In an era when sustainability and climate change mitigation are paramount, it is important that built environment professionals make robust and transparent decisions regarding future development. A new approach is outlined and tested for assessing sustainability for built infrastructure using a quadrant model and 3D spatial coordinates. The chosen method involves a case study of a high performance green building in Australia that was constructed in 2008. The investigation demonstrates that the model is practical and produces an appropriate outcome, which is then compared with seven other generic types of built infrastructure. The inclusion of development scale or influence in the model is an important feature that can lead to differences in ranking preference. The findings support embedding essential environmental considerations objectively into decision-making processes via the use of an economic ratio (return on investment to energy usage), a social ratio (functional performance to loss of habitat) and a measure of sustainability risk as x, y and z coordinates respectively, plotted in 3D space.