PLANT RESPONSE AND ENERGY USE IN FIVE HIGH THERMAL RESISTANCE GREENHOUSES
An experimental comparison was made of the energy consumption, environment and growth of tomatoes in greenhouse compartments covered with single glass and 5 high thermal resistance materials. The energy savings obtained were 57% with triple acrylic, 42% with double polycarbonate, 36% with double acrylic, 18% with double glass and 13% with low emissivity glass. The air leakage rate of the double glass compartment was twice as large as the others. The vapour pressure deficits at night were lower in the more insulated compartments, but the differences were smaller during the day. The tomato yields correlated with the photosynthetically active radiation received from the start of harvest, a 1% light reduction giving a 1% yield reduction. The reductions in yield compared to the single glazed compartment were 17, 10, 1, 9 and 5% respectively for triple acrylic, double polycarbonate, double acrylic, double glass and low emissivity glass. The reductions occurred mainly because of a decrease in the number of fruit, but also because a higher proportion of the fruit was smaller. An economic assessment showed that none of the high thermal resistance covering materials was superior to glass for producing early tomatoes in the United Kingdom.
Bailey, B.J. and Hunter, A. (1988). PLANT RESPONSE AND ENERGY USE IN FIVE HIGH THERMAL RESISTANCE GREENHOUSES. Acta Hortic. 229, 165-172