Green Building has been a large focus for the construction industry, with Green Star certified commercial buildings becoming the new standard for commercial office buildings. However there has been little focus on the improvement of existing buildings, and many of Australia's capital cities have ageing building stock that is not operating efficiently and contributing to the nation's growing greenhouse gas emissions. Retrofitting existing buildings for energy efficiency is receiving more attention across Australia, with grants and funding to incentivise owners to find energy efficient solutions for buildings. However it is important that optimising performance of these buildings considers the impact on occupants. Australians spend the majority of their day indoors and the quality of the indoor environment can have a major impact on the health and productivity of workers. This paper covers the development of a tool for a project sponsored by the Sustainable Built Environment National Research Centre to assist building stakeholders identify key energy performance issues with their buildings. The tool explores 5 key areas in buildings that influence energy performance: design elements, building management, occupant experience, agreements and culture and indoor environment quality. The paper explains the development of the tool and some surprising results from the first trial on the tenancy for a 28 year old commercial building in the Perth CBD that underwent a Green Star interiors fit-out. (C) 2013 Elsevier Ltd. All rights reserved.