Zonal demand control ventilation for a building

A system for heating, ventilation, and air conditioning associated with first and second thermal zones of an enclosed space having a plurality of zones, the system comprising:

• an air handling unit (AHU) or a rooftop unit (RTU) comprising:
• an outside air flow actuator and a variable air volume (VAV) device associated with the first and second zones wherein each VAV device includes a VAV air flow actuator and a VAV air temperature control actuator;
• a controller configured to operate the outside air flow actuator to enable breathing air flow in a supply duct during a high outdoor air time period wherein the supply duct conveys breathing air to the first and second zones and wherein the first zone includes a first number of occupants and the second zone includes a second number of occupants that is less than the first number of occupants;
• and to enable conditioning air flow into the supply duct during a low outdoor air time period wherein the supply duct conveys conditioning air to the first and second zones;
• the controller further configured to operate the AHU or RTU and VAV air flow actuators to provide a desired amount of breathing air from the supply duct to the first zone suitable for the first number of occupants and breathing air to the second zone suitable for the second number of occupants, wherein the AHU or RTU and VAV air flow actuators are operated during the high and low outdoor air time periods;
• the controller further configured to operate the VAV air temperature control actuator to condition breathing air received from the supply duct to provide conditioning air to the first zone having a suitable temperature for the first number of occupants and conditioning air to the second zone having a temperature suitable for the second number of occupants;
• a carbon dioxide (CO2) sensor in a return air duct of the AHU, wherein the CO2 sensor detects a combined CO2 level generated by the occupants in the first and second zones;
• and
• wherein the controller is configured to calculate a maximum allowable CO2 level for an associated zone based on a combined CO2 level measurement within the return duct for the first and second zones and the number of occupants in the associated zone, and responsive to the detected combined CO2 level, generate a pulse width modulated control signal for the outside air flow actuator, wherein the duty ratio is controlled for minimizing outside air introduction to the supply duct while maintaining a carbon dioxide (CO2) level for each of the first zone and the second zone below the maximum allowable CO2 level.