G. Giacomelli, W. Roberts
The need for cooling in greenhouses is nearly universal. Few areas of the world escape this requirement. Increased interest has been stimulated by the development of high-pressure mist systems that are proving to be effective in many greenhouse applications.

Previous studies on evaporative cooling systems have demonstrated the influence of greenhouse relative humidity on the leaf temperature of a plant. As relative humidity increases, the rate of evapotranspiration (evaporation from the leaf) decreases. In times of high direct solar radiation, the leaf temperature could be as much as 3.5°F warmer than the air temperature.

Relative humidity is expressed as a percentage of the actual amount of moisture present in the air to the maximum amount of moisture that the air may contain at a particular temperature. It is one of the more difficult greenhouse environmental parameters to measure.

Giacomelli, G. and Roberts, W. (1989). TRY ALTERNATE METHODS OF EVAPORATIVE COOLING. Acta Hortic. 257, 29-30
DOI: 10.17660/ActaHortic.1989.257.4

Acta Horticulturae