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Interior and exterior lighting
Addressing both interior and exterior lighting, this credit seeks to reduce light pollution that can block our view of the night sky and cause human health problems as well as ecological problems for many birds, insects, and other animals. Light pollution often represents nighttime lighting that isn’t needed, wasting energy while causing light trespass and contrast, reducing visibility.
Better lighting = Better safety, less energy
Many people think that more lighting means better nighttime safety and security. However, too much exterior...
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5 Comments
SSC8 Lamp Lumen Calculation
I am in process of performing a lamp lumen1. A lumen is a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of 1 candle intensity. 2. A measurement of light output. calculation as part of my submittal documentation. Can any one tell me what lumen value we should be using for the Initial Fixture Lumens per liminaire? Is this the Initial lumens as identified for the lamp that the fixture utilizes?
Bill Swanson replied May 26 2010
I don't think it matters. As long as you're consistent with all fixtures on the site.
The credit reads "initial fixture lumens". If you want to calculate it out that way then you're meeting the letter of the credit. But most people just use initial lamp lumens. It's faster than looking up the efficiencies of each fixture. And if metal halide fixture 'A' is 80% efficient and metal halide fixture 'B' is 78% efficient, it's not going to matter much. The ratio of up and down light will be near identical for fixture lumens and lamp lumens.
If you don't know what I'm talking about then a lamp puts out X lumens. The fixture we put the lamp in bounces the light around but not all of it gets out. Some stays trapped inside of the fixture. The amount of light that gets out compared to the bare lamp lumens is called the fixture efficiency.
1000 lumen lamp put into a fixture and the fixture puts out 800 lumens means the fixture has an 80% efficiency. Most cutsheets will say what the efficiency is if you look hard enough.
Bill Swanson replied May 26 2010
LED lights will not have an efficiency. If they are tested per LM-79 the listed lumen1. A lumen is a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of 1 candle intensity. 2. A measurement of light output. value is the fixture lumen value.
security wall packs on building facade
Are security wall packs on building facades considered architectural facade lighting? In other words, do wall packs need to be considered in the calculations of exterior lighting (even if they are full cut off fixtures?)
Bill Swanson replied Jul 14 2010
Yes, they need to be considered in the exterior lighting calculations. Per USGBC's CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide response. I think the second paragraph is what you're looking for.
Question:
The firm that will occupy this office building works on many projects of a sensitive nature so security is a significant concern, both for employees arriving early or working after dark and for protection of the facility from intrusion.
Is it acceptable to include motion-sensor activated lights that do not fall within the allowable site lighting wattage? These lights would be located in the immediate vicinity of the building and would only be enabled to turn on when other site lights are off. They would only remain on for a limited time following activation.
If such motion-sensor activated lights are allowed, can they be excluded from the other requirements of this credit, property line illuminance and uplight components, since their purpose is only safety and security?
5/6/2009 - Ruling
The applicant is requesting confirmation if it is acceptable to exceed the lighting power density requirements with motion responsive after‐hours security lighting that is only enabled when the other site lighting is off. Based on the description provided, this strategy is only acceptable provided that when the security lighting is ON, the combined security and general lighting that remains ON, does not exceed the lighting power density thresholds and the security lighting is capable of being controlled to prevent simultaneous operation with the offsetting exterior luminaires.
The second question asks if the lights can be excluded from the other requirements of SSc8 and the answer is no. These luminaires must meet the light trespass requirements relative to their declared environmental zone at the applicable site boundary, as well as the sky glowSky glow is caused by stray light from unshielded light sources and light reflecting off surfaces that then enter the atmosphere and illuminate and reflect off dust, debris, and water vapor. Sky glow can substantially limit observation of the night sky, compromise astronomical research, and adversely affect nocturnal environments. requirements of the credit.
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