ISHS Acta Horticulturae 115: Symposium on More Profitable Use of Energy in Protected Cultivation
INFLUENCE OF COVER MATERIAL ON HEAT LOSSES FROM A GLASS HOUSE : COMPARISON BETWEEN STANDARD GLASS AND LOW EMISSIVITY GLASS |
| Authors: | M. Baille, J. Damagnez, J.C. Laury |
| Abstract:
We have studied the influence of a Low Emissivity Glass (L.E.G.) cover on heat losses from a greenhouse during the season 1979–1980. This cover has, on one side, a thin layer of stain oxide which confers it an emissivity coefficient for infrared radiation (  > 3 μm) lower than that of standard glass.
The differences in behaviour with a standard glasshouse depend on the relative weight of radiative and convective losses in the total balance. The best results with L.E.G. are obtained on clear nights with low wind : the temperature differences in actinothermal index (which is an estimate of resulting temperature of plant cover by night) with a standard glasshouse can reach 2° C with the same setpoint air temperature. This result leads to a saving in energy consumption which varies from 5 to 40 % as a function of outside climate, with a mean saving of 20 % under a climate with moderate cloud cover and winds. The disadvantages inherent to using this cover concern, on the one hand the P.A.R. reduction, and on the other hand, the relative unefficiency of L.E.G. under strong wind or rainy weather. | |
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