The application of natural ventilation in livestock farming still requires better understanding. Key issues are the configuration and dimensions of the ventilation openings throughout the barn. In this paper we tested the effect of six different ventilation opening configurations upon indoor air velocities, by means of Computational Fluid Dynamics (CFD). The 2D CFD results were verified with data from scale model experiments in a wind tunnel. Generally, both methods showed good agreement and indicated that larger ventilation openings resulted in lower air velocities near the inlet opening, but higher velocities at the outlet. Comparison with wind tunnel experiments also showed there is still room for improvement in the used CFD models. The obvious limitations of a 2D approach can be part of the explanation. Nevertheless, the main advantage of the computational approach was the ability to visualize the indoor airflows in each of the six geometries. Further research will involve 3D modelling.