Terminal boxes maintain room temperature by modulating Supply air temperature and airflow in building heating, ventilation and air-conditioning (HVAC) systems. Terminal boxes with conventional control sequences often supply inadequate airflow to a conditioned space, resulting in occupant discomfort, or provide excessive airflow that wastes significant reheat energy. In this study, the procedure for the optimal minimum airflow setpoint was developed to improve thermal comfort and reduce energy consumption. The determined minimum airflow setpoint was applied in all office building air-conditioning system. Improvements in indoor thermal comfort and energy reduction were verified through measurement. The results Show that the minimum airflow, reset can stably maintain room temperature, satisfy comfort standards and reduce energy consumption compared with the conventional control. Copyright (C) 2009 John Wiley & Sons, Ltd.