Studies of zeolite membranes for gas separations, including natural gas purification, biogas purifications, and CO2/N-2 separation are well documented. In this paper, using CO2/N-2 separation as a model system, we examine a series of zeolite (faujasite)/polymer composite membranes. These zeolite membranes were prepared by growing a continuous zeolite layer within a porous poly(ether sulfone) (PES) support followed by a polydimethylsiloxane (PDMS) coating layer to fix defects in the zeolite/PES layer. The effect of PDMS cross-linking, humidity in the feed gas (46 ppm), and temperature on the transport properties were studied. The separation performance was significantly improved with 'membranes that used cross-linked PDMS versus un-cross-linked PDMS. At room temperature, the introduction of humidity completely suppressed CO2/N-2 separation. With higher temperatures, the effect of humidity on CO2/N-2 separation performance was alleviated to some extent. Exposure to humidity at high temperature led to poor recovery of transport properties upon reexamination of the same membrane with dry gases at room temperature. An improvement in recovery was observed if the zeolite membrane surface was made hydrophobic via ion-exchange with hexadecylamine: This suggests that water can be trapped at the hydrophobic hydrophilic PDMS zeolite interface; making the surface hydrophobic assists in removal of the trapped interfacial water. Practical applications of such membranes are limited to dry gas separations.