What is a variable air volume (VAV) system?

A variable air volume (VAV) system is an HVAC system that allows for varying airflow based on demand. This type of system is designed to adjust the volume of air that is supplied to different areas of a building according to the specific heating or cooling requirements of those spaces at any given time.

The VAV system does this by using variable-speed fans and dampers that change the flow of conditioned air in response to real-time temperature readings and occupancy levels. As a result, when a room needs more heating or cooling, the system increases the airflow, and when less is required, the airflow is reduced. This capability leads to improved energy efficiency, as the system operates only as much as necessary to maintain comfort levels.

In contrast, the other options reference systems with fixed parameters or specific behaviors that do not align with the flexibility and adaptability inherent to VAV systems. For instance, systems that operate at fixed airflow do not have the capability to adjust to varying demand, and those that heat or cool using constant airflow do not take full advantage of energy savings that come from modulating airflow based on real-time needs.