Subjective assessment of visual comfort in a daylit workplace with an electrochromic glazed facade

Electrochromic (EC) glazing is increasingly employed in building facades to achieve better visual comfort for the occupants. EC glazing can modulate the light entering through the facade by varying the solar transmittance of the glass and therefore can work as a shading strategy to minimize solar heat gains or glare. However, it also alters the spectrum and distribution of light entering through the facade, which influences certain visual attributes associated with a space. This user assessment study evaluates some of these attributes including the colour perception of the elements inside and outside the room, the uniformity of daylight distribution, the clarity of the view through the glazing and the perception of glare when the sun is in the field of view. Results indicate a visual transmittance (tv) of 0.6% is sufficient to control glare when the sun is in the peripheral field of view (FOV) while tv, n-n of 0.14% is required to control glare when the sun is close to the central FOV. Most of the participants did not perceive the colours of outdoor environment as natural when seen through EC glazed window. The majority of participants also desired to change the glazing configuration by adding an additional shading device.