Energy savings by installing variable air volume systems (VAV) in existing office buildings

In commercial buildings a CAV (constant air volume) system is normally used for ventilation and air-conditioning.  In order to keep the room temperature in required level during the summer period quite high airflow rates and higher amounts of energy for heating and distribution of air are needed. By changing the system to VAV operation, considerable energy savings can be achieved. However, such a change becomes meaningful only if the system as a whole is adapted to the new way of operation. The critical components are the supply air terminal devices, which must have good controlling properties, a low noise level and provide a comfortable air flow and temperature pattern in the room within the variable volume flow range in question. The paper accounts for experiences from a reconstruction from CAV to VAV in a 5000 m2 about 40 year old office building. Investigations were carried out with new type of supply air devices, which were installed in this office building.