CAV, VAV and DCV, 3 priniciples for controlling airflow

Experience from and studies on offices show that the average required airflow is somewhat lower than the dimensioned airflow.

Often a proportion of the staff will be away, either at meetings, on courses or off sick. Or there may be meeting rooms which are not used all the time, leading to highly variable ventilation requirements.

For this reason demand-controlled ventilation is necessary to avoid unnecessary wasting of energy.

Control principles

Demand control is an intelligent way of saving energy consumption on ventilation.

By reducing airflow when there is no-one in a room or building, or regulating airflow to the required load, energy is saved (less outdoor air to warm up) and, at the same time, the electrical consumption of the fans is reduced.

Three different control principles are employed, either individually or in combination, in a ventilation system:

- CAV - Constant air volume
- VAV - Variable air volume
- DCV - Demand controlled air volume

The following graph shows the energy consumption for each control principle (power and heat).