Ventilation ducts with a high cross-sectional area are frequently built as structural ducts that include inside transversal structural beams. In this way, the cross-sectional area requested is respected, but the transverse structural elements will have a big impact on the airflow, with eventually additional noise and vibration and a high amount of energy wasted across the beams. From this perspective, the aim of this study is to evaluate the impact of the transversal beams inside the ventilation ducts, to analyze different alternatives for airflow improvement using computational fluid dynamics (CFD) simulation, and to check the simulation results in the wind tunnel with an experimental model. The results of the experimental measurements have highlighted the high-pressure drop and, consequently, the high energy wasted across the transversal structural beams. It was found that the airflow downstream of the beam is changing the flow direction, and high turbulences and vortices are initiated in the shadow of the beam. According to the CFD analysis, the ventilation system can be improved by adding airflow deflectors in the beam area. In this way, the high turbulences are reduced, the vortices and backflow are canceled, and the pressure losses across the beam area of the ventilation duct are reduced by up to 90% compared with the beam without a deflector. Therefore, the energy wasted in the beam area can be reduced by up to 90%.