By Craig DiLouie, LC
Lighting is both art and engineering. When a building is built, the lighting designer evaluates how the space will be used, determines the amount of light required for prevailing tasks, and specifies luminaires that will produce an appropriate amount of light output. The lighting designer will also look at where light is placed, visual comfort at all viewing angles, the appearance of visible luminaires and other aspects.
A majority of homeowners acquire homes with permanently installed lighting already in place. After that, they have two choices. They typically supplement the general lighting with portable task lighting where needed. And they may decide to replace or add luminaires.
How Much Kitchen Lighting Is Needed?
First, list the main activities that will be performed in each room. In a kitchen, activities might include food preparation, difficult reading, walking around and eating.
Second, identify the amount of light needed on the task itself for it to be properly visible. In the United States, light level is measured in footcandles. Here’s a chart showing a sample of home spaces and activities with IES-recommended horizontal light levels. These light levels are considered minimums. More light can be added where needed based on factors such as user age.
||Light Level (Footcandles)
|Kitchen general lighting (on floor)
|Kitchen food preparation (on counter)
|Kitchen sink (on top of sink)
|Kitchen cooktop (on cooking surface)
|Dining (on tabletop)
|Hallway general lighting (on floor)
|Desk (on desktop)
|Living room general lighting (on floor)
Third, identify the amount of light the lamps will need to produce the needed light level. Light output is measured in lumens.
For example, suppose our kitchen is 10 ft. x 12 ft., which represents an area of 10 x 12 = 120 square feet. For general lighting, we will illuminate it to at least 5 footcandles. A footcandle is 1 lumen/square foot, so in this case, we would need 120 (area) x 5 (footcandles) = 600 lumens from the general lighting, while the food prep area, sink and cooktop would have dedicated task lighting. The general lighting could be put on a dimmer-switch to adjust light levels to mood or function.
If you know roughly how many lamps are in each luminaire to be used, and therefore know roughly what the light output per luminaire will be, you can calculate number of lights required:
Number of Luminaires = [Footcandle Target x Room Area] / Lumens per Luminaire
If the target light level in our example 120-sq.ft. kitchen is 5 footcandles, and we will be using a luminaire that produces about 900 lumens, then we would need (5 x 120) / 900 = 0.67 or 1 luminaire.
In my next post, we’ll talk about adjusting that luminaire count based on a light loss factor called coefficient of utilization. This rather-technical sounding term refers to light lost based on room size, dimensions and finishes.
What you need to know about how much kitchen lighting you need:
- A primary aspect of lighting design is determining light level
- A simplified version of the process provides an approach for homeowners