We present a study of the performance of desiccant felt with inert materials. An effective thermal conductivity model that accounts for the inert materials, the moisture sorbed in pores, and the effect of porosity and water content is incorporated into a heat- and mass-transfer model to study the sorption processes of water vapor in a desiccant dehumidifier. The dehumidifier consists of parallel flow channels. Results are presented for different fractions and different ratios of thermal conductivities and capacitances of inert and desiccant materials.