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Another way in which greenhouse covers can impact the energy use is through their PAR transmission - especially in regions receiving lesser light in the winters, if PAR transmission is not maximized, the light needs would have to be met by artificial illumination, which will also increase energy consumption.
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The impact of the cover on the internal temperature of the greenhouse and the heating/cooling demand of the greenhouse means that it will also affect transpiration - the mechanism used by the crop to cool itself - and consequently the water-use in the greenhouse. Particularly in warm and dry climates, employing evaporative cooling (fogging and pad and fan) to get rid of excessive energy input could further increase the water consumption.
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It should be noted, however, that except when the property-modifying coatings are temporary, the properties of the cover remain constant across the entire period of its use. For instance, low-emission covers of temperate greenhouses might contribute to increased energy savings in cold periods, but in warmer periods, this will lead to undesirable retention of excess heat. Until materials can be developed that can switch their properties without a significant consumption of energy, a more tunable control on the optical properties and energy use of the greenhouse can be attained through the use of energy screens.
More information about the greenhouse cover can be found on the KasKieswijzer.
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