How to choose the right type of glass for a greenhouse?

In the choice of the type of glass on the deck of the modern greenhouses, more and more possible options appear on the market each year. There is the possibility of applying an anti-reflection coating (AR coating) or adding a haze-treatment (diffuse glass). AR coating will reduce the reflection of (sun-) light. Diffuse glass ensures that the light in the greenhouse will be diffracted. The degree of diffraction will determine the haze factor. A haze factor of 50 means that 50% of the incident light is diffracted.

Both the AR coating and the diffusing has become cheaper, leading to a more appealing cost-benefit analysis. The quality of the glass to be used is determined by means of light measurements, in which is measured which part of the incident light is transmitted. The vertical transmission value with modern glass lies well above 90%. The rest of the light is reflected and absorbed.

However, the perpendicular incidence, is only part of the story. The position of the sun has an effect on the amount of light that is absorbed and reflected. The larger the angle is compared to the perpendicular, the lower the light transmission. This effect, which applies to both untreated and treated glass, can be determined in a so-called hemispherical measurement. A high vertical transmission does not necessarily mean a high transmission in non-perpendicular light angle.

For a southern European location, Agro Consultancy recently mapped the impact of the various glass treatments on the light transmission in the greenhouse. Which answered questions such as:

With these calculation methods, Agro Adviesbureau is able to determine the most suitable glass type for any location in the world. 

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René Caron