There's a lot of waste involved with VAV systems commonly used in office and commercial buildings. Typically, VAV systems operate with roof-top units (RTUs) in cool-only mode. The supply air temperature is held constant at 55°F and, when a zone falls below its setpoint, the damper closes and reheat is enabled. When a zone is above its setpoint, the damper opens fully to allow as much 55°F air as possible into the zone to cool the space quickly. This cycle often involves first cooling and then heating the same air. Since the RTU operates in cool-only mode, the 55°F air must again be reheated before it is discharged back into the space to keep the zone's air temperature in balance.
See the waste?