact of the NABERS Commitment Agreements on the performance of Green Rated buildings.

“The GBCA report uses NABERS ratings to measure the gap between the predicted and actual performance of Green Rated buildings,” Dr Bunster explained. Interestingly, Dr Bunster notes that “The NABERS rating system focuses on the actual (measured) environmental performance of buildings rather than their design, meaning that the rating process needs the buildings to be constructed. In this context, the Commitment Agreements are contracts signed by the building developer or owner committing to achieve a specific rating.

“The study demonstrates that these Commitment Agreements have a major impact in reducing this gap, which has proven to be a substantial challenge to energy policy and sustainability rating systems,“ he concluded.

Helen Bell, Research Manager at GBCA, expressed her gratitude for Building 4.0 CRC’s ability to provide peer reviewing and expert advice.

“Being part of the Building 4.0 CRC consortium has many useful benefits; in this case, we could approach them to look for a suitable reviewer,” Ms Bell said.

“Dr Bunster’s proficient and detailed review has confirmed that these findings are genuine; that our rating systems really do make a difference. In addition to reviewing the findings, his input also deepened the report, providing an additional and extremely valuable perspective.”

“The GBCA report provides real evidence on the effectiveness of sustainability rating systems,” Dr Bunster added. “It demonstrates that the Green Star and NABERS systems make a strong and precise contribution to reducing the environmental impacts of buildings – which remains a key target for industry, government, and the community.” View the full report, Closing the performance gap in Australia’s commercial office sector, on the GBCA’s website.