Schools-2009 SSc8: Light Pollution Reduction

  • Schools-2009 SSc8 Light Pollution Reduction- Credit Requirement

  • 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.

    SSc8 YouTube video

    Better lighting = Better safety, less energy

    Many people think that more lighting means better nighttime safety and security. However, too much exterior lighting can make outdoor and parking areas less safe by creating high contrast between lit and unlit spaces. Among other problems, when the human eye is flooded by bright light, it becomes harder to adjust to darker areas and shadows. Too much exterior lighting also means unnecessary energy consumption. Some objectives to keep in mind when striving for safe, efficient, and aesthetically pleasing lighting design are lighting uniformity, low contrast, no glare, and preventing light from spilling off the site. This can be achieved through judicious selection of fixtures with full cutoffA full cutoff luminaire has zero candela intensity at an angle of 90 degrees above the vertical axis (nadir or straight down) and at all angles greater than 90 degrees from straight down. Additionally, the candela per 1,000 lamp lumens does not numerically exceed 100 (10%) at an angle of 80 degrees above nadir. This applies to all lateral angles around the luminaire. that direct light toward the ground but prevent it from shining up into the night sky.

    Full-cutoff luminaires reduce light pollution, improving views of the night sky.

    The four requirements can make it complicated

    This credit has four separate requirements, which can make compliance complicated—though not necessarily difficult. One addresses indoor lighting spilling to the outdoors, and three deal with exterior lighting, including façade lighting, site lighting of areas like pathways and parking lots. In most circumstances, these requirements are relatively easy and cost-neutral to meet. The biggest challenge often comes in dealing with light-trespass limits—light bleeding off the project site into a neighboring site—on projects with small or constrained sites. You will also need to attain low lighting power densities per ASHRAE 90.1-2007, which is a good general practice and won’t require you to compromise on aesthetics or cost.

    LEED boundary is important

    You’ll need to pay careful attention to establishing a LEED project boundary, which plays an important part in meeting light trespass requirements. Involve an exterior lighting designer (or landscape architect) early in the design process to develop photometric plans and guide fixture selection during design.

    FAQs for SSc8

    Are residential spaces exempt from the interior lighting calculations?

    Yes, as of 4/1/12 per LEED for Homes 2008 Interpretation #10147, “residential spaces (dwelling units only) within the scope of other LEED projects are also exempt from the interior lighting requirements.”

    Do existing fixtures need to be included in the exterior lighting calculations?

    Yes, if they are within the LEED project boundary.

    Can the Application Guide for Multiple Buildings and On-Campus Building Projects be used for the exterior lighting requirements?

    Yes, as long as the entire site meets the requirements.

    Can a mix of Option 1 (opaque surfaces) and Option 2 (automatic controls) be used to meet the interior lighting requirements?

    Yes.

    Are hospitals exempt from interior lighting requirements?

    No, hospitals are not exempt from the interior lighting requirements.

    What effect did the November 2011 ASHRAE table 9.4.6 Addendum i have on exterior lighting power allowances?

    Significant reductions for tradable surfaces in LZ1 and LZ2 and some in LZ3. See the new table for details. It also added lighting power allowances according to light zones, removed a 5% adder, and introduced a base site allowance. Suggest revising response and adding a link to the Addendum i available for free download on ASHRAE website.

    What about zero lot line projects, where is the boundary?

    You can use the curb line.

    To calculate building façade lighting power density, how do you determine the area used in the calculation?

    Use only the area that has measurable light on the surface; baseline and proposed are the same.

    Where are vertical footcandles measured at the site boundary?

    At grade level.

    Is signage included in the LPD calculations for building façades?

    No, per ASHRAE table 9.4.5, you can exclude lights in display windows, advertising, and directional signs as long as they are switched separately from other lighting.

    Does uplight that is under a canopy count towards the limitation of total initial design fixture lumens at 90 degrees or higher from nadir?

    If the canopy blocks 100% of the light then yes, but this is unlikely. Any light spillage needs to be counted toward the uplighting limit, but calculating this can be difficult. Using downlights is recommended instead.

    Is flag lighting exempt from this credit?

    Not currently, but USGBC is looking at exempting flag lighting from LEED v4 requirements.

    Are city-owned lights within a project's property required to comply with credit requirements?

    According to LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #10236, street lighting that is required by the governmental authorities to be installed within the LEED project’s lighting boundary (whether existing or new) does not need to be included in any of the calculations.

    For campus projects, do all existing light fixtures need to comply with credit requirements at the time of a project's submittal?

    All existing fixtures within the LEED project boundary would need to comply with the SSc8 requirements at the time the project is submitted for review. However, if the project elected to use the campus property boundary as the "lighting boundary" for SSc8 as allowed by LEED Interpretation #10236, existing fixtures within the lighting boundary, but outside the specific LEED project boundary would not have to comply with any of the SSc8 requirements. Essentially, the "lighting boundary" is only used in such circumstances for evaluating that the light trespass requirements are met at that boundary by lighting located within the LEED project boundary.

    What advertising lights or signs must comply with credit requirements and which are exempt?

    Advertising and directional signage, as explained in Addendum i of ASHRAE 90.1-2007, and further defined in the Users Manual for ASHRAE 90.1-2007, is exempt.  Essentially, that means that internally illuminated advertising signs are exempt, but those illuminated by lighting that is not ‘integral’ to the signage itself must be included in the calculations.

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

Expand All

  • Designate one responsible party to oversee exterior lighting-related LEED credit requirements. For large projects, this person may be the civil engineer or landscape architect. For small projects it may be the architect, lighting designer, or other relevant team member.

