ENERGY EFFICIENT GREENHOUSES
Heating normally constitutes the major energy requirement for greenhouses. Measures that minimise heating requirement include designs that minimise surface area and maximise the penetration of solar radiation, heat conserving covering materials, and features that store day time solar energy for release into the greenhouse at night. As well as protecting plants against adverse climate and pests, a greenhouse provides an elevated temperature during the day. Unfortunately design aspects that best satisfy the requirements for solar energy penetration and heat retention, ie. a well sealed transparent enclosure, militate against many of the conditions required for optimum plant growth. Compared with outside, the climate in such a greenhouse is characterised by reduced solar radiation levels, high humidity, reduced carbon dioxide concentration and almost no air movement. In a properly designed greenhouse the often contradictory requirements for optimum plant environment and minimum energy requirement need to be given careful consideration. In many cases relatively simple methods can be employed to compensate for environmental deficiencies in energy efficient greenhouses. Where no such measures are available without seriously compromising the greenhouse design, an economic evaluation of the alternatives can be used to arrive at a solution that provides the best overall cost effectiveness.
Garzoli, K.V. (1989). ENERGY EFFICIENT GREENHOUSES. Acta Hortic. 245, 53-62