This paper presents a performance evaluation of two passive cooling strategies, daytime ventilation and night cooling, for a generic ,six -story suburban apartment in beijing and shanghai . The investigation uses a coupled transient simulation approach to model heat transfer and airflow in the apartments. Wind driven ventilation is simulated using computational fluid dynamics (CFD). Occupant thermal comfort is accessed with Fanger's comfort model .The results show that night cooling is superior to daytime ventilation. Night cooling may replace air - conditioning systems for a significant part of the cooling season in Beijing, but with a high condensation risk. For Shanghai, neither of the two passive cooling strategies can be considered successful.