O. Skov
The traditional way of building and siting greenhouses in Denmark makes one roof surface face north and the other face south.

As solar transmission varies over the day and over the year it is evident that the surface facing south transmits the largest amount of sun radiation. The question is, however: How big is the difference? And what influence does this difference have on the choice of covering material for the greenhouse and screen systems?

In a greenhouse 12 m wide built at SBI the solar transmission is measured for the roof surfaces facing north and south under a single layer of glass and under a double acrylic plate.

The findings up till now show that even at an intensity of the solar transmission of 450 W/m2 during the months of winter (October-March) solar transmission will not exceed 60 W/m2 as regards the roof surface facing north, and that during the months of spring (April-May) at an intensity of 800 W/m2 the solar transmission will not exceed 350 W/m2 as regards the surface facing north.

Also, the findings show that it is possible to replace a single layer of glass in the roof surface facing north by a double acrylic plate without reducing the total solar transmission over the year. In greenhouses with shading screen systems the radiation can be improved by parting the system in such a way that the screens can be drawn individually and by mounting different types of screens on the north and on the south side.

Skov, O. (1989). LIGHT TRANSMISSION IN GREENHOUSES. Acta Hortic. 245, 86-93
DOI: 10.17660/ActaHortic.1989.245.9

Acta Horticulturae