Infiltration accounts for a significant part of heat loss in winter, leading to the need to minimize uncontrolled airflow. Infiltration and ventilation are responsible for 30~40% of energy consumption in air conditioning in building. Improvement of window air permeability is important for saving heat loss through windows. In this study, infilatration air flow rates of a multi-zone officetel are calculated using CONTAM 3.0.1, a simulation program developed by NIST. The results show that wind magnitude, direction, and window permeability are important factors that affect infiltration flow rates.