This paper introduces a numerical methodology based on a 3D turbulent flow computation developed to assess the aerodynamic performances of lumber drying kilns. The numerical results are validated against experimental data obtained by applying five different fan speeds and reversible air flow. The distributions of the energy loss coefficient and of the non-uniformity flow coefficient were plotted along the flow path in both normal and reverse directions and the regions with larger air loss values were identified. The numerical computation revealed that three quarters of the airfl ow delivered by the fans bypasses the wood stacks through different gaps, consequently leading to a low aerodynamic effi ciency (of 24-25 %) of the kiln.