**Appendix A. Interview Guide**

Face-to-face, semi-structured interviews were conducted to identify the specific needs of building designers and advising engineers who are trying to integrate circular principles in their practice and designs for design support tools (and their features) for circular building. The following questions served as an interview guide:


For example, for the category "Circularity Score", the following questions were asked: According to you, is a tool that measures the degree of circularity in a building useful? What criteria should be used to assess whether a product, component, element or building as a whole is circular or not?
