Jim Brodrick on LED Lumen Maintenance and Light Loss Factors

Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program

by Jim Brodrick, U.S. Department of Energy

All lighting systems decline in lumen output over time, due to reductions in lamp emissions and changing surface properties. This decline is typically accounted for by applying a light loss factor (LLF) during the design process. An LLF is a multiplier that’s used to predict maintained illuminance based on the initial properties of a lighting system.

A new article published in Leukos: The Journal of the Illuminating Engineering Society of North America (IES) discusses complications related to the lamp lumen depreciation (LLD) light loss factor and LEDs. Entitled “Lumen Maintenance and Light Loss Factors: Consequences of Current Design Practices for LEDs,” the article compares the performance of some conventional and LED products, and examines alternatives to the currently recommended approach for determining LLD factors for LED products. It was written by Michael Royer of Pacific Northwest National Laboratory, a member of the U.S. Department of Energy (DOE) solid-state lighting team.

Light loss factors are used to help lighting systems meet quantitative design criteria throughout the life of the installation, but they also have other consequences, such as influencing first cost and energy use. Because of the unique operating characteristics of LEDs and lack of a comprehensive lifetime rating — as well as the problematic relationship between SSL lifetime and lumen maintenance — determining an appropriate LLD factor for LED products is difficult.

For LED-based lighting systems, the IES recommends using an LLD of no greater than 0.70 when the quantity of the light is an important design consideration. This approach deviates from the practice of using the ratio of mean to initial lumen output — which is typically used with conventional sources — and may misrepresent actual performance, increase energy use, and inhibit comparisons between products.

With all of the effort that’s put into improving luminous efficacy in the name of energy efficiency, the effect of LLFs on energy use may deserve more attention, with more care given to using an LLD that best represents expected performance for a given installation. For example, a change in LLD from 0.70 (resulting in an initial light level at 143 percent of the target) to 0.80 (initial light level at 125 percent of the target) can reduce energy consumption by roughly 13 percent over the life of the system.

For LED lamps and luminaires, the rated lifetime provided by manufacturers is typically based on only the lumen maintenance of the LED package, which has become the de-facto method for providing rated lifetime for LED products. Although the lumen maintenance lifetime of LED architectural lighting products is almost always based on L70 (the time it takes for the lumen output to fall to 70 percent of what it was originally), this is not helpful for calculating an LLD factor. As an alternative, it may be more appropriate to instead use a known end point (e.g., the building being renovated in 15 years) in establishing the end of life used for lighting calculations. This would allow specifiers to more easily distinguish between products with different lumen depreciation characteristics and design systems that are more energy-efficient over their lifetime.

Instead of giving lumen maintenance in terms of L70, it may be more useful for manufacturers to report the lumen maintenance at a given number of hours of use — such as at 25,000 hours, which is already being adopted by the LED Lighting Facts® program. This would allow for expedient product comparisons using manufacturer literature.

Although it may seem a prudent approach for a relatively unproven technology such as SSL, there are considerable consequences to capping the LLD for LEDs at 0.70. Effectively applying the same LLD to all LED products ignores the large variation in performance and is inconsistent with current methodology for characterizing other lighting systems. Long-term test data show that 0.70 is far too conservative for some LED products and hinders efforts to ensure specification of high-quality products. But the current link between LED rated lifetime and lumen maintenance effectively precludes the use of traditional methods for calculating LLDs.

Any revised method for determining LLDs should be consistent across different light-source technologies and allow for effective comparisons of product performance, so that specifiers can differentiate products with less depreciation over time. In turn, this can save substantial amounts of energy and provide a more pleasing visual environment.

For a much more in-depth treatment of this important topic, please see the full article, which is accessible from the DOE SSL website.

IESNY Announces Winners of 2014 New York City Student Lighting Competition

studentOut of an unprecedented 160 student submissions from the New York City-area, “Livre Noir,” designed by Esli Teker, attending Parsons The New School of Design, won First Prize in the Illuminating Engineering Society New York City Section’s (IESNYC) 14th annual Student Lighting Competition. Teker’s project, “Livre Noir,” can be described as a book that’s full of secrets and these confidences can only be read once the book is touched and it becomes illuminated. The installation engages several of the senses and beckons interaction. By touching the “black book,” it produces different colors and elicits various moods. As viewer flip through the pages of the book, they are invited to share their own feelings. Teker will receive a cash award of $2,000 from the section.

