How many light fittings a room needs LUX
The utilisation factor can be under a third in a tall dark room and over two thirds in a low white one. A design that ignores it is out by a factor of two.
The room
The working plane is the height the light has to arrive at: 0.85 m for a desk, 0.0 for a floor, higher for a bench. The mounting height the room index uses is measured from there, not from the floor.
The fitting, and the two factors
The utilisation factor comes from the fitting’s own table, read against the room index and the reflectances of the ceiling, walls and floor. The target illuminance comes from the table for the task. Neither is invented here.
The layout
Step by step
The working
How it works
LUX works out how many light fittings a room needs to reach a target light level. It uses the utilisation factor, which can vary from under a third in a tall dark room to over two thirds in a low white one, and designs for a room as it will be once dirty. It gives the number of fittings and checks the spacing against the mounting height. The figures stay in this tab.
Doing this often? Foundry, the Engineering Suite's drawing half draws the room and the fittings to scale, with dimensions and blocks, and prints a PDF to scale. On its own, US$4 a month; with everything else, US$9 a month or US$79 a year. 7 days free.