  • Identify the building owner’s goals for occupant safety and comfort as well as for architectural lighting, including façade lighting. Include these goals in the Owners Project Requirements for EAp1: Fundamental Commissioning. 

  • One of the biggest barriers to reducing light pollution is the cultural and aesthetic affinity for brightly lit buildings. Owners can play an important leadership role in contending with these expectations, establishing aesthetic goals that do not include excess lighting for purely aesthetic purposes. The design team can play an important role by maintaining low levels of lighting and highlighting specific façade architectural features with focused, low intensity lights.

  • Projects that demand brightly lit facades and entrances, such as casinos, hotels, theatres and commercial complexes, may have a hard time reconciling these desires with the requirements of this credit. Deliberate lighting design can forge a compromise between the desire to emphasize the building facades and the need to eliminate light pollution in order to meet the credit requirements.

  • Identify the urban lighting zone as defined by IESNA RP-33, based on the population density of the neighborhood, in order to establish lighting requirements.

  • Finalize the LEED project boundary in coordination with other LEED credits. The responsible party and the project team should identify the lighting fixtures close to the boundary that will be part of the lighting trespass analysis.

  • Projects with a zero lot line may choose to use the curb as the LEED boundary for the purposes of documenting light trespass only, while using the site boundary for other credits. This is one of the few exceptions to the rule that the LEED boundary and corresponding site area be consistent across multiple credits. Sites that abut public rights of way may similarly use the curb to establish the site boundary for the purposes of LEED documentation. It can be challenging for projects with zero lot lines or with little open space to meet the maximum exterior illuminance requirement of 0.1 footcandles at the site boundary. Project teams are only responsible for lights that are part of their project. For example, municipal lights about which the project has no control do not need to be considered. 

  • Campus projects can choose whether to comply with the requirements for the building site boundary or to meet the light trespass requirements for the campus as a whole. For a project on a campus, choosing to meet the light trespass requirements at the building level can be very difficult.

  • Identify local or regional lighting laws or required lighting levels for rights-of-way that may apply to the project site. These regulations may help teams identify areas to focus on when dealing with lighting trespass in the design.

  • Discuss fixture and lamp options with the landscape designer, civil engineer and other project team members, focusing on both reducing overall lighting power density, and on avoiding light trespass. Avoiding light fixtures that shine up into the sky is the easiest way to reduce light pollution and make better use of lighting. This can be done by eliminating exterior lighting entirely or by selecting “cut-off fixtures” with opaque covers that direct light downward.

  • Local or regional laws that regulate lighting levels typically do not require minimum input power in watts. Going beyond these local requirements by selecting energy-efficient fixtures can help your project meet codes for comfort and safety goals without compromising energy efficiency.

  • The credit requires a photometric study on site lighting that may add minor consultant costs but will add value by optimizing the design.

  • Optimizing lighting can eliminate unnecessary costs for extra lights and high-power fixtures.

  • Many smaller fixtures may make for a better layout than fewer high-wattage ones. The designer should be able to advise about additional infrastructure costs associated with an atypical lighting design. Low power density and light intensity may require higher first costs for fixtures that will save electricity costs during operations.

  • Rebates and incentives on the federal, state, and local levels are available for low-power and Energy Star lamps.

  • Safety concerns are not typically a valid excuse for higher exterior lighting allowances. Despite a perception of better safety with brighter lighting, floodlights can often create areas of deep shadow, and the high contrast can be difficult for the human eye to navigate. Use good design, downlights, and work with the owner to address any concerns.

Schematic Design

Expand All

  • Interior lighting

  • Be aware of all requirements for interior lights so that fixtures do not direct light through windows to the outdoors. Identify locations where fixtures might have a direct line of sight to a window or other opening. The lighting designer should either eliminate those fixtures from the design, provide shades to prevent more than 10% of light from shining outdoors, or include controls to reduce the input power by 50% between 11 p.m. and 5 a.m.

  • Interior lighting cannot spill out of the windows after business hours, defined as 11 p.m. – 5 a.m. in the credit requirements. Window coverings or automatic controls like timers, occupancy sensors, or master switches have to shut off or reduce the input power by 50% for all non-emergency indoor lights during that time.

  • Fixtures that throw 50% or more of the cone of light out a window are likely to present problems.

  • To avoid letting this credit slip through the cracks, project owners or architects should ask the lighting designers at the outset of the project how they plan to achieve each aspect of the credit.

  • Additional light controls and automatic window screens may add to construction costs, but controls can reduce electricity consumption.

  • Exterior lighting

  • Identify the project location and IESNA-designated zone to determine the threshold for exterior lighting levels.  Utilize resources like the website www.citydata.com to identify relevant population density and appropriate designation.

  • The lighting designer includes the design intent in Basis of Design for EAp1: Fundamental Commissioning, for all outside lighting requirements, listing minimum illuminance in footcandles, lumens, or candela for all spaces with controls, fixture requirements and design approach.

  • The lighting designer then develops the exterior lighting layout and selects fixtures that optimize light with low power use.

  • Nadir illustratedTo determine the total power density for the project, the lighting designer tabulates all exterior space and identifies the wattage of selected fixtures to compare it with the LPD allowable by ASHRAE 90.1-2004, Exterior Lighting Section. The selected fixtures should have full shielding or cutoff to reduce light directed toward the night sky.

  • The lighting designer develops a photometric study for exterior lighting intensity, the impact of shades and cutoff fixtures, and light trespass from the project boundary. Use the photometric study to inform any changes in the design. School projects need two sets of photometric studies, one with sports lighting only and the other without sports lighting. 