Second prize was awarded to Pratt Institute’s Ia-Chi Pan and third prize went to Jordan Ringdahl also of Pratt, who will receive $1,000 and $500 respectively.

Additionally, four students and their projects received honorable mentions.

The Student Lighting Competition, which is one of the IESNYC’s signature events, demonstrates the section’s support for students and lighting programs. This year’s event was held in honor of Patricia DiMaggio (1964-2014), LC, a lighting project design manager at Osram Sylvania and a lighting educator at New York School of Interior Design (NYSID). DiMaggio started the Student Lighting Competition during her tenure as president of the IESNYC (2004-2005). The section is establishing a fund that will continue to give financial assistance to lighting students, a cause championed by DiMaggio.

As in previous years, students were tasked to apply their education, ingenuity, and skills in order to take an elusive concept and transform it into a three-dimensional illuminated visual experience. “This year’s theme asked students if they could ‘touch with their eyes’ and challenged them to consider how light conveys the sensation of touch,” says Erin Gussert, LEED AP, lighting designer at Kugler Ning Lighting Design and co-chair of the IESNYC Student Lighting Design Competition.

Check out the winners here:

IES 2014 Student Competition Winners from Colin Weber on Vimeo.

Product Monday: Light-Emitting Acoustic Ceiling by Philips and Ecophon

Lighting manufacturer Philips and Saint-Gobain Ecophon, a global supplier of acoustic systems, recently launched a new version of their jointly developed light-emitting acoustic ceiling. The new SoundLight Comfort Ceiling Tunable White enables dynamic lighting, designed to support the human body’s natural biorhythm to aid wellbeing and productivity. It is based upon the known benefits of SoundLight Comfort Ceiling launched in 2012.

SoundLight Comfort Ceiling Tunable White incorporates programmable lighting controls that change the brightness and warmth of office lighting throughout the working day. This supports employees’ energy levels, which can be diminished by spending too much time indoors. SoundLight Comfort Ceiling Tunable White helps to reverse this by simulating “daylight inside” and helping to maintain the body’s natural connection to the sun.

The light-emitting ceiling also enables a more stimulating, inspiring and attractive open plan office environment by limiting ceiling clutter and creating the impression of a bigger space, while its acoustic nature minimizes noise disturbance. It is designed to be easy to install in either new or existing offices.

Click here to learn more.

Here’s a video describing the SoundLight Comfort Ceiling:

Precision-Paragon Publishes Retrofit Guide

P2Lighting manufacturer Precision-Paragon [P2] has published a guide to help building owners and lighting professionals identify and maximize potential sources of energy savings. The 21-page publication, “6 Steps to Getting the Most From Every Lighting Retrofit,” is available for free as a downloadable e-book on the lighting manufacturer’s website here.

The guide’s first chapter opens at the starting point for nearly all lighting upgrades: a one-for-one replacement, where existing fixtures are swapped out with more energy-efficient replacements. The book covers additional steps, including performing a comprehensive layout and specification, adding automatic lighting controls, addressing outdoor lighting, addressing specialty lighting, and finding and qualifying for rebates and incentives. These steps can ensure that energy savings and other benefits are maximized.

IALD Will Bring Enlighten Europe to Berlin in November 2014


The International Association of Lighting Designers (IALD) has announced the IALD Enlighten Europe conference for November 9-11, 2014 at the andel’s Hotel Berlin in Berlin, Germany.

Enlighten Europe will provide an inspiring and cutting-edge educational program in three subject-matter tracks, while offering exciting networking opportunities in the vibrant city of Berlin.

Click here to learn more.

