There are several methods to predict daylighting in buildings. The following is based on a procedure adopted by the Illuminating Engineering Society, which was developed under the sponsorship of the Libbey Owens Ford Company. It is often referred to as the Lumen Method.
This prediction method makes the following assumptions:
1. Illumination is calculated for three points in a room, all on the center line of the window: one 5 feet from the window, one 5 feet from the back wall, and one in the midpoint of the room.
2. The prediction points and the windowsill are 30 inches above the floor.
3. The top of the window extends to the ceiling.
4. No account is made for reflections from neighboring buildings.
5. The windows are vertical ...