Light conditions and window position

When striving for net zero buildings one of the important challenges is to reduce the energy consumption due to artificial lighting. Buildings have to be designed to utilize natural daylight as a replacement for artificial lighting. In order to do so window type and position are important factors that have to be considered.

The lighting software Relux makes is possible to predict how light from windows will be distributed throughout a room. The software calculates light distribution based on parameters such as location, sky conditions, room size, window size, window placement, reflectivity of surfaces etc. It turns out that how the window is placed very much determines how well the light is spread throughout the room. Just look at these three illustrations.








All the illustrations represent an office room located in Chicago. The simulations are set to represent cloudy weather, June 1st at noon. Besides positioning of the window all other parameter are the same.

The first illustration represents a window placed in a high position, close to the ceiling. The second represents a window placed on the middle of the wall and the last one represents a window placed close to the floor. We clearly see that windows placed on the upper part of the wall are much more capable of distributing light deep into the room.  This means that allowing for windows to go all the way to the ceiling can potentially reduce the need for artificial lighting. 


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