In many parts of the United States, cooling a greenhouse is a greater problem than heating it. When ventilation will not control temperature, shading can be used. By reflecting the sun's rays or blocking them so they can't get into the house, a significant portidn of the heat load is removed. This can reduce electricity use associated with fan ventilation systems. The heat load is created by the infrared wavelengths of the radiant energy from the sun. Plants are photosynthetically active in the blueto red range (380-700 nanometers) of the total light spectrum.
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