Cooler on summer days

The modern 9 ha chrysanthemum nursery of Dirk-Jan Breugem came into operation at the end of 2008. Every year it produces 27 million chrysanthemums, 95% of which are sold outside the Netherlands. An assimilation lighting installation and the OBSCURA blackout screen create the right level of light to be able to supply chrysanthemums all year round. A day length of no more than 13 hours is allowed to bring chrysanthemums into bloom, and this is realised in summer by closing the blackout screen in the afternoon.

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The main reason for choosing the OBSCURA 10070 FR WB+B were the flame-retardant properties of the screen. Then, after a few years of working with the blackout screen, it struck Dirk-Jan that the temperature in the greenhouse when it was closed on hot summer afternoons was lower than with the blackout screen at his previous business: the upper side of the OBSCURA 10070 FR WB+B is white, whereas the screen at his previous business was finished with an aluminum upper side. The lower temperature beneath the blackout screen is a major advantage, because it is not possible to keep a gap in the screen before sunset to provide a cooler climate for the chrysanthemums. 

How a blackout screen transfers moisture is also important to Breugem. In the sections with fully-grown chrysanthemums there is a lot of evaporation, and this moisture clings to the screen. A screen with limited moisture transmission creates too much “condensation rain” on the chrysanthemums, leading to a deterioration in quality. His new blackout screen performs far better here than the blackout screen at his previous business.

On high summer days the sun is screened out in the harvesting area by closing the blackout screen for 80%. This screening is gauged not on the basis of sun radiation, but purely on when the chrysanthemums start to droop. Dirk-Jan suggests a possible new development in the area of screens for chrysanthemums: install a summer screen above the blackout screen. Whether this is worthwhile and profitable will depend on the type of chrysanthemums. 

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