Greenhouse tomatoes with indeterminate growth habits are best managed in houses with high roofs. The structural design of a greenhouse must provide protection from wind, rain, heat and cold. The structural supports must be of minimal size to permit maximum light transmission to the crop while still supporting the structure itself, heating and ventilation units and the weight of the crop which is trained to grow up a support system carried by the greenhouse frame. There are a variety of types of greenhouse covers. Glass is still a common glazing material.
Large panes reduce the shading of the crop from the support frame.
Despite the common use of glass as a covering for greenhouses in Northwest Europe, glass remains inflexible, heavy, and expensive. In contrast, the quantity of plastic used for greenhouses is increasing rapidly. Since polyethylene sheet film was first developed in England in 1938, it has been used widely in greenhouses because it is easy to work with and inexpensive. Worldwide, there are nearly 300,000 ha. Several other plastics have also been used for greenhouse glazings.