Variable Air Volume

VAV systems supply air at a variable airflow rate from an air handling unit (AHU). Because VAV systems can meet varying heating and cooling needs of different building zones, these systems are found in many commercial buildings. Unlike most other air distribution systems, VAV systems use flow control to efficiently condition each building zone while maintaining required minimum flow rates.

There are two major classifications of VAV boxes or terminals—pressure dependent and pressure independent.

A VAV box is considered pressure dependent when the flow rate passing through the box varies with the inlet pressure in the supply duct. This form of control is less desirable because the damper in the box is controlled in response to temperature only and can lead to temperature swings and excessive noise.