THE EVALUATION OF THERMAL SCREENS IN GLASSHOUSES ON COMMERCIAL NURSERIES
During the 1979 season measurements were made of heat consumption and glasshouse air temperature, and crop yields were recorded by the growers. The screens were used each night for approximately four months from the time of planting. The nocturnal heat requirement of the screened houses was 60% less than that of the unscreened houses for the same internal air temperatures. However, the yield of tomatoes from the screened house, was 6–9% lower than from the unscreened ones. Prior to the following season the insulation on the external walls was modified so it could be removed during the day. Measurements were made of leaf temperature and the transmittance of photosynthetically active radiation by the screened and non-screened glasshouses. Crop response in the screened houses at both nurseries was similar to that in the unscreened houses over the early part of the season.