Abstract: The present invention relates to a dual duct control system for use in an environmental control system. The dual duct control system is preferably utilized in a dual duct VAV box. The control system advantageously receives room temperature values, mixed air flow values, and positions the actuators in response to temperature values and flow values. The dual duct control system preferably executes a shower algorithm implemented in software to position the actuators. The shower algorithm provides a scheme for incrementally adjusting the hot and cold air flow setpoints for the VAV box so the internal environment reaches a comfortable temperature within a minimum amount of time.