VAV air conditioning systems are considered to be more energy efficient than many other types of air distribution system because they can minimise fan energy consumption at part load operating conditions. However, previous work by BRE for DETR has shown that the predicted energy savings are not achieved in practice due to factors such as incorrect fan static pressure sensor location, use of inefficient fan speed control methods and system installation effects. This report presents the results of a critical review of a number of papers, reports and relevant guidance documents on variable air volume (VAV) air conditioning systems published in the UK and USA. In each case an abstract is given with an interpretation of the main points of each document. The report concentrates on the role of the building engineering services designer with responsibilities for the complete package, including the construction commissioning, testing and maintenance of the installation. To increase awareness of design techniques for enhancing the energy efficiency of VAV air conditioning systems, each review identifies specific and definitive (rather than general) design information. 66 pages.