The manipulation of the greenhouse environment to achieve optimum growing conditions that will produce sustainable outcomes,in both economic and environmental terms,is still a significant challenge.In warm climates the main challenge remains the reduction of excessive temperature and humidity during the hot season.Improved ventilation of naturally ventilated greenhouses has been an important technological development that contributed to sustainable production.The utilization of air exchange theory into the design of greenhouse ventilation systems has resulted in greenhouse structures that can effectively ventilate under natural buoyancy and wind driven conditions.Still,however,in warm climates the use of insect-proof screens on the openings,to exclude insects,resulted in a warmer and more humid microclimate;a problem that needs to be solved.When ventilation does not sufficiently reduce the crop temperature,evaporative cooling is applied,a method that is now widely used.Techniques include sprinkling,fan and pad system and fogging.The hot dry conditions of some greenhouse regions are well sited to the combined use of fogging systems in conjunction with naturally ventilated greenhouse structures,an approach that is suitable to very large structures.This paper reviews few technologies that are related to the alleviation of heat load from greenhouses and discusses the applications of each technology.