Spectrally Enhanced Lighting Feasibility Study
Spectrally enhanced lighting feasibility study in an office environment at the University of California, Office of the President (UCOP) in Oakland, California.
The U.S. Department of Energy (DOE) conducted a feasibility study to evaluate how people would respond to spectrally enhanced lighting (SEL). On this page, you will find a description of the study and key conclusions.
Purpose
Prior to 2001, SEL studies had been limited to laboratory studies conducted at Lawrence Berkeley National Laboratories (LBNL). These studies had demonstrated increased visual acuity and brightness perception under the conditions of full field of view with SEL. However, a prevalent concern among lighting design professionals remained — would people object to the color of SEL lighting?
If SEL were implemented and building occupants rejected the lighting, any energy savings potential would be offset by occupant complaint and the systems would inevitably be replaced. When Pacific Gas & Electric Company (PG&E) retrofit seven buildings totaling 300,000 square feet in 2001, they gathered anecdotal evidence of occupant acceptance of SEL under reduced illumination levels. However, these retrofits were not documented as a formal study and the lighting community did not consider it a reliable SEL test case.
In 2002, a feasibility study was conducted by the DOE, PG&E, AfterImage + Space (AI+S), and Pacific Northwest National Laboratory (PNNL) to evaluate user acceptance of SEL strategies in an office environment. The study was conducted at the University of California, Office of the President (UCOP) in Oakland, California, and the results were published by DOE in 2004.
Description
The UCOP consists of two nearly identical floors in an 11-story office building, each floor measuring approximately 30,000 square feet. The space includes open office areas with approximately 120 office cubicles, and 120 private offices (perimeter and interior). The original lighting in the open office area used pendant indirect luminaires; the private offices used recessed parabolic direct luminaires.
In this study, one floor was re-lamped with new 3500 kelvin (K) lamps (reference lamp) and the other with new 5000K spectrally enhanced lamps. Both new lamp types had a color rendering index (CRI) of 86. Electronic dimming ballasts were installed in the existing luminaires on both floors to adjust the light levels. The reference floor with 3500K lamps (referred to as 835 lamps) had the lighting levels adjusted to approximately the same light level that existed prior to re-lamping. The lighting levels in the offices on the floor with the 5000K lamps (referred to as 850 lamps) were set at approximately 20% lower light levels than the floor with the 835 lamps, in accordance with the SEL design method. The study was designed to determine the energy savings potential of SEL, evaluate occupant satisfaction, and assess the effectiveness of the SEL design method.
Conclusions
- Evaluation of user feedback showed that the 850 lamps can be used at reduced light levels without affecting user satisfaction.
- The energy savings potential due to spectrally enhanced 850 lamps ranges between 17-24% when compared to the 835 lamps. By extension, the energy savings potential of the 850 lamp ranges between 22-30% when compared to the 735 lamp.
- The design method for SEL provides a reliable model for predicting light level differences and energy savings potential.
For all of the details of the study and results, read the full report, 2004 Energy Conservation Using Scotopically Enhanced Fluorescent Lighting in an Office Environment.