Sustainability within the built environment is increasingly important to our global community as it minimizes environmental impact whilst providing economic and social benefits. Governments recognize the importance of sustainability by providing economic incentives and tenants, particularly large enterprises seek facilities that align with their corporate social responsibility objectives. Claiming sustainability outcomes clearly has benefits for facility owners and facility occupants that have sustainability as part of their business objectives but there are also incentives to overstate the value delivered or only measure parts of the facility lifecycle that provide attractive results. Whilst there is a plethora of research on Building Information Management (BIM) systems within the construction industry there has been limited research on BIM in the facilities management \& sustainability fields. The significant contribution with this research is the integration of blockchain for the purposes of transaction assurance with development of a working model spanning BIM and blockchain underpinning phase one of this research. From an industry perspective the contribution of this paper is to articulate a path to integrate a wide range of mature and emerging technologies into solutions that deliver trusted results for government, facility owners, tenants and other directly impacted stakeholders to assess the sustainability impact.