  • For schools, the playground lights must turn off automatically after 11 p.m., with manual overrides available for special occasions. When designing exterior light-fixture layout, locate light fixtures as far from site boundary as possible.

  • The key to achieving this credit is to find the optimum balance between lighting quality and lighting energy consumption. It is often assumed that more light is better, but a low level of uniform lighting throughout a site will eliminate the need to install bright halogen lamps that illuminate some areas and leave others dark in contrast.

  • Exterior lighting includes all ground lighting, all façade lighting, flag lighting, any rooftop or terrace lighting, and any other fixtures outside the building. Pay careful attention to exterior light fixtures and light levels at building entrances close to the LEED site boundary.

  • Revisit the LPD calculations to make sure any design changes maintain the threshold limits.

  • ASHRAE’s exterior lighting density table lists exterior spaces under two categories. Tradable surfaces are those where the average LPD of all those surfaces are within the total LPD limits. For example, in LZ4, both sales canopy lighting and stairway lighting have a maximum of 1.0 Watts/ft2. The project may decide to increase sales canopy lighting to 1.1 Watts/ft2 as long as the stairways compensate with a decreased LPD of 0.9 Watts/ft2 (given that the surfaces are the same area) so that the average of the two is 1.0 Watts/ft2. For non-tradable surfaces, such as bank ATMs, each space must individually comply with the ASHRAE requirements. Identify whether exterior surfaces are tradable in order to provide flexibility.

  • A photometric study will facilitate communication about lighting levels among the designer, owner and the design team. The study entails computer modeling simulating the lighting intensity of the designed layout in footcandles, lux or candela. It allows the designer to see the resulting output, with iterative design options as the fixtures are reduced or replaced. Typically the photometric study measures light levels in a 10’x10’ grid. The analysis also investigates the maximum initial illuminance value at horizontal and vertical limits on the site boundary to ensure they are within the limits of the project zone. If you find that lights are above the threshold, the designer may want to explore alternative numbers of fixtures and fixture types and present these alternatives to the owner, who makes the final decision.

  • Avoid aiming light at highly reflective site and ground surfaces, such as white pavement and water features, which can exacerbate light pollution. The photometric study may not capture these characteristics.

  • All site lighting, with the exception of sports field lighting, must meet the light trespass requirements of the neighborhood type, according to the IESNA zone categories. In addition, the sport lighting levels must be within limits listed in the LEED reference guide.

  • Some lighting manufacturers will offer to perform a photometric study of your site if your team selects their product for the project.

  • Security-oriented lighting designs such as those for prisons, parking lots, and walkways often focus too much on big, bright lamps. This can be counterproductive, creating high contrast between lit and unlit spaces, worsening visibility in both places. Use more moderate, uniform light levels for improved designs.

  • Some types of lighting are exempt from the ASHRAE limits on power density. Examples include advertisement signage, transportation signage, athletic fields, storage, and historic landmarks and other public monuments. Refer to Exceptions under ASHRAE 90.1 2004 Section 9.4.5.

  • The lighting intensity of conventional fixtures such as halogens, incandescents, and sodium halide lighting, drops off significantly after the first year of operation. LED or fluorescent fixtures will better maintain their lighting intensity at the level of the installation—contrary to the common perception that low power wattage fixtures, such as LEDs or fluorescents, have low lighting intensities.

  • Full cutoff fixtures can generally be specified at zero cost premium.

  • Cost premiums for this credit may come from the higher number of (shorter) poles and fixtures needed to achieve greater lighting uniformity.

  • New fixtures like LEDs with high lighting levels but low power density may cost more than conventional halogen fixtures, but most of the new fixtures have longer life and are less expensive to operate due to low electricity use and infrequent lamp replacement.

  • Costs for the photometric study can be decreased if manufactures agree to do their own calculations, which is common if you select their fixtures.

Design Development

Expand All

  • Come to an agreement among the owner, landscape designer and lighting designer about the appropriate lighting levels and site lighting distribution.

  • Demonstrate to the owner the project team’s decision about lighting levels for the final design. Owners may need to be shown similarly lit areas to understand the implications of a shift from a brightly lit façade and terrace.

  • Locally mandated lighting levels for exterior fixtures higher than LEED-mandated ASHRAE levels have been a stumbling block for credit compliance, but with proper documentation supported by a clear narrative, this challenge can be overcome. There is an option to not include those fixtures in the LPD calculations and light trespass requirement, but you must demonstrate that these fixtures are full cutoff. To document the credit, make the case that the legally mandated fixtures are beyond the control of the project. Demonstrate that the project has met the requirements with rest of the lighting. Provide a detailed photometric plan, the municipal regulations, and a narrative describing how the project has achieved all requirements of the credit except where the municipal regulations overrule it.

Construction Documents

Expand All

  • Confirm all the lighting fixtures are listed on the lighting plan. This ensures that the correct components are purchased and installed to maintain the credit requirements.

  • The designer reviews the final bid documents and budget estimates to confirm that the fixtures have not been substituted for by another type, and that interior lighting controls and window shades are not omitted. 

  • If your team undertakes a value engineering process, make sure the full cutoff fixtures are not eliminated from the list or replaced by incandescent or high-powered halogen fixtures. These changes are often overlooked and may cost the project this credit.

  • If the project is going for multi-party contractor bid, make sure the bid’s package reflects the fixture specifications and performance. Otherwise the contractor may replace the specification with a similar lower-cost fixture that doesn’t have the same wattage or a cover for cutoff.

  • Full-cutoff luminaires should not cost more than conventional fixtures, but other common strategies for meeting this credit may add costs. These include controls, timers, sensors, and  low-power lights like LEDs. Ensure that these features are not eliminated during value-engineering.       

