FAN AND PAD COOLING OF GREENHOUSES
Fifty million square feet of greenhouse area has been equipped with fan and pad cooling systems since the first system was invented in 1954. The most used pad material is shredded aspen wood, which provides the maximum dry bulb depression when the air is moved at 150 feet per minute. The efficiency of the fan and pad cooling system is approximately 85% which means that the air leaving the pad has been cooled 85% of the difference between the wet and dry bulb temperature of the incoming air. One air change per minute in the growing area is used to size the fans and pads. Thermostats and time clocks are used to control the system automatically. Before installing a fan and pad system, one should be aware that insects may be drawn in through open spaces in the pads, the pads may become clogged with mineral deposits, and some rose growers have attributed excessive mildew to this cooling system.
BAILEY, W. A. (1968). FAN AND PAD COOLING OF GREENHOUSES. Acta Hortic. 6, 109-121