An experimental investigation has been carried out to determine the operating performance of a rotating regenerative total energy wheel (TEW). A total energy wheel is a device which conserves both sensible and latent energies. It transfers heat from a warmer to a cooler airstream while simultaneously transferring moisture from a more humid to a less humid airstream. The effectiveness of a TEW device has been measured in a special experimental facility which incorporates features that enable the obtainment of data of high accuracy. The heart of the facility is a spacious, compartmented plenum chamber made from extruded, closed-cell polystyrene which is free of extraneous heat transfer and air leakage. The plenum allows for well-defined inlet and exit conditions for the heat/moisture exchanger being evaluated. Only the plenum need be reconfigured to accommodate each heat/moisture exchanger type, a task that can be performed in a day. The remainder of the facility is universal for all heat/moisture exchangers. Most of the instrumentation is located in the universal part of the facility and is not affected by plenum reconfigurations. (c) 2006 Published by Elsevier Ltd.