100% OA System vs baseline systems

I'm working on a model for a system designed for a small classroom building and have concerns on the proper baseline and proposed system ventilation rates. Thanks in advance for any advice or insight. The designed HVAC system is a VAV, 100% Outside Air Unit with an Relief/Outside Air Enthalpy Wheel with HW reheat. The unit includes a recirc damper to allow 100% return air during unoccupied periods, but does not provide for return air during normal operation or direct control of the outside air quantity at any time. The unit has a design airflow of 3,000 cfm and VAV minimum airflow of 800 cfm. My primary concerning is modeling the baseline ventilation rate. The building is non-residential,