Construction

Expand All

  • The designer should review shop drawings and visit the site for installation inspection. This ensures that the fixtures have a cut-off for uplighting, the ballasts are as specified, and the controls are all included.

  • The commissioning agent carries out the functional testing for all control sequences and timers if installed for lighting design.

Operations & Maintenance

Expand All

  • Timer controls and automatic switches should be commissioned and inspected for performance periodically throughout their life to ensure they continue to serve the intent of the credit requirements.

  • The facility manager should be involved in the decision of whether to select light timers or automated blinds to comply with interior lighting requirements. Both solutions offer opportunities and challenges during building use, depending on how the building is used and occupied.

  • Long-life, low-power lamps like fluorescents and LEDs will help keep costs low for operations and maintenance.

  • USGBC

    Excerpted from LEED 2009 for Schools New Construction and Major Renovations

    COPYRIGHT © 2009 BY THE U.S. GREEN BUILDING COUNCIL, INC. ALL RIGHTS RESERVED

    SS Credit 8: Light pollution reduction

    1 Point

    Intent

    To minimize light trespass from the building and site, reduce sky-glow to increase night sky access, improve nighttime visibility through glare reduction and reduce development impact from lighting on nocturnal environments.

    Requirements

    Project teams must comply with one of the two options for interior lighting AND the requirement for exterior lighting.

    For interior lighting

    Option 1

    Reduce the input power (by automatic device) of all nonemergency interior luminaires with a direct line of sight to any openings in the envelope (translucent or transparent) by at least 50% between 11 p.m. and 5 a.m. After-hours override may be provided by a manual or occupant-sensing device provided the override lasts no more than 30 minutes.

    OR

    Option 2

    All openings in the envelope (translucent or transparent) with a direct line of sight to any nonemergency luminaires must have shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. (controlled/closed by automatic device for a resultant transmittance of less than 10% between 11 p.m. and 5 a.m.).

    For exterior lighting

    Light areas only as required for safety and comfort. Exterior lighting power densities shall not exceed those specified in ANSI/ASHRAE/IESNA Standard 90.1-2007 with Addenda i for the documented lighting zone. Justification shall be provided for the selected lighting zone. Lighting controls for all exterior lighting shall comply with section 9.4.1.3 of ANSI/ASHRAE/IESNA Standard 90.1- 2007, without amendments1.

    Classify the project under 1 of the following zones, as defined in IESNA RP-33, and follow all the requirements for that zone:

    LZ1: Dark (developed areas within national parks, state parks, forest land and rural areas)

    Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.01 horizontal and vertical footcandlesVertical footcandles occur on a vertical surface. They can be added together arithmetically when more than 1 source provides light to the same surface. (0.1 horizontal and vertical luxMeasurement of lumens per square meter.) at the LEED project boundary and beyond. Document that 0% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).

    LZ2: Low (primarily residential zones, neighborhood business districts, light industrial areas with limited nighttime use and residential mixed-use areas)

    Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.10 horizontal and vertical footcandles (1.0 horizontal and vertical lux) at the LEED project boundary and no greater than 0.01 horizontal footcandlesHorizontal footcandles occur on a horizontal surface. They can be added together arithmetically when more than 1 source provides light to the same surface. (0.1 horizontal lux) 10 feet (3 meters) beyond the LEED project boundary. Document that no more than 2% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).

    LZ3: Medium (all other areas not included in LZ1, LZ2 or LZ4, such as commercial/ industrial, and high-density residential)

    Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.20 horizontal and vertical footcandles (2.0 horizontal and vertical lux) at the LEED project boundary and no greater than 0.01 horizontal footcandles (0.1 horizontal lux) 15 feet (4.5 meters) beyond the site. Document that no more than 5% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).

    LZ4: High2 (high-activity commercial districts in major metropolitan areas)

    Design exterior lighting so that all site and building-mounted luminaires produce a maximum initial illuminance value no greater than 0.60 horizontal and vertical footcandles (6.5 horizontal and vertical lux) at the LEED project boundary and no greater than 0.01 horizontal footcandles (0.1 horizontal lux) 15 feet (4.5 meters) beyond the site. Document that no more than 10% of the total initial designed fixture lumens (sum total of all fixtures on site) are emitted at an angle of 90 degrees or higher from nadir (straight down).

    LZ2, LZ3 and LZ4 - For LEED project boundaries that abut public rights-of-way, light trespass requirements may be met relative to the curb line instead of the LEED project boundary.

    For all zones

    Illuminance generated from a single luminaire placed at the intersection of a private vehicular driveway and public roadway accessing the site is allowed to use the centerline of the public roadway as the LEED project boundary for a length of 2 times the driveway width centered at the centerline of the driveway.

    Sports field lighting (physical education spaces)

    Physical education spaces (playing fields) do not need to comply with the lighting power density requirements of this credit, as per ANSI/ASHRAE/IESNA Standard 90.1-2007 section 9.4.5, exception E.

