This technical deep-dive presents the innovation BIM for Circular Value Flow Planning (BIM-CVFP) through the demonstration case “Flat glass to flat glass,”conducted within the REINCARNATE project. The objective is to enable high-quality circular material flows in the construction sector by integrating physical recycling processes with structured, traceable data flows. The demonstration follows windows from a real building scheduled for demolition, documenting their dismantling, transport, pre-treatment, quality assurance, and conversion into cullet for manufacturing new flat glass products. A central focus is the use of inventory data, enterprise system information, and weight measurements to verify material quantities and traceability across the value chain. Results show that approximately 91% of recovered glass could be recycled into new flat glass, demonstrating significant environmental and resource-efficiency potential. The case also evaluates the accuracy of different inventory methods and highlights the importance of standardized data collection and interoperability for circular planning. Overall, the demonstration provides a replicable, data-driven model that addresses key barriers to circular construction: fragmented information, lack of traceability, and limited decision support, while illustrating the practical feasibility of closed-loop recycling for flat glass.