What is VAV in HVAC?

March 15, 20241

What is VAV in HVAC?

VAV stands for Variable Air Volume. It’s a type of HVAC system designed to deliver varying amounts of air to different zones within a building, depending on the cooling or heating needs of each specific area. This approach offers several advantages over traditional constant air volume (CAV) systems.

Here’s a breakdown of how VAV systems work:

Central Air Handling Unit (AHU): The AHU conditions the air (heating, cooling, dehumidifying) and supplies it to the building.
Variable Airflow: Unlike CAV systems that deliver a constant airflow, VAV systems adjust the airflow based on the demand.
Zone Control: Each zone (room, section of a floor) has a VAV terminal unit or VAV box with a sensor (usually a thermostat) that detects the temperature.
Demand Response: The sensor in the VAV box sends a signal to the terminal unit, which adjusts a damper to regulate the airflow.

Benefits of VAV Systems:

Improved Comfort: Provides more precise temperature control in different zones, leading to better occupant comfort.
Energy Efficiency: By delivering only the necessary amount of air, VAV systems can significantly reduce energy consumption compared to CAV systems.
Reduced Noise: Less overall airflow can lead to quieter operation of the HVAC system.

Here’s a table summarizing the key points:

Feature	VAV System	CAV System
Airflow Delivery	Variable based on zone demand	Constant airflow throughout the building
Temperature Control	More precise control in each zone	Consistent temperature across the building
Energy Efficiency	More energy-efficient	Less energy-efficient
Noise Level	Potentially quieter operation	Potentially louder due to constant airflow

However, VAV systems can also have some drawbacks:

Complexity: Compared to CAV systems, VAV systems have more complex controls and require proper maintenance.
Cost: The initial installation cost of a VAV system might be higher than a CAV system.

What is VAV in HVAC?