According to independent product testing by the Department of Energy (DOE), LED is proving to offer viable alternatives to conventional lighting in many popular applications. As a young technology, LED lighting has certainly come a long way in a short time, but it does carry risks, just as any new technology would have.These risks can be mitigated by being an educated consumer — not just about LED, but about lighting in general — to ensure that these new products fit properly into their intended applications.
LED lighting offers many benefits: high efficiency, long life, compact size, no mercury, no filaments or arc tubes to break, and no heat or ultraviolet energy in its transmission. The designer should understand principles of good lighting and consider the complete story of a lighting product, including attributes such as color quality, luminaire spacing, form factor, light pattern, compatibility between devices and controllability. The designer should also understand the application so as to put all of these attributes into context for a good fit. Deep understanding will reveal the right choice of technology and product. The more demanding the lighting application, the greater the need for a high-quality product in this get-what-you-pay-for era in LED lighting.
The designer should get to know the technology through education and experimentation with samples. Even though LED luminaires may appear in familiar forms such as recessed downlights, they behave differently than conventional sources. One of the most important differences is lumen depreciation. LEDs exhibit a higher level of lumen depreciation than many conventional light sources, with ambient heat being a major consideration, since heat buildup in the LEDs degrades light output. A well-designed product with good thermal management (known as heat sinking) will maintain higher light output over time. Dimming also results in cooler operation and can support lumen maintenance. Some products feature on-board lumen management capability, using dimming to maintain constant light output over the life of the product.
Modules that incorporate the LED engine, heat sink and driver in a single unit enable replacement without having to change the entire LED luminaire. Satco Products’ Kolourone module shown.
Lumen depreciation is typically indicative of the failure mode, with products rated at L70, L80, etc. This indicates rated life in hours at a point where light output has degraded to 70 or 80 percent of the original rating and so on. In applications where maintaining target light levels is critical, the product should have some type of end-of-life indicator or the owner must otherwise take responsibility for replacing the product when it is no longer properly serving the application. The driver may also fail, providing a clear end-of-life signal.
What will actually be replaced is determined during specification. LED luminaires are typically integrated devices consisting of the LED light engine, heat sink, driver electronics and luminaire. This means at end of life, the entirety of a fixture will need to be replaced. A growing number of products offer modular designs isolating the LED engine, heat sink and driver as separate components that can be serviced or upgraded. This provides a durable luminaire while enabling it to be upgraded as source technology continues its rapid development. Some products are based on a proprietary platform, with the owner tied to a single manufacturer, while some are based on Zhaga specifications, which offer the luminaire as an open platform with interchangeability among vendors.
Another example of how LED is different than conventional lighting is in color quality. Color rendering ability of conventional light sources is expressed using the color rendering index (CRI). The shortcomings of this popular metric have been accepted for decades but are more pronounced with LED lighting, which has a spectral emission distinct from conventional sources. As a result, some red-blue-green LED combinations suffer low CRI ratings even though they may visually appear right. Conversely, CRI may be high while the source is visually poor to the eye. Alternative metrics such as the Color Quality Scale have been proposed but are not yet widely accepted. At this time, there is no substitute for sampling a product to see firsthand how it renders skin tones and other critical colors.
The above discussion raises a final point. When evaluating LED products, it is useful to become familiar with new industry metrics designed to address the unique characteristics of the technology. IES-LM-79-2008, for example, details a testing standard for total light output, luminaire efficacy, chromaticity, color temperature and other characteristics. IES-LM-80-2008 lays out a method to test lumen depreciation for LED packages, modules and arrays from 6,000 to 10,000 hours, while IES-TM-21-2011 provides a procedure for extrapolating this data to estimate light output to end of life.
It’s an exciting time for the lighting industry as LED and other SSL technologies continue to fight their way to the forefront of many specifications. These technologies offer many benefits, but designers should be cautious about selecting product. Fortunately, many resources are now available to enable educated decisions.
LED RESOURCES
Government and industry have invested considerable resources to protect consumers during this time of market transformation. These resources provide designers with valuable tools they can use to identify and evaluate quality LED products.
DOE SSL Program: The DOE SSL program includes a variety of market transformation activities and free reports, including independent product testing, product demonstrations, market analysis and other useful information and tools. Learn more at
www.ssl.energy.gov.
Lighting Facts Label: Lighting Facts is a voluntary labeling program that provides a quick snapshot of lighting performance in a consistent format based on standardized testing. Thousands of products use it.
Learn more at www.lightingfacts.com.
ENERGY STAR: ENERGY STAR is another voluntary label that indicates that a given product performs as well as the conventional lighting product it is intended to replace, while saving energy. Covered products include some categories of commercial and residential luminaires, as well as retrofit lamps. Learn more at www.energystar.gov.
