Light loss factor: IES versus manufacturer recommendations

Engineers should understand appropriate light loss factors, as recommended by the Illuminating Engineering Society.

08/27/2014


The lighting industry has agreed that the minimum life of an LED luminaire shall be at least 70% lumen maintenance (IE: L70) at 50,000 hours of operation. Based on these standards, the Illuminating Engineering Society (IES) recommends using a light loss factor of not more than 0.7. However, some manufacturers identify products as having hours of operation longer than 50,000 hours. Others indicate that their luminaire will have 90% lumen maintenance (L90) for more than 50,000 hours. A few manufacturers recommend a light loss factor to use in calculations for their product.

In these cases, what is considered an appropriate light loss factor? It boils down to individual judgment based on the application of the LED luminaires, the lighting requirements of the space, and the level of confidence in the manufacturer’s data. As it is unlikely that most LED products on the market have been fully tested to their rated life to prove their output, it seems reasonable to err on the side of caution. The ultimate light loss factor selected for a given LED luminaire will have a direct impact on its evaluation when compared to other sources.


Brian Fiander is an electrical engineer at Harley Ellis Devereaux specializing in lighting design and specification. He serves as one of the firm’s sustainable design champions, acting as a resource for other staff members regarding green design, LEED certification, lighting, and electrical systems. He has participated as a panel speaker for the IES Detroit chapter on LED installation and application due to his understanding and specification of LED luminaires.



Product of the Year
Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
40 Under Forty: Get Recognized
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
MEP Giants Program
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
November 2018
Emergency power requirements, salary survey results, lighting controls, fire pumps, healthcare facilities, and more
October 2018
Approaches to building engineering, 2018 Commissioning Giants, integrated project delivery, improving construction efficiency, an IPD primer, collaborative projects, NFPA 13 sprinkler systems.
September 2018
Power boiler control, Product of the Year, power generation,and integration and interoperability
Data Centers: Impacts of Climate and Cooling Technology
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
Safety First: Arc Flash 101
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
Critical Power: Hospital Electrical Systems
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
Data Center Design
Data centers, data closets, edge and cloud computing, co-location facilities, and similar topics are among the fastest-changing in the industry.
click me