A novel vapor-permeable composite membrane for air dehumidification has been fabricated. The membrane used porous polyethersulfone (PES) as the support layer, and dense polyvinyl alcohol (PVA) as the active separating layer. To facilitate moisture permeation, lithium chloride (LiCl) salts were used as an additive to the PVA solution before it was cast onto the support layer. The effects of the LiCl concentration on the water vapor permeability are investigated. The permeation tests indicate that the addition of LiCl in PVA cast solution can improve vapor permeability substantially. The observations of the microstructures and the characterization of the synthesized material disclosed that the reason behind increased moisture rates is that the addition of LiCl increased the hydrophilicity. (c) 2007 Elsevier B.V. All rights reserved.