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Natural convection with high cooling effects is of increasing interest in cold region geotechnical engineering. To study natural air convection in a highly-permeable porous medium, convective and conductive heat transfer experiments were carried out using an insulated cylindrical tank filled with styrofoam chips. Convection and conduction were caused by controlling the temperatures at the top and bottom of the tank, and a series of cross-sectional conductive and convective isotherms were generated from collected temperature data. Additional convective patterns were obtained from tests by centrally localized heating below or cooling above. Flow velocities were measured at the center of the tank. Results showed that convective heat transfer rate was higher than thermal conduction. Convective isothermal patterns varied with various boundary conditions and could be influenced by small temperature perturbation. Given appropriate environmental conditions, efficient convective cooling effects can be used to enhance ground freezing or to protect permafrost from degradation. / Geotechnical Engineering