Glare from a translucent façade, evaluation with an experimental method

• Translucent facades (LT > 29%) may cause noticeable, disturbing and intolerable glare (φ > 60° too).
• The sensation of glare differs enormously between subjects.
• Reading speed on EVD in glary conditions can be increased by adjustment of reading geometry.

The paper addresses the problem of glare in buildings with translucent façades. The study was carried out using a physical test-model on sunny days in the period March–November 2011 in Trondheim, Norway.Looking inside the model, each of the 21 subjects evaluated the glare sensation on a scale from barely perceptive to intolerable. They were also asked to read out loud a text on a mobile phone placed inside the model. At the same time, a scientific assistant measured the reading speed. In addition, measurements of the outside vertical illuminance, the inside luminance of the translucent wall element and the vertical illuminance at the subject’s eye position were taken. The subjects were also asked to evaluate the difficulty of reading.The study shows that translucent facades may cause both, a sensation of glare and a reduction in reading speed in sunny days in buildings situated at high latitudes (63°) and that there are huge differences between subjects. The hypothesis that the sensation of glare may be reduced if a part of a façade enables an outside view could not be evidenced. The reading speed in glary setting may be significantly increased i.e. up to 40% if subjects have a possibility to fine adjust the position of the display.