Energy Consumption and Carbon Emissions of Mandatory Green Certified Offices in Australia: Evidence and Lessons Learnt across 2011–2020

With the changing trends in global climate and increasing awareness of the environmental impact of the built environment, private and public sector building stakeholders are under constant and mounting pressure to reduce carbon emissions, energy consumption and waste generation. Conceptually, green building regulations are claimed to be the most effective tool toward promoting better environmental outcomes. Nonetheless, there is limited empirical evidence to justify claims for their effectiveness, especially in the Australian context, despite the introduction of various green building standards and regulations over the past two decades. In addressing this gap, this research aims to map the energy consumption and carbon emissions of certified offices under the mandatory Commercial Building Disclosure program. For this, the energy and carbon efficiencies of green certified commercial offices within the eight Australian central business districts (CBD) for 2011–2020 were assessed, and the offices were classified as green and non-green offices, based on their National Australian Built Environment Rating System (NABERS) of fewer than 4, and 4 and above stars, respectively. Data were extracted from the Commercial Building Disclosure program datasheet and thereafter analysed using various descriptive and inferential statistical techniques. Furthermore, the normalisation process was undertaken to capture the relative changes in energy and environmental performance between green and non-green offices. The results show an encouraging trend of a possible significant improvement in energy savings, and a reduction in carbon emissions for offices that have undergone retrofit and obtained an increase in their NABERS ratings. However, it is notable that 6-star NABERS-certified offices sometimes tend to save less energy than their 4- and 5-star rated counterparts, despite their high initial investment costs. Thus, this informs policymakers, authorities and practitioners that the highest NABERS rating does not necessarily help reduce energy consumption in buildings, and that greater emphasis should be placed on promoting the use of a whole building design approach, by exploring a more effective and appropriate combination of features, systems and materials based on stakeholders’ needs and behaviours.