The Carrollton-Farmers Branch Independent School District (CFB) in Carrollton, Texas, invited the U.S. Department of Energy (DOE) to conduct a GATEWAY evaluation of a trial installation of tunable-white LED lighting systems in several classrooms. The classrooms included a fifth-grade math and science classroom at Dale B. Davis Elementary School (DES), a fourth-grade reading and language arts classroom at Sheffield Elementary School (SES), and an eighth-grade science laboratory at Charles M. Blalack Middle School (BMS).
The trial installation used lighting and technology from lighting company Acuity Brands. The Pacific Northwest National Laboratory conducted the study on behalf of the DOE. The consulting engineering firm Estes, McClure & Associates, working in collaboration with the manufacturer Acuity Brands Lighting designed the tunable white lighting system.
Specifically, the school district wanted to evaluate the potential for tunable lighting to enhance teacher engagement with students and improve student performance.
Back to School
The LED lighting systems were installed in August 2016, just before the beginning of the 2016–2017 school year. In the particular classrooms, each recessed fluorescent luminaire was replaced with a 2′ x 4′ Lithonia Lighting® BLT Series Tunable White LED luminaire from Acuity. The luminaires were specified with a curved diffuser with linear prisms and with Acuity Brands nLight® nTune™ control interface.
The LED luminaires provide tunable white lighting with a CCT range of 3000–5000 K. The 4800-lumen light-output option was specified for the classrooms. This specified output resulted in a rated light output ranging from 4600 to 5000 lumens from an input power of 34–45W at full output.
The lighting control system offered the ability to alter the spectral power distribution (SPD) across four preset conditions, associated with nominal CCTs of 3000 K, 3500 K, 4200 K, and 5000 K. Also, preset scene controls could vary the on/ off status and dimming level of different luminaire zones within the room, to better support classroom uses such as audiovisual presentations and student speeches.
The reduction in input power for the tunable-white LED lighting system was estimated to be about 58% compared to the fluorescent lights that were replaced in the classrooms.
All the Teachers Used Dimming or Turned off Sections of Lights
According to the monitoring system, the individual teacher’s use of the controls ranged widely. However, in each case, all or some of the luminaires were turned off or dimmed for portions of the school day. They also found that when control locations were more easily accessed by the teacher, the dimming level was varied more regularly.
The LED lighting systems were installed and commissioned with very few difficulties, and any issues with initial performance were quickly resolved. The three teachers used the scene controls regularly during the school day but used the SPD controls infrequently.
During DOE interviews with two teachers, the teachers expressed appreciation for the ability to customize the lighting to meet different classroom needs. The teachers also felt that the lighting and controls let the students to be engaged in choosing the settings for various classroom activities.
Both teachers stated that the lighting system enhanced the overall learning environment. However, unfamiliarity with CCT and other lighting metrics prevented the teachers from fully taking advantage of such lighting in the classrooms. Additionally, the DOE found that labeling lighting control settings with familiar terms may provide additional barriers to full usage of the controls.
Teachers did not Use “Reading”, “Testing”, and “Energy” Settings
Despite the fact that the project offered labels including “Reading”, “Testing”, and “Energy” in the expectation that they would be self-explanatory, the teachers did not use these settings.
While the ability to dim and turn off sections of lights while not in use does tend to save electricity, the ability to alter the quality of light does not necessarily do so.
More education about the potential and the latest research for the teachers would likely be helpful in getting users to maximize the potential of using the lighting to help enhance learning and performance of students.