Poly (vinyl chloride)/sodium montmorillonite (Na+-MMT) hybrid membranes with varied Na+-MMT content were prepared using casting processes for potential use in total heat recovery ventilation systems. The impact of Na+-MMT content on the morphology, thermal stability, mechanical property, gas transmission, pore diameters and total heat exchange effectiveness of the membranes were studied. It was observed that hybrid membranes with high content of Na+-MMT tended to have large roughness, improved thermal stability, high water vapor transmission as well as good temperature and enthalpy exchange effectiveness. With increasing Na+-MMT content, although the water desorption activation energy increased steadily together with the increased hydrophilic nature of the membranes, the water transmission rates increased dramatically caused by the introduction of larger pores in the systems. Balancing the requirement of low gas permeation, good water vapor and heat exchange effectiveness and mechanical properties, hybrid membranes with 60% Na+-MMT content seemed to have the highest potential to be used as Total Heat Recovery membranes in energy saving ventilation systems. (C) 2013 Elsevier B.V. All rights reserved.