The Building and Construction Authority Green Mark Certification Standard for New Building (hereinafter BCA Green Mark), a green building rating system established in Singapore, stresses the utilization of CFD analysis to assess natural ventilation. This paper discusses the development of an automated CFD system for CFD users to perform the required analysis with the help of BIM technology and a BIM compatible CFD tool. As a result, the automation enables easy operation and a less time-consuming process. The system also signifies the potential to be applied to other standards.