Forum discussion
NC-v4 SSc6: Light pollution reduction
Hello,
We are considering having the exterior lighting on daylight sensor and also on a management program.
What time is considered to be "nighttime" where light pollution shall be avoided ? Can we have more luminance before this time and less after and then comply with this credit ?
For example at the end of the day (5-7pm) we are much more LUX than after 10pm. And at night we stick with the maximum allowed per this credit.
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Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
731 thumbs up
November 7, 2017 - 1:24 pm
Generally, "nighttime" is from 12am to 6am. But business hours can affect this.
What you are describing doesn't sound any different than the required controls. The luminance limits for this credit are not affected.
ASHRAE 90.1-2010.
9.4.1.7 Exterior Lighting Control
a. Lighting shall be controlled by a device that automatically turns off the lighting when sufficient daylight is available.
b. All building facade and landscape lighting shall be automatically shut off between midnight or business closing, whichever is later, and 6am or business opening, whichever comes first, or between times established by the authority having jurisdiction.
c. Lighting not specified in section 'b' above, including advertising signage, shall be controlled by a device that automatically reduces the connected lighting power by at least 30% for at least one of the following conditions
1. from 12 midnight or within one (1) hom of the end of business operations, whichever is later, until 6 a.m. or business opening, whichever is earlier; or
2. during any period when no activity has been detected for a time of no longer than 15 minutes.
Marilou Communeau
November 8, 2017 - 3:42 am
Thank you very much for your answer.
What do you mean by saying "the luminance limits for this credit are not affected" ?
Can we lighten upwards, and a litlle bit brighter before 12am ? Or the lighting needs to meet this credit requirement at any time?
Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
731 thumbs up
November 8, 2017 - 10:27 am
The luminance limits in this credit, either using the BUG method or by calculation, is based on a worst case situation. What is the brightest level of light possible. If this brightest level occurs at 7pm or 10pm doesn't matter.
- If there are security lights that are installed and only used on rare occations, these must be included too.
- If lights are installed to function at 100% output from 5-7pm then at reduced by 50% at 10pm and are off at midnight, the light output at 100% is what gets used.
- If two different lighting systems are installed, and both are never turned on at the same time, then the lights which are brightest (worst case) are used for this credit. Maybe the uplight is worst for one system and the spill light is worst for the other.