Qualified Products List: The Qualified Products List, maintained by the DesignLights Consortium, goes beyond ENERGY STAR to include 19 product categories and numerous performance aspects. Some utilities rely on the Qualified Products List to identify products suitable for rebates. Learn more at www.designlights.org.
Next Generation Luminaires Design Competition (NGLDC): The NGLDC is a commercial luminaire design competition that recognizes many of the best LED fixtures in the market based on rigorous criteria. Learn more at www.ngldc.org.
Lighting for Tomorrow: Lighting for Tomorrow is an awards program similar to the NGLDC, but it honors products geared to the residential market. Learn more at www.lightingfortomorrow.com.
Related Stories
| Aug 11, 2010
Florida mixed-use complex includes retail, residential
The $325 million Atlantic Plaza II lifestyle center will be built on 8.5 acres in Delray Beach, Fla. Designed by Vander Ploeg & Associates, Boca Raton, the complex will include six buildings ranging from three to five stories and have 182,000 sf of restaurant and retail space. An additional 106,000 sf of Class A office space and a residential component including 197 apartments, townhouses, ...
| Aug 11, 2010
Restoration gives new life to New Formalism icon
The $30 million upgrade, restoration, and expansion of the Mark Taper Forum in Los Angeles was completed by the team of Rios Clementi Hale Studios (architect), Harley Ellis Devereaux (executive architect/MEP), KPFF (structural engineer), and Taisei Construction (GC). Work on the Welton Becket-designed 1967 complex included an overhaul of the auditorium, lighting, and acoustics.
| Aug 11, 2010
Best AEC Firms to Work For
2006 FreemanWhite Hnedak Bobo Group McCarthy Building Companies, Inc. Shawmut Design and Construction Walter P Moore 2007 Anshen+Allen Arup Bovis Lend Lease Cannon Design Jones Lang LaSalle Perkins+Will SmithGroup SSOE, Inc. Timothy Haahs & Associates, Inc. 2008 Gilbane Building Co. HDR KJWW Engineering Consultants Lord, Aeck & Sargent Mark G.
| Aug 11, 2010
High-Performance Workplaces
Building Teams around the world are finding that the workplace is changing radically, leading owners and tenants to reinvent corporate office buildings to compete more effectively on a global scale. The good news is that this means more renovation and reconstruction work at a time when new construction has stalled to a dribble.
| Aug 11, 2010
Great Solutions: Business Management
22. Commercial Properties Repositioned for University USE Tocci Building Companies is finding success in repositioning commercial properties for university use, and it expects the trend to continue. The firm's Capital Cove project in Providence, R.I., for instance, was originally designed by Elkus Manfredi (with design continued by HDS Architects) to be a mixed-use complex with private, market-...
| Aug 11, 2010
Nurturing the Community
The best seat in the house at the new Seahawks Stadium in Seattle isn't on the 50-yard line. It's in the southeast corner, at the very top of the upper bowl. "From there you have a corner-to-corner view of the field and an inspiring grasp of the surrounding city," says Kelly Kerns, project leader with architect/engineer Ellerbe Becket, Kansas City, Mo.
| Aug 11, 2010
AIA Course: Historic Masonry — Restoration and Renovation
Historic restoration and preservation efforts are accelerating throughout the U.S., thanks in part to available tax credits, awards programs, and green building trends. While these projects entail many different building components and systems, façade restoration—as the public face of these older structures—is a key focus. Earn 1.0 AIA learning unit by taking this free course from Building Design+Construction.
| Aug 11, 2010
BIM adoption tops 80% among the nation's largest AEC firms, according to BD+C's Giants 300 survey
The nation's largest architecture, engineering, and construction companies are on the BIM bandwagon in a big way, according to Building Design+Construction's premier Top 50 BIM Adopters ranking, published as part of the 2009 Giants 300 survey. Of the 320 AEC firms that participated in Giants survey, 83% report having at least one BIM seat license in house, half have more than 30 seats, and near...
| Aug 11, 2010
World's tallest all-wood residential structure opens in London
At nine stories, the Stadthaus apartment complex in East London is the world’s tallest residential structure constructed entirely in timber and one of the tallest all-wood buildings on the planet. The tower’s structural system consists of cross-laminated timber (CLT) panels pieced together to form load-bearing walls and floors. Even the elevator and stair shafts are constructed of prefabricated CLT.
| Aug 11, 2010
Integrated Project Delivery builds a brave, new BIM world
Three-dimensional information, such as that provided by building information modeling, allows all members of the Building Team to visualize the many components of a project and how they work together. BIM and other 3D tools convey the idea and intent of the designer to the entire Building Team and lay the groundwork for integrated project delivery.