Office lighting is more complicated than one may think at first glance. It needs to do the obvious, provide lighting, but it should also accomplish several other tasks as well. Properly designed office lighting provides visual comfort, enhances worker performance, and helps keep employees safe. And, in addition to doing these things, if you use LEDs, in a well-planned manner, good lighting can also reduce a building owner’s operating costs. How do you accomplish this, you may be wondering… Just read on to find out.
Illuminance on Walls & Ceilings
In the same way that the illuminance of a task area is important, the illuminance of the surfaces that surround it also has a significant impact on visual comfort. Generally, for an office setting, we recommend that the illuminance values for walls be around 50 lux and illuminance for ceilings as 30 lux. In addition to this uniformity needs to be equal to or higher than 0.10. Typically, the higher the illuminance levels of the ceilings and walls, the more comfortable people will be.
Although it may have once been acceptable to decide how many lumens you wanted and then space fixtures around the room to achieve the desired light levels, that’s no longer the case. Modern offices have distinct areas that require different levels of lighting. And, thanks to the introduction of computers, there’s glare to be concerned about as well.
Non-uniform lighting allows people to create customized lighting for the area depending on the intended usage and helps to save on power bills by reducing energy consumption. You can plan for all of this easily with our free photometric lighting plan , but we’ll also outline how you can estimate it yourself, below.
The Lumen Method
The lumen method is based on the definition of a footcandle, or as we mentionned above, the lumens on a surface area of 1 sq ft on which there is a uniformly distributed flux of one lumen. This is expressed in the equation below:
E = Lu ÷ A
where E is the average illuminance in fc, Lu is the number of lumens, and A is the area in sq ft.
Using the number of fixtures in an area, the number and types of bulbs installed in each light, you can calculate the total lumens generated by the lamps by multiplying the total initial lamp lumens by the initial lumens per lamp. But, this number isn’t entirely accurate. Not all lumens reach the floor, and therefore not all lumens are applicable. In order to account for this, you’ll need to find a factor that represents the ratio between the lumens reaching the work plane and the total lamp lumens produced. This is known as the coefficient of utilization (CU).