Chapter 5

Greenhouse Energy Conservation Strategies

Greenhouse Shade Management

Shading is applied primarily used to reduce indoor light intensity and help control temperature during the day. A semi-porous curtain made of aluminized materials used for shading can reduce the temperature in the greenhouse by about 10 degrees F. This reduces the cooling costs of using fans or evaporative cooling and may improve plant quality. There are two general strategies used to provide shading to greenhouses: application of a shading compound such as white wash and installation of a shade curtain.

Greenhouse Shading Compounds

Shading compound, or white wash, is commonly used because it is relatively inexpensive to apply, can be used on any glazing material and structure, and reflect light outside the greenhouse before it enters and increases temperature. Shade compound is a paint-like substance applied to a greenhouse covering by spraying. When dry the compound leaves a white film, which reflects up to 50 percent of the solar radiation.

Greenhouse Shade Curtains

Another procedure for shading consists of installing a retractable shade curtain inside the greenhouse above the crop or, less commonly, outside the greenhouse structure. When a curtain is located inside, solar energy is allowed to enter the greenhouse before it is reflected. This can cause heat to build above the shading material, which increases the need for roof vents. Interior retractable shading is commonly used with natural ventilation. When the roof vent opens, the retractable shade closes or partially closes, allowing for even shading and ventilation through the shade. Although shade curtains are relatively expensive, they allow light to be more precisely controlled, which can improve crop quality. The ability to retract screens during periods of low light is an important attribute of this technology.

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