When it comes to exterior lighting in new nonresidential projects, there’s more to consider than just energy usage. CALGreen Section 5.106.8 outlines the requirements for all new exterior lighting associated with nonresidential spaces, and this primarily includes the maximum BUG ratings for these types of fixtures. But what is a BUG rating?
BUG is short for Backlight, Uplight, and Glare. Backlight is the area of light which illuminates the area behind the main direction of the fixture; Uplight is the area of light directly above the fixture; and Glare (sometimes known as Forward Light) is the brightness of the light. CALGreen places restrictions on these factors in order for developers to provide sufficient lighting to exterior areas, while protecting “dark skies”, minimizing uncomfortable glare, and reducing energy consumption.
BUG ratings are typically found on the product data sheets for light fixtures. To know which ratings are allowed in your project’s location, CALGreen provides a table to help identify these limits. Table 5.106.8 indicates the Lighting Zones and their respective BUG rating limits. Lighting Zones are defined by the CEC based on lighting density and usage, and they are as follows:
- Lighting Zone 1: Recreation areas and wildlife preserves
- Lighting Zone 2: Rural areas
- Lighting Zone 3: Urban areas
- Lighting Zone 4: Special use districts that may be created by a local government
Once you know the Lighting Zone for your project, you can easily identify the maximum BUG ratings for your exterior light fixtures. Note that some light fixtures may automatically comply with certain BUG ratings if they are supplemented with shades or covers to shield the light from penetrating various angles. Dark Sky lighting is an example of this type of qualifying product.
For further CALGreen and Energy Code consultation, contact Moe Fakih below:
Moe Fakih, Principal
Contributing Writer: Burke Boydell, LEED AP Homes
Photo Source with Permission – Wikipedia “Light pollution”