Circular procurement has been found unsuccessful in two-thirds of the cases. Literature indicates that Systems Thinking (ST) is required to boost the transition to a circular building sector. This study focuses on the Initiation and Definition (I&D) phase of building projects. Currently several barriers impede the incorporation of circular ambitions in this phase, the study aims to develop a set of intervention strategies that can be used by Project managers (PMS) to overcome the barriers. ST is used and its contribution is evaluated. The research question address is “How can systems thinking contribute to the development of intervention strategies for the incorporation of circular ambitions in the initiation and definition phase of a building project?”

This is a Research through Design study, in which a Causal Loop Diagram (CLD) reflecting the process of incorporating circular ambition in the I&D phase is developed as an artifact. This CLD is used to gain insights in the dynamics in this process and to formulate intervention strategies.

The study begins with a search into the current barrier to circularity in the I&D phase making use of semi-structured interviews. It commences with the development of the CLD and formulation of intervention strategies in three sessions with a focus group. These results are discussed in semi-structured interviews with practitioners who were not involved in the focus group.

A total of twenty-six barriers were identified. The most cited barriers are the expected higher investment required for circular approaches; current financial models that are not organized for circularity and predetermined budgets that do not consider circularity. In the developed CLD six (6) themes were identified: certainty, knowledge, innovation, budget, materials, and courage. Based on this model eight intervention strategies were formulated.

Five (5) out of the eight (8) intervention strategies are related to knowledge and knowledge sharing, indicating the importance thereof. Although the initial hypothesis suggested that through ST different intervention strategies would be formulated compared to event-based thinking, the findings showed limited differences between the two. However, ST proofed valuable in improving the understanding of the dynamics and challenges in incorporating circularity by making mental models explicit and facilitating communication. Key insights highlighted the central role of ‘experience’ in improving the incorporation of circularity in the I&D phase. ST can also be used as a discussion tool among practitioners. It will help to explore circularity and surface underlying problems that impede the uptake of circularity.