    Trespass calculation

    All trespass calculations must be submitted for 2 conditions: (1) with the sports lighting turned off and all other site lighting turned on, the light trespass requirements are as stated above, and (2) with just the sports lighting turned on, the light trespass requirements for horizontal and vertical footcandles (fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter.) may be increased to the following illuminance levels:

    LZ1 = 0.10 fc (1.0 lux) at the LEED project boundary, dropping to 0.01 fc (0.1 lux) within 10 feet (3 meters) of the boundary
    LZ2 = 0.30 fc (3.0 lux) at the LEED project boundary, dropping to 0.01 fc (0.1 lux) within 10 feet (3 meters) of the boundary
    LZ3 = 0.80 fc (8.0 lux) at the LEED project boundary, dropping to 0.01 fc (0.1 lux) within 15 feet (4.5 meters) of the boundary
    LZ4 = 1.50 fc (16.0 lux) at the LEED project boundary, dropping to 0.01 fc (0.1 lux) within 15 feet (4.5 meters of the boundary


    1The requirement to use ASHRAE Addenda is unique to this credit and does not obligate Project teams to use ASHRAE approved addenda for other credits.
    2 To be LZ4, the area must be so designated by an organizations with local jurisdiction, such as the local zoning authority.

    Potential Technologies & Strategies

    Adopt site lighting criteria to maintain safe light levels while avoiding off-site lighting and night sky pollution. Minimize site lighting where possible and use computer software to model the site lighting. Technologies to reduce light pollution include full cutoff luminaires, low-reflectance surfaces and low-angle spotlights.

Exterior Lighting Power Density

All Options

Perform calculations to demonstrate credit-compliance with exterior lighting power density requirements.

Compliant Light Fixtures

Refer to manufacturer cut sheets for the angle of light spilling above horizontal, the candela graph for maximum candela notation, and watts.

Intersection of Driveway and Roadway

This graphic illustrates SSc8's particular rule for how the site boundary relative to illuminance can expand when a driveway meets a public roadway.

Luminaire Schedule

The schedule lists all the exterior fixtures that will be accounted for in the the lighting power density calculations required for this credit.

Exterior Lighting Layout

Provide documentation like this example to showcase the exterior lighting layout plan. You'll refer to this plan in providing fixture and photometric analysis.

Annotated Photometric Plans

This set of annoatated photometric plans was created by Bill Swanson, P.E. for LEEDuser as a teaching tool for SSc8 documentation issues. They are not intended as examples of actual documentation, though a lot can be learned from them. These documents include a detailed plan showing a compliant site with light levels in the site and as required around the boundary, with advice and useful tips. The fixture comparison document is a means to better understand and compare the spill light from different light fixtures and placements. Think of the purple line as the edge of a cutout with a pin thru the paper where the pole is.  Move the cutout over the site when locating poles, if the cutout overlaps the line beyond the property line then that fixture cannot be located and aimed as placed. The driveway entrance example shows the impact of fixture placement around driveway entrances, and the special allowance for the site boundary around those entrances.

Design Submittal

PencilDocumentation for this credit can be part of a Design Phase submittal.

46 Comments

0
0
Tor Kyaagba Project Manager Henneman Engineering
Sep 19 2012
Guest
6 Thumbs Up

Exclude Existing Lights From Calculation?

A new building, for which LEED certification is sought, will be constructed on an elementary school campus that has multiple existing buildings. The LEED boundary is at the property line and includes all buildings on campus. Is it acceptable to include all new sight lighting but exclude all existing site lighting from the trespass calculations?

1
1
0
Bill Swanson PE, LEED AP, Integrated Architecture Sep 19 2012 LEEDuser Expert 10086 Thumbs Up

There was an old v2.1 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 that I found that is applicable to v2009 school projects.

6/15/2004 ID# 3108
"Ruling

The intent of the credit addresses a project's "building and site." The bracket-mounted lights above the secondary doorways are part of the building, and thus certainly need to meet the LEED requirements. Site/pathway lighting is not as straightforward a scenario. Applicable Internationally.

Your building project is within a university campus context and thus site lighting choices are possibly controlled by a central design plan for reasons such as security and consistent aesthetics. Granted this situation presents challenges in applying LEED-NC, but SSc8 is about delivering a specific type of lighting performance for the entire project, not for selected pieces of it. As stated in your narrative, the site definition is being applied consistently to all aspects of the LEED submission as USGBC requires.

Given the project's context, however, USGBC is willing to offer an alternative compliance path on university campuses for existing site lighting that falls within the site boundaries per the LEED application (in this case, the low pole fixtures that are not slated for replacement) IF it is shown that the Campus Exterior Lighting Master Plan (if it exists) has been officially upgraded to a SSc8-compliant level (assumably after the low pole fixtures were installed) by the time of LEED application submittal, whether or not it has been inspired by striving for this LEED point. In addition, since the "property boundary" in this case is created for administrative purposes only, defined for the project's scope (as well as LEED application), the SSc8 requirements relating to the property line need only be followed for the REAL campus property boundary, rather than the PROJECT boundary. This compromise ensures that all future site lighting installations on the campus will serve the intent of the credit and thus achieve performance beyond what would be accomplished through solely replacing the project siteÆs pole fixtures.

If no Campus Exterior Lighting Master Plan exists, or it has not been updated to comply with SSc8, then the site lighting in question must be changed to comply with SSc8 in order to achieve the credit. Look into the possibility of retrofitting (via 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. and shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. changes), or replacing the fixtures outright."

Post a Reply
0
0
Carol Liebst Design Engineer Johnson Engineering
Jul 13 2012
Guest
24 Thumbs Up

Option 1, SSc8 - automatic control between 11pm and 5am

If selecting Option 1 of SSc8, are occupancy sensors acceptable as automatic control of light fixtures? I guess what I am asking is if the lights are turned off by an occupancy sensor, under normal conditions in a school, the lights would be off due to no occupants. If the building is occupied for a special event between 11pm and 5am, is an override on permissable, or would you need to allow only 50% of the light on between these hours to be in compliance?

