The transition towards a circular economy in the built environment requires robust methodologies to evaluate carbon and material flows at the component level. This paper introduces Carbon Flow Analysis (CFA), an innovative approach that integrates Material Flow Analysis and Life Cycle Assessment to facilitate environmental decision- making for façade renovations. CFA systematically maps embodied carbon and material inputs within façade components, offering a transparent assessment of their circularity potential. The study further refines the selection process through a contextualization framework, which contrasts CFA results against environmental performance ranges derived from Environmental Product Declarations (EPDs) and environmental databanks. Findings demonstrate the variable role of secondary materials in reducing carbon emissions, due to the large variability of impact across materials and components. While CFA provides actionable insights into material selection for façade components, the study highlights the need for standardized circularity indicators and reliable databanks to enhance decision-making in architectural design. By combining quantitative carbon tracking with performance- based contextualization, this research contributes to the development of practical guidelines for achieving carbon-neutral façade renovations.