Space conditions are directly controlled by terminal boxes in variable air volume (VAV) air handling unit (AHU) systems. The terminal box either modulates airflow or adjusts discharge air temperature. Conditioned space will have thermal discomfort by less air circulation if the airflow and discharge air temperature are not suitable. The objective of this study is to estimate an optimal value of the airflow and discharge air temperature, which maintains room thermal comfort. This paper is conducted to determine the optimal room airflow and discharge air temperature and verify the impact of room airflow and discharge air temperature on thermal stratification through CFD (Computational Fluid Dynamics) simulations.