For sustainable buildings to become mainstream they must demonstrate not only improved environmental performance but also financial performance, benefiting both end users and investors. The perceived financial constraints and risks are often major barriers to sustainable design. This paper discusses the application of a new tool that formalizes the traditionally intuitive-based early-stage decision making processes and assesses the potential for creating a financially feasible best-practice sustainable building across a range of environmental, social and economic parameters, using the limited data available at the outset of a project. It considers the total cost of ownership, demonstrating the link between the recurrent and capital costs. A detailed feasibility assessment of those areas where greatest potential for improving environmental and financial performance exists can then be carried out, saving a considerable amount of time, money and effort otherwise spent on looking at all possible strategies for achieving a sustainable outcome. This approach also identifies areas where incorporating environmental strategies might be financially risky, reassuring investors and developers by reducing investment risks. By reducing some of these risks and perceived barriers to sustainable building development, it is hoped that clients and investors will be further encouraged to adopt a more sustainable approach to their building projects.