The Circular Economy (CE) in the built environment has gained attention due to the current unsustainable linear model. There are several indicators to measure the transition towards the CE in the built environment, but no consensus has been reached. Based on previous literature, the design decisions during the preliminary stage of the design should consider circularity performance and environmental impact as key indicators. Traditionally, these assessments are performed at the end of the design stage, limiting their use for making design decisions. Hence, there is a need to develop a framework or a tool to perform the assessment during the design stage. In recent years, Building Information Modelling (BIM) has shown its potential in the construction industry. However, there is limited research on its effectiveness to enhance sustainability driven by CE.

The objective of the research was divided into three parts: determine the necessary CE metrics related to product circularity performance and environmental impact during the design stage; develop a framework and a tool to conduct an assessment during the design stage and determine a method to support designers to make design decisions based on the assessment and project requirements.

A framework was proposed to conduct the assessment during the design stage. A prototype in Revit using Dynamo, a visual programming platform, was developed for conducting the assessment. A multi-criteria decision making (MCDM) using the TOPSIS method was performed on the obtained assessment results for the products to make a trade-off between circularity performance and environmental impact and obtain the best alternative product for the design. A case study and workshop validate the proposed framework. The criteria for evaluation include the applicability of the framework, accuracy of the developed tool for the assessment, usability of the tool and its implication to make a balanced design choice and its contribution towards sustainability and circularity consciousness. Based on the implementation of the developed tool and workshop, it was observed that the tool can be applied to real-time projects and had the ability to support designers to make sound decisions based on circularity and sustainability criteria. It had 95 - 100% accuracy when compared to other commercial tools. During the workshop, it was perceived that over the period of time the developed tool improves the designer's consciousness on circularity and sustainability.