Abstract
Green Building Rating Tools (GBRTs) are a critical mechanism for increasing the energy efficiency of existing buildings and mitigating their contribution to climate change. This research analyses both the technical guiding document and the Certification Rate graph of the voluntary green building rating tool for existing buildings: Green Star Performance, across four different tool versions. It answers the research question of how energy efficiency targets and impacts change across the process of tool revision by examining both the specific changes in the submission guidelines document for each version, and the dynamics of total project certification with different versions over time, captured in the Certification Rate graph.
To achieve this, a clear map is created of the difference between a Green Building Rating Tool (GBRT) and a Green Building Rating System (GBRS), as well as their relation to one another. To assist with isolating the complex and holistic phenomenon of energy efficiency in existing buildings, a model is developed from principles in literature and refined for use on Green Star Performance. The Certification Rate Graph for 10 years of Green Star Performance is also constructed.
Green Star Performance’s current version, version 2, is a major update, changing substantially from version 1.2. The research finds that this version, by virtue of a more stringent minimum requirement for energy efficiency in all buildings seeking certification is more supportive of improved energy efficiency in certified green buildings than any previous version. This is despite the total points-share from the discretionary credits associated with energy efficiency target and impacts being reduced by 23% from the previous version.
It also concludes that the overall trend of an increasing number of projects certified with this tool over time is not reversed at any stage by a change in tool version. Further it finds a general annual pattern in numbers of certifications that is constant over different tool versions. Finally, it maps a lag period between the first certification with a new tool version and the general uptake of that tool version by large numbers of projects of between 1 and 4 years, with an average of 3 years.
These findings and the methodology developed to generate them provide value both to researchers of Green Building Rating Tools (GBRTs), and the custodians and implementers of those tools. They address the shortcomings of some existing methods of GBRT analysis and propose different ways of creating a more complex, more pragmatic, and ultimately a more assistive picture of energy efficiency in existing buildings, and how it can be improved and supported through GBRT revision.