Designing sustainable buildings that are environmentally friendly and cost-effective is crucial for creating sustainable cities. By combining Building Information Modeling (BIM) with the Canadian green building certification system (LEED), designers can easily select the right materials and make important decisions early on in the design process. This integration helps project teams make sustainable choices and earn the necessary certification points. The methodology allows for the automatic calculation of LEED points and costs for green materials, making it easier to design sustainable buildings in 3D. The use of new plug-ins and an external database streamlines the process of selecting sustainable materials. A real case project demonstrates the effectiveness of this model.