A mathematical model was developed to analyze the heat and mass transfer in the core of a membrane-based enthalpy exchanger, and equations for evaluating the thermal and moisture resistances were derived. Calculations were conducted to investigate the effects of the membrane parameters on the exchanger performance. The membrane parameters include the moisture diffusivity, thermal conductivity, moisture sorption constant, and maximum moisture uptake. The calculation results are presented and interpreted in terms of the thermal and moisture resistances. The sensible effectiveness shows a limited change with the membrane parameters because the thermal resistance of the membrane accounts for only a small fraction of the total thermal resistance. The latent effectiveness, basically, change more significantly with the membrane parameters. The enthalpy effectiveness lies between the sensible and the latent effectiveness but locates closer to the latent effectiveness because the latent heat predominates over the sensible heat. (C) 2009 Elsevier B.V. All rights reserved.