1
1
0
Bill Swanson PE, LEED AP, Integrated Architecture Jul 16 2012 LEEDuser Expert 10086 Thumbs Up

Generally occupancy sensors work for this credit. Make sure the shut off is timed to 30 minutes or less. Occasional use between 11pm-5am (cleaning crew) is fine as long as the override is 30 minutes or less.

If you are planning to use a space for a large portion of time between 11pm-5am the it would be good to allow only 50% of the lights on between these hours.

Post a Reply
0
0
Suzanne Allerton Architect W2A Design Group
Feb 27 2012
LEEDuser Member
521 Thumbs Up

All exterior mounted fixtures

Do facade mounted fixtures need to be shown on the photometric plan?
We received this comment in the first review
"Provide a revised photometric site plan with all exterior mounted fixtures included. Ensure that the quantity of luminaries are consistent between all credits."

1
8
0
Bill Swanson PE, LEED AP, Integrated Architecture Feb 27 2012 LEEDuser Expert 10086 Thumbs Up

Yes, and included in the uplight calculation.

2
8
0
Suzanne Allerton Architect, W2A Design Group Feb 27 2012 LEEDuser Member 521 Thumbs Up

Thank you for the quick response. Would a
site sign with back lit letters also need to be shown
on the photometric? The sign is within a masonry base.

3
8
0
Bill Swanson PE, LEED AP, Integrated Architecture Feb 27 2012 LEEDuser Expert 10086 Thumbs Up

Typically, internally lit signage is ignored.

4
8
0
Suzanne Allerton Architect, W2A Design Group Feb 27 2012 LEEDuser Member 521 Thumbs Up

thank you again.
Would back lit facade lettering be ignored also?

5
8
0
Bill Swanson PE, LEED AP, Integrated Architecture Feb 27 2012 LEEDuser Expert 10086 Thumbs Up

Does light exit the sign anywhere except thru the letters? If not, I would consider it interally lit and ignore it.

6
8
0
Suzanne Allerton Architect, W2A Design Group Feb 27 2012 LEEDuser Member 521 Thumbs Up

thanks again Bill - last question on this subject...
what about lights under canopies... on the photometric or
ignore them?

7
8
0
Bill Swanson PE, LEED AP, Integrated Architecture Feb 27 2012 LEEDuser Expert 10086 Thumbs Up

If outside of the building envelope include on the photometric plan and in the uplight calculation.

8
8
0
Todd Reed Daylight Designer, 7group Feb 27 2012 LEEDuser Expert 3584 Thumbs Up

The only way that you could exempt any exterior fixture is to show that it is wired on a separate emergency circuit. Otherwise, any all must be included in your site 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. calculations and your photometric site analysis.

Post a Reply
0
0
Suzanne Allerton Architect W2A Design Group
Jan 18 2012
LEEDuser Member
521 Thumbs Up

LEED for Schools 2007

Our school is pursuing this credit under a final review.
All interior lighting is off between the hours of 11pm and 6am.
Therefore: Shall we indicate this as an Alternative Compliance Path.

1
4
0
Bill Swanson PE, LEED AP, Integrated Architecture Jan 18 2012 LEEDuser Expert 10086 Thumbs Up

Why do you think this is an Alternative Compliance Path? This sounds like you are complying with Option 1 for interior lighting. How do you know the lights will be off at night? Are they on occupancy sensors or is this some sort of promise to turn off the lights before leaving for the night?

2
4
0
Suzanne Allerton Architect, W2A Design Group Jan 18 2012 LEEDuser Member 521 Thumbs Up

Thanks I reread the option 1... didn't see less than wording

3
4
0
Andrew McIntyre Aug 03 2012 Guest 20 Thumbs Up

Bill-
What if a owner promises(states) to have all exterior lights off at night(11pm - 5am)

4
4
0
Bill Swanson PE, LEED AP, Integrated Architecture Aug 03 2012 LEEDuser Expert 10086 Thumbs Up

The Credit language says "automatic control".

Staff get shifted around, Owners change, hours of work change. The realities of a dynamic business world makes many of these promises impossible to follow after the first couple of years.

Post a Reply
0
0
Suzanne Allerton Architect W2A Design Group
Nov 08 2011
LEEDuser Member
521 Thumbs Up

LPD per fixure and zone lumen chart locations

I am having difficulty finding these items. Our lighting rep is also
having this difficulty. Our particular fixtures are not on the
website previously mentioned. any suggestions?

1
5
0
Bill Swanson PE, LEED AP, Integrated Architecture Nov 08 2011 LEEDuser Expert 10086 Thumbs Up

I'm not understanding your question well. Are you refering to my post on Aug 18 2011?

"LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space. per fixture" does not make sense.

The website I mentioned on Aug 18 2011 can use any IES file to show you the % of uplight and the BUG rating.

"If you want the information for the IES file on your hard drive then click the "My Files" tab at the top."

2
5
0
Suzanne Allerton Architect, W2A Design Group Nov 08 2011 LEEDuser Member 521 Thumbs Up

Bill, The IES file for any brand name will be listed?
Not just those indicated?

Also relative to canopy vs Main entry door lighting.LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space.
We meet the criteria for canopy at the Main door.

There is no other lighting at the Main entry. Is this
compliant then?

3
5
0
Bill Swanson PE, LEED AP, Integrated Architecture Nov 08 2011 LEEDuser Expert 10086 Thumbs Up

No. The website only has the IES files from Acuity Brand companies. But they allow you to upload any IES file that you have.

Click this link,
http://www.visual-3d.com/tools/photometricViewer/default.aspx

Click "Open" at the top left of the screen.

Now, at the top center of the screen are 3 tabs. The first one is "Catalog" and is blue. That just shows the companies they have IES files for. The second tab "My Files" is black. Click that one.

