The built environment contributes 40% of total global greenhouse gas emissions and 87% of the buildings we will have in 2050 are already built. If predicted climate changes are correct, we need to adapt existing stock sustainably. Outside Australia there is a history of office to residential conversions. These conversions number few in Sydney although evidence suggests a trend is emerging in conversion adaptations. In 2014, 102 000 m2 of office space was earmarked for residential conversion in Sydney as demand for central residential property grows and low interest rates create good conditions. The Central Business District (CBD) population is projected to increase by 4% to 2031 requiring 45 000 new homes and this coincides with a stock of ageing offices. Furthermore, the Sydney office market is set to be flooded with the Barangaroo development supply in 2017; thus conditions for conversion are better than ever. However, what is the level of sustainability in these projects? And, are stakeholders cognisant of sustainability in these projects? Moreover, is a voluntary a mandatory approach going to deliver more sustainability in this market? Through a series of interviews with key stakeholders, this paper investigates the nature and extent of the phenomena in Sydney, as well as the political, economic, social, environmental and technological drivers and barriers to conversion. No major study exists on conversion adaptation in Sydney and the most residential development is new build. There is substantial potential to change the nature of the CBD and enhance sustainability with the residential conversion of office space. The findings show that opportunities are being overlooked to appreciate and acknowledge the sustainability of this type of adaptation and that there is a need for a rating tool to encourage greater levels of sustainability and to acknowledge existing levels of sustainability achieved in these projects.