This paper demonstrates the use of a combined methodology of wind tunnel experiments and CFD simulations to study the potential of using active stack to enhance natural ventilation in residential apartments in Singapore. Wind tunnel experiments were conducted to provide the boundary conditions for the subsequent CFD simulations. The results obtained from the wind tunnel experiments were also compared with that from CFD simulations to study the discrepancy between the two approaches. A total of 32 CFD simulations were conducted taking into consideration the design factors, which include stack sizes and locations, bedroom door operations, external wind effect and stack fan operation. The results were compared to a base case and the key design factors that significantly affect the ventilation performance were identified using factorial design analysis.