Energy efficiency was first mandated for commercial buildings in 2006 in Part J of The Building Code of Australia (BCA) and regulators are already implementing increased measures in 2010 (ABCB 2010). Further increases will follow as part of the co-ordinated effort to reduce building related greenhouse gas emissions. The introduction of the Energy Efficiency Disclosure Bill 2010 will establish a national scheme to promote the disclosure of information about the energy efficiency of office buildings as well as further highlighting the need for efficiency. Increased energy efficiency in the form of insulation, energy efficient light fittings, sophisticated Building Management Systems (BMS), micro-generation such as solar and wind turbines all result in measurable quantifiable reductions in operating costs for owners and tenants. However convincing all building owners about the sound business case for adopting sustainability measures has not been fully realised. To-date the adoption of cutting edge sustainable buildings in Australia is restricted to a few industry leaders, such as Investa and ISPT in Victoria for example. Sustainable building owners and tenants often benefit from reduced operating costs during the building lifecycle although the ‘intangible’ effect on businesses (e.g. employee productivity) is uncertain. This aspect has not been accurately quantified and has not been included as part of the measurement of sustainability in buildings.This study will allow property stakeholders, including government policy-makers and investors/developers, to better understand the optimal type and level of sustainability to be incorporated into the built environment. In addition this knowledge will enable policymakers to make more informed decisions with regards to the likely impact of the legislative measures they propose in respect of sustainability and buildings in The Building Code of Australia (BCA) and other relevant legislation.<br /