This article examines the buoyancy induced circulation occurring on both sides of a vertical impermeable partition separating two semi-infinite porous reservoirs maintained at different temperatures. The circulation is found to consist of two counterflowing boundary layers which interact thermally across the partition, transferring heat from the hot side to the cold side. The net heat transfer rate is calculated and the effect of the thickness and conductivity of the partition on the heat transfer rate is determined. It is demonstrated that the insertion of a vertical impermeable partition in the middle of a vertical porous layer reduces significantly the net heat transfer rate through the layer. © 1981.