Glare from daylighting in buildings

Glare can be caused by a direct view of the bright sky from the interior of a building. This glare can be an impediment to vision and even a direct hazard, as on a stairway, or it can cause serious or mild discomfort. Even minor effects may accumulate, as with a low but incessant noise, to lead to fatigue during the working day. Both the disabling and annoying effects of glare have been studied in a number of laboratories, and this article summarises some of the most recent conclusions. Glare is a direct function of both the size of the window and the brightness of the sky seen through it, and an inverse function of the brightness of the room interior. Glare can therefore be reduced by cutting down the size and brightness of the visible patch of sky and by increasing the interior brightness by the judicious use of surface areas of high reflectance. These parameters are related in such a way that an overall Glare Index for a room can be computed and values of this Glare Index can be set and codified to ensure that tolerance limits will not be exceeded.