Now click the "Browse" button. Find the IES file you want information about on your hard drive or network drive. Then "Select". Now you should see all of the tables and graphs.

Still not sure what you mean regarding LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space.. I can't tell you if the main entry is compliant or not. Canopies and doors are part of the tradable surfaces. The site is either compliant or not. The entry is just one piece of the site.

4
5
0
Suzanne Allerton Architect, W2A Design Group Nov 08 2011 LEEDuser Member 521 Thumbs Up

Thank you - this is very helpful. Can you explain
tradable surfaces again? If we are a little over in one
area but the total site is fine are we on track to get the
point?

5
5
0
Bill Swanson PE, LEED AP, Integrated Architecture Nov 08 2011 LEEDuser Expert 10086 Thumbs Up

Just like using the space-by-space method for interior lighting. You can be low in some areas and high in other areas as long as everything combined is low.

Post a Reply
0
0
Kimberly Cullinane
Nov 03 2011
LEEDuser Member
321 Thumbs Up

Campus Projects

Two questions here: (1) The 2010 AGMBC, which is USGBC's guidance for campus projects, shows in table 1A at the end the credits that may be pursued as campus credits - Site Credit 8 does not appear here. I am assuming this is an oversight? And, (2) in the PreDesign checklist above, there is a statement that "Project teams are only responsible for lights that are part of their project. For example, municipal lights about which the project has no control do not need to be considered." I do not see this in the Reference Guide anywhere - can you point to where you find this? Thank you!

Post a Reply
0
0
Suzanne Allerton Architect W2A Design Group
Nov 03 2011
LEEDuser Member
521 Thumbs Up

Exterior Facade - Lighted Letters - signage

Can you clarify the requirements for lighted letters on the
building facade? Thank you for all info available.

1
1
0
Bill Swanson PE, LEED AP, Integrated Architecture Nov 03 2011 LEEDuser Expert 10086 Thumbs Up

The power these use would be excluded from your 90.1 compliance calculation because they are advertising.

You still need to count it for light pollution. It probably won't have an affect on perimeter light levels but it does affect uplight. I assume 50% of the signage light is uplight. Count that in your calculation for total site uplight.

Post a Reply
0
0
Jean Marais b.i.g. Bechtold DesignBuilder Expert
Aug 18 2011
LEEDuser Member
5362 Thumbs Up

Exterior Lighting - Cutsheets to Lumens above Nadir

I don't see how one goes from the candela - degrees diagram and translate that into how many lumens are above nadir...what's the limit on % anyway?

1
1
0
Bill Swanson PE, LEED AP, Integrated Architecture Aug 18 2011 LEEDuser Expert 10086 Thumbs Up

Let's look at an example.
http://www.visual-3d.com/tools/photometricViewer/default.aspx?id=27333

The first table on this page is down a little bit and called "Zonal 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. Summary"
In the 90-180 Zone they show 3.2 lumens. This is less than 0.1% of the total output of 6,173.7 lumens for the whole fixture. Almost nothing but it still prevents this fixture from being used in LZ0 or LZ1 because it's more than 0% uplight.

Now let's assume there's also a typical wall pack on the building exterior.
http://www.visual-3d.com/tools/photometricViewer/default.aspx?id=13334

This fixture has 523 lumens in the 90-180 Zone. Out of 2,662 lumen total output.

If you had a project with (5) area lights from the first link I sent you and (2) wall packs from the second link I sent you, the total uplight would be, (5 * 3.2) + (2 * 523) = 1,062 lum.
Total site light is (5 * 6,173.7) + (2 * 2,662) = 36,192.5 lum.
% Uplight for site is: 1,062 / 36,192.5 = 2.9%

This sample site would only comply with LZ3 or LZ4 locations. If your project is located in LZ2 then you'd either have to remove a wall pack or change the style of wall pack to something with less uplight.

If you can't find a table like this for your light fixture all you need is the IES file.

Go to this page.
http://www.visual-3d.com/tools/photometricViewer/default.aspx

Click "Open". Then the brand names they have available files for will be listed. If you want the information for the IES file on your hard drive then click the "My Files" tab at the top.

Post a Reply
0
0
Lisa Logan LEED AP BD+C Green Ideas
May 09 2011
Guest
480 Thumbs Up

Existing lighting in project boundary

My project boundary includes a baseball playing field which will be new - but the lighting around it is existing. Our reviewer wants info on that lighting but to find IES photometric files for existing luminaires is often close to impossible if they’re 5+ years old poles. Can we exclude the lighting?

1
5
0
Bill Swanson PE, LEED AP, Integrated Architecture May 09 2011 LEEDuser Expert 10086 Thumbs Up

If the Owner has the shop drawings you may find a sheet showing light levels outside of the field.

There is nothing officially shown anywhere that excludes sports lighting for this Credit. Even with shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. these fixtures will have a sizeable amount of spill light and uplight.

I've suggested to others with advertising and directional markers to argue they are excluded because ASHRAE 90.1 and the Pilot Credit exclude them. You can try this approach with the athletic playing area lighting. Say you are trying to be consistent in applying this credit.

If they reject that arguement then you can always try the Pilot Credit which does specifically exempt this lighting.

2
5
0
Bill Swanson PE, LEED AP, Integrated Architecture May 09 2011 LEEDuser Expert 10086 Thumbs Up

This is also interesting because I've never heard of a reviewer asking for existing fixtures to be compliant before.

3
5
0
Todd Reed Daylight Designer, 7group May 19 2011 LEEDuser Expert 3584 Thumbs Up

If its within the LEED boundary and included in your EAc 1 calcs, then you need to include for SSc 8. If it is not under LEED for Schools, i recommend that you document the credit following the LEED for Schools requirements for Sports Lighting.

