(in German)

The task of lightwells is to distribute daylight into adjacent spaces. When oriented to a lightwell workrooms receive daylight primarily reflected off the lightwells walls.

As the study showed, a daylight factor of 2 % can be achieved at a workstation near a window with a height to width ratio of the lightwell of 1.2. According to the technical rule for workplaces ASR A3.4 a daylight factor of 2 % allows the assumption, that the requirements for sufficient daylight have been met. With slimmer dimensions of the lightwell, the required daylight factor is hardly to achieve.

ASR A3.4 includes a second criterion for sufficient daylight that can be used alternatively to the daylight factor. This criterion solely demands a specific ratio of window to floor area. This second criterion may indicate sufficiency of daylight even in the case of a window which is heavily obstructed by a lightwell.
In order to eliminate this factually unjustified assessment a proposal to limit the scope of application of the criterion on window to floor area ratio was worked out.

Please download the complete report "Determination of criteria for lightwells to distribute sufficient daylight into workspaces" (in German only).