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 is worth 2.2 MWh of heating and 0.9 of electricity on London's year at its 62.1-derived floors. 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 under ＋ Open include a machine of this kind, and a building tab runs it against a year of weather.

Other terms

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 · Superheat · Subcooling · Sensible heat ratio (SHR) · Bypass factor · Wet-bulb temperature · Dew point · COP and EER · Compressor map · Evaporating and condensing temperature · Range and approach · Heat-recovery (three-pipe) VRF · Typical meteorological year (TMY)