Demand-controlled ventilation. The outside-air minimum following how full the rooms are, down to the per-area share and no further. Economiser and outside air.
Ventilation rates in ASHRAE 62.1 have two parts: a per-person rate and a per-area rate. Demand-controlled ventilation lets the outside-air damper's minimum position follow how full the space is — a CO₂ sensor in practice, an occupancy fraction in a model — so an auditorium at a tenth of its seats is not ventilated for a full house. 90.1 §6.4.3.9 requires it in dense spaces above a size.
The floor is the per-area share and the damper never closes below it. Outside air the machine does not have to condition is capacity it can spend on the rooms: on the example mall DCV was worth 6.5 MWh of heating and 5.6 of electricity a year at its 62.1-derived floors, and cut unmet hours by two thirds. In HVAC Builder the base fraction is a property of the rooms' use, computed from Table 6.2.2.1 over what each machine serves.
Open the builder — the examples in the Design tab's sources list include a machine of this kind, and the Simulate tab runs it against a year of weather.
DOAS — dedicated outside-air system · SZVAV — single-zone variable air volume · VAV terminal box · Economiser · Waterside economiser · Face-and-bypass · Head-pressure control · Humidity ceiling and floor · Cycling and modulation · Coupling · Priority · Category · Nested system · Design point and TMY year