Hello!
The questions refer to a new office buiding according to LEED v4 version.
The building which is situated in a LZ2 area and the lighting boundaries are very close to the building facades (2.5-3.0m). For facade lighting we use minimum wattage light fittings and only downlighting in order to get the light pollution credit. Does the lighting boundary calculation surface refers only to direct lighting calculations or does it includes the reflected light as well?
Also, regarding the BUG rating method and referring to the document saying “Orient all luminaires less than two mounting heights from the lighting boundary such that the backlight points toward the nearest lighting boundary line”. We have the following querries:
- If the Luminaires are mounted on the building more than two mounting heights are included in the backlight calculations?
- The luminaires that are intended external areas are they evaluated according to G2 (i.e. for LZ2)? What about Backlight
Thank you
Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
734 thumbs up
July 24, 2023 - 8:38 am
The default setting for most lighting calculation software has interior lighting including direct and indirect light while exterior only includes direct light. I would just use the default settings for the software you are using.
The calculation method and the BUG rating method are 2 separate ways to document compliance. You aren't doing calculations if you are using the BUG ratings.
Wall mounted luminaires don't use backlight values. The table in this credit only lists glare ratings for building mounted luminaires. If greater than 2 hounting heights, then G2 is the max in LZ2.
Pole mounted lights you have to worry about glare and backlight. These are the lights that need to be oriented away from the boundary if they are less than 2 MH from the boundary.