Currently, various studies have demonstrated some doubt about the accuracy of the orifice equation when applied to the calculation of cross-ventilation. As a result, a computational fluid dynamic (CFD) simulation is considered the best method of analyzing cross-ventilation properties under present conditions. However, repetition of CFD analysis to determine the optimum ventilation performance is particularly complex. Accordingly, a flow network model that corresponds to cross-ventilation was developed and suggested as a more efficient means of determining the optimal opening conditions. At least one instance of CFD analysis using a model with openings is necessary to investigate the airflow property around a building. The suggested flow network model was established by utilizing the results of the CFD analysis, and relaxing the total pressure loss coefficients.