What is a VAV Heating and Cooling System?

A variable air volume (VAV) system is a heating, ventilating, and/or air conditioning (HVAC) system that can meet the heating and cooling needs of different sections of a building. HVAC systems are commonly included in the mechanical scope of a construction project and are used to regulate the temperature, humidity, and overall condition of the air inside a space. VAV systems are frequently used in commercial buildings because they can better regulate the temperatures in different offices or units.

A VAV system differentiates itself from the common constant air volume (CAV) system. A CAV system supplies a constant airflow at variable temperature. A VAV system supplies variable air flow at a constant temperature from the air handler with minor temperature adjustments using a heating coil in the box (if needed).

Variable Air Volume Components

Most VAV systems are made with a VAV box that contains three main components: an air damper, controller/actuator, and a coil.

Air Damper

Air passes through a VAV box and the controller/actuator adjusts the air damper allowing variable airflow into different zones of the building. The air damper can be completely closed and this reduces energy use for the entire system.


The VAV controller has a built-in actuator and regulates the flow of heated or cooled air into each of the building zones by operating the fan and air damper.


Select VAV systems have additional coils that can heat or cool the air passing through.

Advantages of a VAV System

  • Precise, individual temperature control
  • Reduced compressor wear
  • Lower energy consumption and more efficient than a CAV system
  • Less noise
  • Additional passive dehumidification

Disadvantages of a VAV System

  • The building’s air handler must have a variable speed fan or air pressure can build up within the system forcing the system to expel conditioned air through a relief vent.
  • If the system isn’t calling for heating or cooling, you can get stale air as the air is only moving when heating or cooling is required. This can be overcome with additional programming to make sure fresh air requirements are met.

Reach out to KMC Partners to learn more about VAV systems and their advantages.

VAV Box Illustration
Source: https://blog.veris.com/hvac-series-part-iv-variable-air-volume-vav-box
Source: https://www.comfort.ucdavis.edu/vav-boxes