Impact of Rating Levels and Climate Zones on the Performance of Energy Star-Rated Office Buildings

Building certification (both green and energy-efficiency ratings) can contribute to reducing the operational energy consumption of buildings. Certification schemes award ordinal rating levels, and energy performance is expected to align with the ordinal levels where performance increases from lower to higher levels. Other factors like climate conditions can distort this ordinal performance expectation. However, limited research has explored energy performance differences between rating levels and how other factors, like climate conditions, could influence them. Therefore, this research aimed to investigate the ordinal energy performance of commercial buildings rated under Australia's Commercial Building Disclosure (CBD) program while considering the impact of climate differences. A total of 2,606 buildings rated under the “whole building energy rating” category was downloaded from the CBD dataset. The results showed that energy performance followed the ordinal star ratings of the CBD program when climate differences were ignored. However, when climate differences are considered, ordinal performance differences between neighbouring rating levels (like 1star–2star, 3star–4star) are insignificant, while ordinal performance differences between distant ratings (like 1star–3star, 2star–4star) are significant. Therefore, targeted upgrade programs focused on retrofitting 1star, 2star and 3star rated building to 4star and above would contribute to reducing energy consumption and enhance the impact of the CBD program.