## 4 Discussion
### DfA Role in Circularity Frameworks  
Generally, the role of design has been recognized by existing circularity assessment models for buildings where DfA has been identified as a key criterion for circularity and, consequently, sustainability. This can be found in the examples of categories addressed in Sections 3.2.2, 3.2.3 and 3.2.5. However, DfA has been dealt with in different manners. The CE meter [54] introduces a conceptual framework for circularity assessment in buildings where DfA is the core component. The authors consider that circularity criteria should be based on the DfA criteria provided by a previous model developed by the authors to assess the adaptability of buildings (FLEX 2.0 Light). Although the DfA principles were discussed by [PERSON] [55] to create the BCI, aspects of life expectancy and duration were not considered as much as aspects of multiple-life products. The calculation of the BCI helps determine the level of circularity. However, it does not aid in comparing design alternatives. [PERSON] et al. [40] recognize functional adaptability as one of four primary design criteria for increased circularity. C-Calc [74] evaluates three aspects equally weighted in all projects: material use, adaptability, and information flow. The adaptability in this model relies on a building's passive capacity to change its use, limiting the scale of intervention and minimizing engagement of extra resources and energy. The adaptive capacity relies on the reversibility of the component which allows safe recovery of materials with minimal damage. Transformation capacity and functional adaptability are not considered as much. Another aspect about this tool is the emphasis on information tracking during the project's full lifecycle, which is important to establish a closed-loop feedback system ensuring more efficient end-of-life options; i.e., future adaptability, disassembly, and components recovery.  
As for sustainability rating systems such as BREEAM and LEED, aspects related to buildings' adaptive capacity are considered a consequence of integrating the circular economy perspective into these schemes. However, these tools are developed for commercial purposes and certifications, limiting their adequacy for comparison design alternatives. The European common framework Level(s) provide a promising method with an integrated approach accessible for all. The use of the DfA lifecycle tool can be carried out at three levels of performance assessment: common, comparative, and optimized. The common level provides a simple checklist of design aspects that facilitate a building's adaptability. Two forms of the checklist are available for office and residential buildings. The comparative performance assessment relies on using a pre-existing index or assessment tool to deliver a numerical score. In this regard, the Level(s) framework provides some guidance and recommendations regarding the tool to be utilized for the assessment. The optimization assessment includes more complex modeling and consideration of various factors to ensure comprehensive reporting on the improvement potential of the considered adaptability measures. At this level, the framework recommends using a simulation software tool to analyze adaptability scenarios. Given all, the framework is not self-sufficient in terms of adaptability. The reliance on external models brings up questions of compatibility with the scope and objectives of the framework. Since the framework is still under development, future research may address this question together with others related to possible trade-offs among the three lifecycle scenarios and the utilization of BIM tools.  
An overall shortcoming of the frameworks reviewed in this study is that they have not addressed the magnitude of Dfa's impact on the overall building circularity rates. They also fail to compile and embed Dfa principles altogether into the four hierarchal levels of a building composition, i.e., materials, products, systems, and building design.