Areas experiencing light pollution due to excessive and unwanted light distribution can negatively affect humans, wildlife, and the environment. Combat the risk of light pollution by paying attention to a light’s BUG Rating. Keep reading this blog to learn more about what BUG Ratings are, how to calculate them for various fixtures, and why you should care about the effects of higher BUG Ratings and light pollution.
What Are BUG Ratings?
The Illuminating Engineering Society (IES) and DarkSky International created the BUG Ratings in 2009, replacing the outdated cutoff system to reduce light pollution and light trespass caused by outdoor light fixtures. The BUG ratings depend on a fixture’s backlight, uplight, and glare.
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Backlight refers to light trespass displayed behind a light fixture. This can affect homes if outdoor lights are reflecting light back into windows.
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Uplight is when there is light spread above the fixture. This creates light pollution, making it difficult to see the stars in the night sky, and affecting wildlife.
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Glare occurs when excessive bright light is in unwanted areas, impacting visibility and causing eye strain. This can create safety risks for pedestrians, specifically when driving.
BUG Rating Scales
A fixture's BUG Rating depends on the zonal lumens emitted in the backlight, uplight, and glare secondary solid angles.
We list the subzones for each category below.
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Backlight subzones are related to light trespass, which refers to unwanted light spreading onto other properties. The ratings are broken into backlight very high (BVH), backlight high (BH), backlight mid (BM), and backlight low (BL).
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Uplight subzones are related to skyglow, which refers to artificial light directed upward, reducing the visibility of the night sky. The ratings include uplight high (UH) and uplight low (UL).
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Glare subzones are also related to light trespass, which can cause visual discomfort. The ratings are divided into two categories for asymmetrical or symmetrical fixtures. Both categories have four zones: forward light very high (FVH), forward light high (FH), backlight very high (BVH), and backlight high (BH).
Considerations:
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The BH zone is used in both backlight and glare calculations, but the BVH zone is used exclusively in glare calculations.
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The forward light mid and forward light low zones don't count towards the BUG Rating because they distribute light 0-60 degrees off the ground and are considered useful light from the fixture by design.
We review the specifications of the different backlight, uplight, and glare ratings below.
How to Calculate BUG Ratings
The charts below show the maximum lumen requirements for each backlight, uplight, and glare rating.
How do I use these charts?
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Once you have the fixture you’re measuring, examine the photometric data to determine the lumen value at each section. To do this, you need to use the lowest lumen rating of the secondary solid angles to find the value where it doesn’t surpass the category’s maximum lumens. For example, a BH zone with 700 lumens would fall under the B2 category.
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Use the highest rating for the category. For example, if you're calculating your overall backlight rating and you have a B1 rating for BH, B2 for BM, and B1 for BL, the overall rating would be B2.
However, to save you from manually calculating the rating every time, you can typically find the BUG Ratings for our fixtures under our product specifications table. We have an image of the product specifications for one of our Amber LED Turtle-Friendly Parking Lot Lights below for reference.
Why Should I Care About BUG Ratings and Light Pollution?
Light pollution can severely impact humans, wildlife, and the environment.
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Humans: Outdoor lights with a high BUG Rating can cause light trespass through windows, disrupting sleep and natural circadian rhythms.
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Wildlife: Many animals rely on the night sky and stars to navigate, and artificial lighting can distort them and cause them to get lost, putting them at a greater risk of predators. The light also exposes nocturnal animals that are active at night.
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Environment: Excessive, unneeded light leads to energy waste and increased carbon footprint. It also raises electricity costs for the individuals or businesses powering these lights.
Many cities and states have local ordinances, some following the DarkSky organization’s guidelines, to encourage light pollution reduction.
For more information on reducing light pollution, check out this blog, or for more information on the adverse effects of light pollution on wildlife, read here.
What Fixtures Have the BUG Rating I Need?
The closer a BUG Rating is to 0, the better. Our turtle-friendly parking lot lights and wall packs have lower BUG ratings, such as B2-U2-G1 and B3-U0-G3. However, some of our regular parking lot lights and wall packs have low BUG ratings, such as B3-U0-G3 and B2-U0-G1.
The BUG rating used might vary based on the area's Lighting Zone. There are five zones, where darkness is most important in the lower zones.
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LZ0: Areas where no overhead light is needed, such as national reserves.
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LZ1: Areas where very low overhead lighting should be used, such as national parks and city parks.
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LZ2: Areas where average overhead lighting is needed, typically in more urban areas such as around schools and residential subdivisions.
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LZ3: Areas needing slightly higher lighting levels, usually in shopping centers and gas stations.
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LZ4: Areas requiring high light levels, not a very common zone, but could include highly dense business districts.
For example, you’d typically use luminaires in an LZ0 or LZ1 area with 0 or 1 BUG Ratings, whereas in an LZ4 area, you’d be okay with a higher rating of 3+.
Get Started
Understanding the importance of BUG Lighting Ratings and the effects of poorly directed light on the environment can reduce light pollution while providing the necessary light for visibility and safety. If you’re ready to upgrade your outdoor light fixtures or find lighting for a new application, start with Super Bright LEDs today. Our knowledgeable team of customer service advocates and product support specialists can help answer your product questions or assist you in choosing the correct fixture for your application. Contact us today at 866-590-3533 or fill out this contact form.