Career Opportunity: Research and Evaluation Analyst (Conservation Programs) for Seattle City Light


SALARY: $34.32 – $39.96 Hourly
LOCATION: 901 – 5th Ave, 19th floor, Seattle,, Washington
JOB TYPE: Classified Civil Service, Regular, Full-Time
DEPARTMENT: Seattle City Light
BARGAINING UNIT: PTE, Local 17 – Professionals
CLOSING DATE: 04/28/14 04:00 PM Pacific Time


Seattle City Light, a department of the City of Seattle, is one of the nation’s largest municipally owned utilities. Over the years we have worked very hard to keep Seattle’s electricity affordable, reliable, and environmentally sound. Today, City Light is a recognized national leader in energy efficiency and environmental stewardship. The Conservation Resources Division of Seattle City Light provides energy conservation programs which are the most cost-effective, and environmentally-friendly mechanism to meet the energy needs of our customers

The Conservation Resources Division is looking for two (2) Energy Research and Evaluations Analysts who will complete a three person evaluation team in the Planning, Implementation and Evaluation group. Research enables City Light to stay on top of emerging technology opportunities and evaluation entails rigorous review, monitoring, and verification of energy program impacts and other information. These positions work under the general supervision of an Energy Planning Supervision.


The Energy Research and Evaluation Analysts plan, develop and conduct evaluations, and research, analyze, interpret, and presents statistical reports and evaluations in support of the energy conservation division’s programs and activities.

• Experience in study design and methodologies, evaluation procedure, statistical techniques, analysis and inference, database designs.
• Knowledge of statistical and economic analysis as well as research methodologies.
• Awareness and understanding of current and emerging techniques in energy program evaluation.
• Serves as project manager and conducts evaluation of energy efficiency and conservation programs. Plans and conducts analyses, and interprets, prepares and presents statistical reports substantiating evaluations in support of department programs and activities.
• Manage large consultant contracts. Define scope of work, coordinate RFP processes, participate in selection and manage the work of independent contractors.
• Significant computers skills. Ability to establish and maintain databases as well as using word processing, spreadsheet, and statistical software.
• Provides recommendations to modify and/or continue programs and regulations.
• Present finding in orally and in writing.
• Participates in planning committees and provides technical assistance as required.
• Interact with City, City Light and Conservation Resources Division Leadership and staff to assist with the development of new and innovative programs and delivery mechanisms and identify appropriate evaluation methods. Represent the Conservation Resources Division.
• Performs other related duties of a comparable level/type as assigned.


Education: Bachelor’s Degree in social or behavioral science or in a related field involving research design and statistical analysis

Experience: Three years related work experience.

(or a combination of education and/or training and/or experience that provides an equivalent background required to perform the work of the class).

Certification/License: Washington State Driver’s License or equivalent mobility.


Desired Qualifications:

• Graduate degree in Statistical Analysis, Business Administration, Public Administration or thou field that provides experience in research and evaluation methods.
• Substantial professional experience in research or evaluation of energy efficiency or conservation programs, services or related areas. This experience is typically gained through five or more years of experience performing relevant progressively responsible assignments.
• Experience in study designs and methodologies, evaluation procedures, statistical techniques, analysis and inference, database designs, and recommendations to modify and /or continue programs and regulations.
• Awareness and understanding of current and emerging techniques in energy conservation and energy program evaluation.
• Significant computer skills. Ability to establish and maintain databases as well as using office products and statistical software.
• Ability to deliver oral presentation.
• Experience producing statistical and research reports, manuals, customer and program data analysis and annual reporting.
Job offers are contingent on the verification of credentials and other information required by the employment process including the completion of a background check which includes criminal history and driving history review.

Want to know more about Seattle City Light? Check out our web page: http://www.seattle.gov/light/.

Hubbell’s Chris Bailey on Right-Sizing Light

Chris Bailey, Director of Lighting Solutions Center – Hubbell Lighting, recently published a post on the Hubbell blog, “Right-sizing Light,” that you might find interesting. He writes:

“Most designers strive to achieve a balance in the perceptions of safety, security and nighttime enjoyment. While it is essential for designers and customers to understand the technical requirements of outdoor lighting, the implications of failing to yield to the more elusive requirements of the environment can be equally significant. However, we should hold one governing tenant in mind at all times; applying light outdoors should be driven from a real need and with great care to avoid both unintentional human an environmental consequences.”

Click here to read the rest of this post.

Architecture Billings Index Shows Slight Improvement

After starting out the year on a positive note, there was another minor increase in the Architecture Billings Index (ABI) last month. As a leading economic indicator of construction activity, the ABI reflects the approximate nine to twelve month lead time between architecture billings and construction spending.

