Window 1 has an external roller blind fitted with a screen fabric in Black, Window 2 has an internal roller blind using a metalised polyester filter, and Window 3 has the same filter on a motorised blind between the panes of a sealed unit.
De Leeuw Ltd. staff will be showing how the position, construction and colour (spectral properties) of the shading fabric can be as important as the specification of the glazing and how it can be particularly successful in rescuing new build specification oversights. *
A 22-page laboratory report by Sonnergy Ltd, focusing on the reflectance, absorbance and transmission of solar energy, commissioned by De Leeuw Ltd., demonstrates not only the significantly differing performances between the Black and the White fabrics, the difference between an internal blind and an external blind but goes on to quantify them. All taking into account the glass specification (to standards defined in EN- 13363-1 drawing on EN 1450 and EN 14501).
Example: Double clear glass with low E coating is rated as allowing a total solar energy transmittance (g value) of 0.72, put the White screen fabric with this glazing as an internal blind, and the value (g tot) improves to 0.39, but the same fabric in Black, mounted externally takes the value to an entirely different level of 0.11.
For light control, the positioning internally or externally is not relevant but the White fabric will permit 23% of the visible light to pass whilst the Black will take it down to 6%. But what if you are faced with daylight levels of 40,000 + lux and you need to get levels in your office down to the recommended working levels of 300 to 500 lux?
Copies of the report will be available, free of charge, post show to stand visitors. Initially produced for insertion in the BBSA Shade Projects database, the data is relevant to specifiers on its own, right now. If specifying a new build or refurbishment and concerned about heat build-up (solar gain) and levels of light/glare, then contact Reflex-Rol now for details of solar shading materials, suitable hardware and methods of operation and control.
* Reflex-Rol even has an acoustic solution for the reduction of speech reverberation.
Photo: Passage of the sun, Clifton Suspension Bridge (Bristol, UK), December 17th 2007 to June 21st 2008. Photographer Justin Quinnell, www.pinholephotography.org