The Master’s programme Industrial Ecology is jointly organised by Leiden University and Delft University of Technology. The coming decades, the building sector is facing challenges to reduce its impact as one of the major contributors on global problems, like resource depletion, pollution and climate change. The concept of Circular Economy, combined with aspects of Urban Living Labs, can help them to stimulate innovations and to develop businesses. To support the building sector facing those challenges, three circular building cases are analysed in the Dutch building sector. Based on these cases, this thesis proposed the Circular Building Process Facilitation Tool as guidance to initiate the transformation towards a circular building sector. By providing the clients with closed-ended questions, the tool promotes value based decision-making and the creation of a shared language for fulfilling mutual needs with all the stakeholders in order to develop circular buildings.