Diffuus Glas

Diffuus Glass

Duration: 2016 - 2017
Point of contact: S. Hemming / E-MAIL: silke.hemming@wur.nl
Knowledge institute: Wageningen UR Glastuinbouw


The aim of this project is to arrive at a protocol, assessment method and approach for measuring the optical characteristics of (diffuse) greenhouse covering materials and shading materials, supported by all stakeholders (manufacturers, growers, greenhouse design companies, construction and installation companies, glass distributors, consultants and knowledge institutes) and formalised in an NEN standard. The reason for this is that the existing (international) standards are no longer sufficient for new (diffuse) materials as used in modern-day greenhouse projects.


Revised standards for determining the light transmittance of horticultural glass

In a PPS project under the flag of "de topsector Tuinbouw & Uitgangsmateriaal", Wageningen University & Research, the supply industry, LTO Glaskracht Nederland and NEN have developed new NEN standards.

These standards are for determining light transmission and scattering of greenhouse covering materials and screens and also for a sampling procedure for checking the transmittance of glass delivered to the client. Since the introduction of diffuse glass the previous standards were no longer appropriate and no standard was available for horticultural screens and seasonal coatings.

The new NEN2675 describes, next to the PAR transmittance, also transmittance for Ultraviolet (UV), near-infrared (NIR) as well as the solar factor. For light scattering a new term is introduced: the Hortiscatter. This is much more appropriate for greenhouse glass and has to replace the Haze measurement which comes original from the plastics industry.

Also the sampling procedure (NEN2674) has been revised thoroughly. The previous standard requires measuring according to the previous NEN2675 (only applies for clear glass) which makes it practically unusable. Likewise, the old sampling procedure requires a large number of samples, even at small batches. For this reason the standard was used barely.

At current greenhouse construction sites batches are even larger and would require even more samples. In the revised sampling procedure a limited amount of panes are selected by the supplier as well as the client and stored properly. In a later stage these could be measured according to the new standard. Currently the consortium agrees about both revised standards.


  • Alcomij B.V.
  • Boal systems
  • Certhon
  • Dalsem
  • Gakon
  • J.M Van der Hoeven
  • Maurice Kassenbouw
  • Prins Group
  • Glasimport Greenhouses
  • Glascom BV
  • Hermadix Agro BV
  • Ludvig Svensson BV
  • Mardenkro BV
  • Metazet
  • Ridder Climate Screens
  • Saint-Gobain Cultilène BV