A novel effective medium theory was proposed to model the thermal conductivity of porous materials. In this theory, phases (or components) are treated as small spheres dispersing into an assumed uniform medium with the thermal conductivity km. A simple algebraic expression for the thermal conductivity based on this theory was derived, in which each has a distinct physical basis. The expression can unify five basic structural models (Series, Parallel, two forms of Maxwell-Eucken, effective medium theory) through variations of k(m). Furthermore, the feasibility of the model was evaluated using the experimental data from previous literatures and those calculated by this model. (C) 2013 Elsevier Ltd. All rights reserved.