Face-and-bypass. A damper that sends part of the air across the coil and mixes the rest back; the coil dries the share it sees and the bypassed air is the reheat, for nothing. Humidity: ceilings and floors and the cleanroom case.
A cooling coil dehumidifies by cooling air to its dew point; to hold a room's humidity without over-cooling it, the air must be warmed again afterwards. Face-and-bypass does that without a heater: a damper sends part of the air across the coil face and the rest around it, and the two streams mix back to the supply temperature the room needs. The bypassed air is warm and dry enough; the coil air is cold and dry; the mix lands on both targets.
It is the arrangement a cleanroom or a museum handler has, because the reheat is free. In a building simulation a splitter ahead of a cooling coil and a bypass-role mixing box behind it are recognised as one damper, and a humidity ceiling on the room is held by bisecting the share of air over the coil — the heater stays off. On the example cleanroom it took the reheat from some 300 MWh a year to none.
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 · Demand-controlled ventilation · Head-pressure control · Humidity ceiling and floor · Cycling and modulation · Coupling · Priority · Category · Nested system · Design point and TMY year