Screen fabrics are a very popular shading material, and rightly so – they are robust, durable, come in large widths, an extensive range of weaves and colours and can often preserve the view to the outside.
Typically used in roller blind systems, screen materials have a range of technical performance characteristics but often it is the Openness (Openness Coefficient or Co) which is used as the specification criteria. However, this must be used with extreme caution.
Put simply, Openness is a measurement of the amount of holes in the fabric – it is not the measure of visible light transmission through the material. This is a measurement known as Tvis (or Tv), and fabric manufacturers should have their materials tested to European standards to be able to provide this data. (See our Jargon Buster for a simple explanation of all terms)
It is possible to have a higher light transmission with a low level of openness and vice versa, often depending on the colour of the material. This is explained in a short video here [HYPERLINK], or you can download our guidance note on this topic here [HYPERLINK]
For technical performance data on fabrics and materials manufactured to European standards which are then independently peer-reviewed, visit the European Solar Shading Database (ES-SDA), produced by the European Solar Shading Organisation (ES-SO).