The American Institute of Architects (AIA) reported the February ABI score was 50.7, up slightly from a mark of 50.4 in January. This score reflects an increase in design services (any score above 50 indicates an increase in billings). The new projects inquiry index was 56.8, down from the reading of 58.5 the previous month.

(Click here for an interesting report on how the construction industry can use the ABI to its advantage.)

“The unusually severe weather conditions in many parts of the country have obviously held back both design and construction activity,” said AIA Chief Economist Kermit Baker, Hon. AIA, PhD. “The March and April readings will likely be a better indication of the underlying health of the design and construction markets. We are hearing reports of projects that had been previously shelved for extended periods of time coming back online as the economy improves.”

Key February ABI highlights:

• Regional averages: South (52.8),West (50.5), Northeast (48.3), Midwest (47.6)

• Sector index breakdown: multi-family residential (52.5), commercial / industrial (51.9), institutional (49.6), mixed practice (46.6)

• Project inquiries index: 56.8

Note the regional and sector categories are calculated as a 3-month moving average, whereas the national index and inquiries are monthly numbers.


Product Monday: MegaLum Cylinder by Prescolite

ICYMI - Prescolite Elevates LED Downlighting to New Heights-2Prescolite has introduced a 12,000+ lumen LED luminaire designed for high-ceiling commercial and architectural interiors where recessed depth is not available—the MegaLum Cylinder. With all the performance advantages of the company’s MegaLum luminaire, the MegaLum Cylinder can be surface, cable or pendant mounted and offers a viable alternative to T4 quartz (up to 500W) and metal halide (up to 250W) sources for ceiling heights of 20 to 60 feet.

Delivering over 12,000 lumens out of a 10” cylinder with 168W of input power, the MegaLum Cylinder uniformly illuminates large, open spaces including convention centers, airports, auditoriums, churches and performing arts centers. It’s available in four lumen packages (3,000, 6,000, 9,000 and 12,000) and five color temperatures (2700K, 3000K, 3500K, 4000K and 5000K), utilizing up to 480 individual LEDs specifically mixed to provide a minimum of 80 CRI with 3 SCDM color consistency. The reflectors create precise optical control in 25-, 35-, 45- and 55-degree distributions.

Rated life of 50,000 hours. The entire external housing can be simply lowered by loosening two side screws and sliding the tube down to a safety stop, making the drivers and wiring easily accessible. Housings available in brushed aluminum, matte black, matte white, zet, and bronze. The fixture can be configured to be Hubbell Building Automation wiHUBB compatible. It comes standard with 0-10V dimming to 10%, with multiple 1% dimming options.

Click here to learn more.

Lighting Rebate Trends for 2014

briteswitchRebate organizations have been busy updating their rebate and incentive programs for 2014. While not all of them operate on a calendar year, BriteSwitch, LLC still sees a lot of changes and trends in the industry. Right now, 71% of the country is covered by an active commercial lighting rebate. BriteSwitch has also noticed a few other trends:

Programs are getting new funding. Last year, quite a few rebate programs, such as Consumers Energy in Michigan and SureBet Nevada, exceeded their budget, ending the programs earlier than planned. This year, they have new funding again and are accepting applications for 2014 projects. Click here to see a map with how lighting rebates have changed in the past 5 years.

More prescriptive programs for LED products. More organizations are now offering prescriptive rebates for a larger variety of LED solutions such as LED high-bay fixtures, LED outdoor pole lights, TL fixture replacements, and even some LED T8 replacements. In 2014, LED rebates have continued to expand with 16% more prescriptive rebates than last year. The dollar amounts have remained relatively stable compared to last year, which is surprising given the falling prices of LEDs. Click here to see the average rebate amounts for LEDs.

T12 rebates continue to decline. As expected, T12 to T8 rebates took a tumble this year compared to 2013. Because it is becoming harder to find replacement T12 lamps and ballasts, many rebate programs feel they don’t need to offer incentives anymore for people to upgrade. Between this year and last year, the number of rebates available for T8 installations decreased by 18%. While the dollar amount of the rebate remains relatively stable from last year, many programs are requiring the use of high performance or reduced wattage T8 lamps. In fact, 60% of T8 rebates require lamps and ballasts that satisfy CEE specifications. Click here to learn more about T12 to T8 rebates.