4
5
0
Lisa Logan LEED AP BD+C, Green Ideas Jul 20 2011 Guest 480 Thumbs Up

Bill - comments are back and the credit was denied. My question is - in the LEED for Schools 2007 (which is what this project is registered under) it says "note that physical education spaces (playing fields) do not need to comply with the lighting power density requirements of this credit, as per ASHRAE 90.1 section 9.4.5, exception E." What am I missing here? The lights exist to light the baseball field - the field is included in the boundary because the field is being replaced - lighting remains. Your thoughts? I am assuming I will need to appeal but this just doesn't seem right.

5
5
0
Bill Swanson PE, LEED AP, Integrated Architecture Jul 25 2011 LEEDuser Expert 10086 Thumbs Up

ASHRAE 90.1 is different than the lighting trespass levels. It sounds like the reviewer is following this by the letter of the Credit. So the sports field doesn't have to comply with the W/sf but they are still demanding that light levels around the project boundary and uplight % comply with this Credit. I don't see how sports lighting can comply with either of these requirements.

You can try appealing and argue these are existing fixtures. And the very nature of sports lighting makes this compliance impossible which is why the Pilot Credit excludes this type of lighting. I personally hate spending the customer's money in an appeal but if this credit is needed then you may have to. At least a different reviewer will be looking at it and they may be more sympathetic to you.

If you have any unused ID credits try going for the Pilot Credit.

Post a Reply
0
0
Tim Hoeft Associate AIA, LEED AP Straughn Trout Architects, LLC
Nov 23 2010
LEEDuser Member
419 Thumbs Up

Campus Walkway Lighting - Light Tresspass beyond LEED Boundary

Under Checklists:Pre-design on this site, it states:
"Campus projects can choose whether to comply with the requirements for the building site boundary or to meet the light trespass requirements for the campus as a whole."

Can someone help clarify the basis of this statement and where it refers to that in the LEED Reference Manual? It makes sense that if your project has exterior light tresspass beyond the LEED project boundary it would be acceptable as long as it remains within the campus boundary, especially in areas of lighted walkways between buildings. Can anyone provide some advice on successful narratives that have addressed this issue and been granted an exception by the GBCI reviews? Much thanks!!

1
5
0
Andy Malanowski Boer Architects Nov 23 2010 Guest 29 Thumbs Up

I am interested in this too. The new AGMBC came out in October and under the old one you could do that, but from my understanding of the new one, you can't anymore. Our preliminary design reviewers came back (before the new guide was published) and said light traspass beyond the project boundary but within the campus boundary was unacceptable because we didn't do photometrics for the entire campus. (which is impossible)
It seems replacing all fixtures on a campus because you are doing one LEED project would be prohibitively expensive. Especially since the light that does trespass is providing a necessary level of light for life safety.

2
5
0
Bill Swanson PE, LEED AP, Integrated Architecture Nov 23 2010 LEEDuser Expert 10086 Thumbs Up

You need to either show the project meets the LEED boundary requirements or that the campus meets the LEED boundary requirements. Most universities are not going to have IES files for 20-50 year old lights to be able to do the calculation with.

I've seen Harvard earn this point by providing a copy of their design standards for the campus and they promised that all lights will comply with LEED requirements for the campus as a whole. No promises that this same tactic would work now.

3
5
0
Kimberly Cullinane Jan 29 2011 LEEDuser Member 321 Thumbs Up

I'm wondering if anyone has any further guidance on these matters since this topic was posted. I'm working on a project on a campus, but it is the only anticipated LEED project on the campus. I read through the 2010 AGMBC and it seemed that it only really applies if you have multiple projects pursuing LEED on the same campus. In our case, we have just one project, and I am assuming that we can structure our LEED project boundary in a reasonable way that makes sense to us without using the campus approach. However, if we do that, we will have trouble with the Site Lighting credit because we will definitely have light spilling onto other parts of the campus, which really should not be a problem as a practical matter.

4
5
0
Bill Swanson PE, LEED AP, Integrated Architecture Jan 31 2011 LEEDuser Expert 10086 Thumbs Up

I have not heard anything new but would love to hear from others.

5
5
0
Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Jan 31 2011 LEEDuser Moderator

What Bill said above remains true. Campus projects can choose whether to comply with the requirements for the building site boundary or to meet the light trespass requirements for the campus as a whole. The latter case is going to be common for projects taking the AGMBC approach. Either approach can be very difficult, as you indicate.

Post a Reply
0
0
Joanna Yaghooti Director of Sustainable Design PageSoutherlandPage
Jul 14 2010
LEEDuser Member
328 Thumbs Up

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?)

1
1
0
Bill Swanson PE, LEED AP, Integrated Architecture Jul 14 2010 LEEDuser Expert 10086 Thumbs Up

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.

Post a Reply
0
0
Scott Ennis
May 26 2010
LEEDuser Member
48 Thumbs Up

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?

1
2
0
Bill Swanson PE, LEED AP, Integrated Architecture May 26 2010 LEEDuser Expert 10086 Thumbs Up

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.

2
2
0
Bill Swanson PE, LEED AP, Integrated Architecture May 26 2010 LEEDuser Expert 10086 Thumbs Up

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.

Post a Reply

Start a new LEED comment thread

Welcome !
Jun 20 2013
Type the characters you see in this picture. (verify using audio)
Type the characters you see in the picture above; if you can't read them, submit the form and a new image will be generated. Not case sensitive.

Copyright 2013 – BuildingGreen, Inc.