The control of humidity in buildings or industrial process streams plays a key role in overall energy efficiency or in the reduction of corrosion. We have developed hydrophilic membranes with a high water vapor transfer rate and a low air leakage which can be used for fuel cells or drying applications. Therefore we apply thin polymer coatings on flat or hollow fiber membranes (both outside and inside coating possible). We have built-up excellent infrastructure for the characterization of such membranes. The water transfer rate can be automatically measured at different temperatures, pressures and humidities. In addition, air leakage or mechanical properties can be determined.