## 4 Discussion
### Circularity Assessment Frameworks--Scopes and Objectives
For example, a building, e.g., can be made of 100% circular materials and products, but when those are unreachable for replacement or maintenance, the building system becomes non-circular. Multiple sustainability rating tools were used to assess circularity considering it as an added value to sustainability. LCA-based tools such as SimaPro, ReCiPe, and Open LCA are widely used for the sustainability assessment of buildings. The use of LCA tools in the context of circularity assessment considering end-of-life options results in more comprehensive assessments. Yet, these tools only addressed the environmental results without other aspects. Similarly, LCC-based tools are used to address the economic aspect of circularity in buildings, investigate the feasibility of circular solutions and conduct financial impact analysis of circular business models. Still, LCA and LCC methods are considered time-consuming and complex to base design choices on [67]. They also rely in part on inaccessible data. S-LCA or Social Lifecycle Assessment is a relatively recent type of LCA, which has been investigated to complement the triple bottom line of sustainability towards a common framework of sustainability. However, S-LCA has been rarely investigated to calculate the social and socio-economic impacts of products circularity. Furthermore, renowned sustainability certification schemes such as BREEAM and LEED continuously include different aspects of circularity in their assessment models. Although these tools are constantly being upgraded, they are often adapted to marketing purposes and rarely consider the critiques posed by the theoretical and empirical research [70,71]. Moreover, their accessibility and costs are in question for young designers. Some frameworks provide strategies to implement circularity through practical guidelines and successful practices supporting the concept of learning by doing. A prominent example is the circular design guide put forward by the Ellen McArthur Foundation (EMF) and IDEO [72]. Another guide that targets building designers and professionals, in particular, is introduced by VUB Architectural Engineering [73]. This guide illustrates 16 design qualities and principles for a circular economy implementation in buildings. Although useful to establish a circular mindset, these guides do not provide evidence on what circularity measures are the best fit for a certain case. More recent tools have been developed in the spectrum of the CE, such as Circular Building Assessment Prototype (CBA) developed by the European Union (EU) project of BAMB, Circularity Calculator [50], and Building Circularity Index [57]. These tools introduce rating systems to calculate a circularity score aiming at objetiying the circularity performance of a building or a building element. However, they are criticized for their lack of a participatory and practice-oriented approach, which is fundamental to the need to apprise the impact of rating tools on the design process. Moreover, there is no clear link between the outcome of these tools and the actual environmental impact of the investigated solution. The Level(s) framework developed by the European Commission introduced a more inclusive approach towards circularity in this regard. However, the consideration of circularity here is mainly featured in macro-objective 2--resource efficiency and circular material lifecycles--consisting of three lifecycle tools. Although Level(s) provides guidelines for doing simplified, detailed, or optimization studies, it delivers a less concrete framework for circular design strategies such as Dfa, which is assessed relying on simple checklists. Moreover, the market uptake of Level(s) is still limited, and a strong position still has to be found in the playing field of international frameworks such as LEED and BREEAM and other national frameworks. The multiple aspects addressed by the different types of tools and the similarities among most objectives point out the need to create complementarity rather than establish new ones from scratch.