Computational fluid dynamics (CFD) simulations can be a valuable tool for analysing the internal air flow and understanding the functionality of the greenhouse structural characteristics with respect to ventilation. In this work, a demonstration of CFD simulations used as a design tool for more efficient greenhouse ventilation is presented. The detailed picture of the average flow offered by the CFD results allows the analysis of the ventilation mechanism in a structure. In this way, the size, position and shape of the ventilators can be designed so that the indoor air mixes smoothly without forming stagnant regions and the overall ventilation capacity improves.