Air to air heat exchangers play a crucial role in mechanical ventilation equipment, due to potential primary energy savings in new buildings or in case of refurbishment of existing ones. In particular, interest in enthalpy wheels is increasing due to their low pressure drop and high effectiveness. In this work two different enthalpy wheels, a silica gel and a calcium carbonate based wheel, respectively, are tested. Sensible and latent effectiveness are evaluated in many working conditions, in particular with balanced and unbalanced air flows and with different inlet air temperature, humidity and wheel revolution speed. For each wheel, at nominal revolution speed, practical correlations of sensible and latent effectiveness and of pressure drop are proposed. The obtained correlations predict appropriately actual enthalpy wheels performance. Therefore they can be easily used in energy simulation programs to predict effectiveness and pressure drop of enthalpy wheels used for heat and water vapour recovery in buildings. (C) 2014 Elsevier B.V. All rights reserved.