Ventilation systems deliver conditioned air to occupied spaces. Depending on the building type, ventilation air may be comprised of 100% outside air, such as in a laboratory building, or some mixture of re-circulated interior air and outside air. In commercial and institutional buildings, there are a number of different types of systems for delivering this air:
- Constant air volume (CAV) systems deliver a constant rate of air while varying the temperature of the supply air.
- Variable air volume systems (VAV) vary the amount of air supplied to a zone while holding the supply air temperature constant.
- Fan-powered variable air volume terminal units provide another method to improve air distribution at low load conditions. These units combine the benefits of a VAV system, by reducing central fan energy and reheat energy, with the benefits of a CAV system, by maintaining good airflow.
- Raised floor air distribution delivers air low in the space, at low velocity and relatively high temperature compared to traditional plenum mounted distribution systems. Delivering air through a series of adjustable floor-mounted registers permits room air to be stratified with lower temperatures in the bottom portion of the room where people are located and high temperatures towards the ceiling. This system type is attracting increasing interest because it has the potential to save energy and to provide a high degree of individual comfort control.