Height is one of the most important aspects of a greenhouse. The height of a structure directly impacts on natural ventilation, the stability of the internal environment and crop management. Greenhouse structures with wall heights of at least 4 metres should be constructed wherever feasible. These structures should be built in preference to designs of lower height. The natural ‘chimney effect’ of rising hot air and falling cooler air which is the basis for passive ventilation becomes truly effective above approximately 3.5 metres.
A tall, roof ventilated greenhouse can achieve a more uniform, stable and ultimately superior growing environment for the crop. During hot weather, a taller structure avoids trapping heated, humid air around the plants.
Many of the problems that are encountered in greenhouse crops can be directly attributed to the capacity to manage the growing environment. Better control of the growing environment directly impacts on how well other problems in the greenhouse can be managed. A significant proportion of yield loss in Australian greenhouse crops can be attributed to poor management of heat. The capacity for a grower to manage heat in summer is greatly improved with increasing greenhouse height.
Effective management of pests and diseases using non-chemical management strategies is also dependent on good control of the growing environment and the value of height in the structure can not be overstated.
Although some crops can be grown relatively well in lower profile greenhouses, taller structures are more versatile, are suitable for a wider range of crops and therefore a better long term investment.