Demand-controlled ventilation (DCV) is a control strategy where equipment responds to the actual “demand” (need) for ventilation in a building zone. It does this by varying the rate at which outdoor air is delivered to that zone. DCV saves energy by avoiding the heating, cooling, and dehumidification of more ventilation air than is needed. Carbon dioxide sensors are the most widely accepted technology currently available for implementing DCV. These sensors may be placed in either the return air ducts of the single zone systems or in the zone themselves.
The DCV strategy should result in the outdoor air damper adjusting in a way that the ventilation rate varies continuously between the minimum ventilation set point and the design ventilation set point of the affected space based on the occupancy at any given time. Time of day schedules may not be used as a means to determine occupancy in the affected space. The operation of the economizer should override the DCV control strategy.