Two systems, one with air re-circulation alone and the other a combination of air re-circulation and energy recovery using plate heat exchangers have been analysed. For these systems, a set of equations was derived for partial or full re-circulation of air with and without plate heat exchangers. Also, as part of the analysis, the reciprocal ratio of investment and running costs was considered. In this analysis, the re-circulation factor provided by ventilation units, a bypass factor and the efficiency of a plate heat exchanger were considered to be variables.

A novel ventilation system has been installed in buildings constructed for the New Campus of the University of Nottingham. Super-efficient mechanical ventilation has been used as part of an integrated environmental strategy and operates with fan input powers below 0.5 W. l-1.  s-1 of airflow. The complete plant was assembled from innovative low-pressure components and has exceptional performance. A key element of the design is that components of the system are bypassed when not in use. At the heart of the system is a low-velocity, high efficiency thermal wheel.

Modern UK office buildings have a reputation of being energy profligate, largely due to the fan power requirements of commercial air conditioning. Most architects and HVAC designers only associate low-energy consumption with natural ventilation. However, the UK electricity utilities have peak maximum demands in winter, and buildings need to be designed for year-round lowenergy usage. Relatively few monitored studies of the total annual energy implications of natural and mechanical ventilation strategies operating in conjunction with fabric thermal storage have been published.

Making the controls contractor responsible for testing, adjusting and balancing would improve the process and reduce finger pointing.