A model for the thermal conductivity of two-phase composite porous media, such as adsorbing desiccant bed with inert material, is presented. The unit cell model is extended to account for the inert materials and moisture sorbed in pores; and the effect of porosity, water content and presence of inert material is determined. The prediction of the effective thermal conductivity from this proposed model is compared with that given by other available models and experimental data and the proposed model is used to investigate the effect of porosity, water content and presence of inert material.