In the last decade, computational fluid dynamics (CFD) has been used to evaluate ventilation on agricultural facilities, mainly on greenhouses. However, there is lack of information on aerodynamic design on greenhouses. In this work, a CFD model has been used to evaluate wind forces over plastic greenhouse covers. Two different greenhouse geometries plane and round, were studied. The effect of wind velocity on the pressure profile over the greenhouses was evaluated. Results showed that almost the entirely roof is subjected to suction forces for both geometries. For the round geometry, these forces are bigger than for plane geometry. However, a bigger damage is observed on plane geometries. From the results, it can be concluded that flapping is the cause of plastic tearing.