One of the biggest questions involved with purchasing lights for your industrial or commercial space is how many are needed. If you just want to replace your existing fixtures with their LED equivalents, we have a post to help you do that. If you want lights for a new build, or if you want to improve your current lighting layout, figuring out what’s needed is a different process altogether. Here, you’ll learn how to figure out what’s needed and/or create your own lighting layout.
The first question that needs to be answered is how much light is required in your space. The answer can be found in a document published by the Illuminating Engineering Society (IES). In their Lighting Handbook, the IES has an extensive list of suggested lighting levels for commercial and industrial spaces, such as warehouses, retail and auto shops, and parking areas. They work to inform the public of the best lighting practices to meet visual and aesthetic needs. As stated on their website, the IES is “. . . an accredited Standards Development Organization (SDO) under American National Standards Institute (ANSI) approved procedures.” The organization consists of different types of lighting professionals who are all working toward quality lighting design for every space.
The list shown below includes IES recommended lighting levels for a selection of industrial/commercial spaces. It gives these recommendations in the form of average foot-candles and lux values. Both of these are measurements for how much light makes it onto a surface. Lux means lumens per square meter, and foot-candles means lumens per square foot. A lumen is simply a measurement that describes the amount of light produced by a bulb or fixture.
Using the list, you’ll see that an office would need an average of 40 foot-candles or 40 lumens per square foot. This is not to say that the office should meet the 40-foot-candle suggestion across every inch. In some areas, foot-candles will be higher than 40, and in other areas, it will be lower, but it will average out at 40. You’d need a fixture or multiple fixtures combined that will give you about 40 lumens of light per square foot. The goal is for your space to be evenly lit with enough light everywhere that you need it.
Now that you’ve seen the IES list, it’s time to figure out approximately how many fixtures you’ll need. A graphic like the Illumination Diagram shown below can be found on LM-79 reports and photometric PDF files on our product information pages. These diagrams show foot-candles and lux produced by a fixture when mounted at different ceiling heights. They also show beam distance, which is the area covered by the light from the point of 50 percent intensity on both sides. Beams are brightest in their centers and fade as light spreads outward. Beam distance can change based on surface/wall reflectivity.
Ultimately, what’s most important in these cones is foot-candles at different heights. This allows you to find your ceiling height and quickly tell if a fixture can emit what you need. Once you know what fixture is capable of this, it’s time to do some critical thinking and take a common-sense approach to your lighting design.
Take an auto shop for example. Say this shop is 50-by-64 feet wide—so 3,200 square feet—and has a 16′ ceiling. From the IES chart above, you can see that service shops should have an average of 50 foot-candles. For a quick way to figure out how many or even which fixtures would be best, you’ll do some simple calculations using information from the light that matches your foot-candle goal. Our 300-watt UFO LED High-Bay Light meets the 50 foot-candle suggestion, so we’ll use it for this example. Multiply the shop’s square footage by the suggested foot-candle requirement and then divide that number by the fixture’s lumen output. This gives you the total number of fixtures that are ideal for your space. The formula would look like this: 3,200 x 50 = 160,000; 160,000/39,000 = 4.1. You would need 4 300-watt fixtures to light the shop.
Now is where the thinking comes in. Imagine 4 lights in your 3,200-square-foot shop.
Consider that light spreads and gets dimmer the farther away it gets from its source. Directly under the fixture will be the brightest. We know that right below these fixtures, the 50 foot-candle suggestion will be met, but as light spreads, you’re getting less and less light. So now the question is are 4 of these fixtures enough to not only give you the light you need everywhere but to achieve an ideal, symmetrical layout. Think about all the areas that need light. Will they be properly lit? While, ultimately, it’s based on personal preference, you’ll find that 4 lights is not an ideal number for that size and type of space.
So what now? To achieve a better layout with more lights to evenly cover your space, use the 300-watt fixture’s wattage to see what other fixture might be a better alternative. Our 150-watt UFO LED High-Bay Light, for example, is half the wattage and intensity, so you can double the amount of fixtures you’d need to achieve a better lighting design and improve coverage. Now you have to use your imagination again. Picture 8 lights laid out in a couple of different ways.
You might find that adding a ninth fixture allows you to have the best possible lighting layout and the most evenly lit space.
With a couple of easy calculations, you’re able to determine how to light your space. While these calculations and using your imagination can give you a good idea what you’ll need, there are certain factors that play into how your lighting will appear. The color of your walls and floor, tasks being completed, and light lost over time are some of the things that can affect how a space is lit. To get a more accurate estimate for the number of lights you’ll need, you can call one of our commercial account representatives. These representatives use lighting design programs and go a bit more in depth with you to account for different factors that might affect your lighting. If you’re content doing it on your own, the tools in this post should give you what’s needed to create a lighting design that fits your space.
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