In the design phase of a test site in Indonesia computational fluid dynamics has been used to design the construction of the plastic greenhouse. Greenhouses in Indonesia are built to protect the crop from heavy rain and insects. The climate in four different greenhouse designs is calculated without insect gauze and with two types of insect gauze in the openings. Two designs consist of greenhouses with a top opening at one side of the ridge, with different dimensions of the top opening. The third design has no top opening, and the fourth design is the conventional Indonesian design consisting of three spans with an opening on one side of the ridges. The walls of the greenhouses are open or covered by insect gaze. The ground area in the greenhouse is equal for all designs. The ventilation rate and the maximum temperature in the greenhouse have been used to evaluate the designs. The influence of the wind speed and direction has been investigated. The design without an opening in the top has the highest ventilation rate and the lowest maximum temperature in case of wind due to aerodynamics. In case of no wind the climate in the design without top ventilation is slightly worse than in the other designs. Increasing the length of the greenhouse reduces the ventilation for this design. The insect gauze reduces the ventilation by more than 50%. Based on these results a new design has been developed with an aerodynamic top opening. This design proved to function with and without wind. This design is currently being tested in Indonesia.