variableairvolume

Variable air volume (VAV) refers to a class of HVAC systems that regulate the amount of conditioned air delivered to different spaces, rather than altering the supply air temperature alone, in order to meet varying cooling and heating loads. By adjusting airflow to individual zones, VAV systems aim to improve comfort and energy efficiency in buildings with diverse occupancy and usage patterns.

In a typical single-duct VAV arrangement, a central air handling unit supplies air at a relatively constant temperature. VAV dampers within each zone’s box open or close to control the volume of air reaching that space based on its thermostat or sensors. When cooling is required, dampers open to increase flow; when cooling demand decreases, dampers close to reduce flow. In some designs, heating is addressed locally through reheat devices in the zone, such as electric or hydronic coils, to fine-tune temperature without altering supply conditions for all zones.

VAV systems come in several configurations. Single-duct VAV is the most common, while dual-duct VAV supplies both hot and cold air separately to each zone. Multizone VAV uses a shared air stream but employs separate dampers and reheat strategies to satisfy multiple zones with different loads. Controls range from pneumatic and electronic to digitally networked systems using building automation protocols.

Benefits of VAV include reduced energy use by matching airflow to demand, improved occupant comfort through zone-level control, and simplified ductwork routing in larger buildings. Limitations can include potential temperature fluctuations in some zones, higher initial complexity, and maintenance requirements for dampers and sensors. Proper design, commissioning, and controls optimization are essential for achieving anticipated performance.