Agra Tech has developed Agra Kool II, a positive pressure cooling system. High volume jet-fans pull air through an evaporative cooling system and force it into the greenhouse through special convection tubes. This raises the static pressure inside the greenhouse. Integrated pressure sensitive ridge vents maintain the optimum pressure inside and allow heat to exit. The temperature differential with a positive pressure system can be as low as 2 degrees Fahrenheit compared to a 7 degree differential for negative pressure (fan and pad) system.*
Another big advantage of the Agra Kool II positive pressure system is how it fights insect intrusion. The small opening in the roof vents with positive air flow from inside of the house acts like an air curtain making it much harder for insects to enter. Also, the roof vents can be screened, virtually eliminating insect entry. This reduces the need for pesticides.
While installation and operating costs of a positive pressure cooling system may be higher than a negative pressure cooling system, the advantages of more even cooling and pest control may result in a quick return on your investment.
* See article Positive Pressure on our blog for more information about Agra Kool II.