Hot air systems utilize plastic tubing to convey incoming ventilation air. The tubing (Approx. 24-30 inches in diameter) is attached to a heating unit and runs the length of the greenhouse.
The warm air exits uniformly throughout the greenhouse through equally spaced holes of 2-3 inches in diameter which are spaced 36 inches apart along the entire length of the tubing. The plastic tubes can also be placed under the greenhouse benches to provide root-zone heating of the crop. Plastic skirts placed on the sides of the benches encourage the warm air to pass upward, warming both the root-zone and the crop canopy.