A case study on occupant controlled lighting in offices

Asta Logadóttir

Research output: Contribution to book/anthology/report/conference proceedingConference abstract in proceedingResearchpeer-review


Occupant controlled lighting is known to present opportunity for energy savings1,2,3,4 and can increase occupant satisfaction with the lit environment5, 6, 7, 8, 9. Scale model and Laboratory studies suggest that the illuminance interval and the starting value provided to occupants to adjust from, have an effect on the illuminance settings chosen by the occupants 10. The illuminace interval limits the possibilities of choices and the chosen illuminances tend to be
distributed in all parts of the illuminance interval. This results in the mean value of illuminance settings to approach the middle of that specific interval 11,12. The starting values act as anchors for the illuminance choices, meaning that low starting values tend to result in lower illuminance settings then high starting values6, 11, 12. The influence of illuminance interval and start value is considered in this case study on occupant controlled lighting in offices with
focus on energy savings and occupant satisfaction.
The case study was performed in a pharmaceutical company in Måløv, Denmark where the lighting installation was renovated in a two person office and a four person office in 2013. The fluorescent tubes were replaced with DALI controllable LED luminaires and each employee was given a task light on their desk providing 592 lx, U0 = 0.5 on the task area (60 x 60 cm2) and 87 lx, U0 = 0.2 on the surrounding area, when turned on.
The lluminance intervals started from zero to the maximum of 50, 100, 200 and 500 lx with U0=0.5. The starting values were the minimum and the maximum of each interval and every interval with the different starting values was presented to the occupants in a randomized order for a total of one week. The CCT was 3000 K and the illuminance settings data was monitored online by collecting the DALI signals to the LED luminairs and the use of task light was registered by continuously measuring their power consumption. The test was performed
from January to March 2014 and the weather conditions were mostly overcast sky. The occupants were informed that the lighting in their offices was being tested and at the end of each week they were asked to answer an online questionnaire about their satisfaction with the office lighting. They were further notified that they, at all times, were allowed to adjust the lighting in their office to their preference. One of the two offices reported the lighting system
to malfunction when the 0 – 50 lx interval was provided, they were thereby provided with an interval of 0 to 100 lx in order to support their working environment. The adjusted illuminances for the high start values were 50 lx, 100 lx, 200 lx and 455 lx for respective maximum illuminance of 50, 100, 200 and 500 lx. The low start values resulted in illuminance settings of 50 lx, 83 lx, 163 lx and 193 lx. The energy use of the LED system is compared to the previous installed power of 80W for fluorescent tubes in each office. The illuminance settings led to 80% savings for the maximum 50 lx interval, 70 % savings for the
100 lx interval, 50 % savings for the 200 lx interval and for the 500 lx interval the savings was 50 % for a low starting value but the savings were negative by 17 % when the starting value was high.
The occupants of the two person office only operated the task light when the interval provided a maximum of 100 lx, starting at a low starting value. The occupants of the four person office operated the task light 65% of their working hours when provided with a low starting value and 48% of the time when provided with high starting values. The average satisfaction ratings indicated that the occupants were most satisfied with the maximum 200 lx interval; this applies for both high and a low starting value. The interval with a maximum of 500 lx provided the most satisfied occupants and the most unsatisfied
The results of this case study can be used as an argument for further exploring the potential that lies within occupant controlled lighting for energy saving and occupant satisfaction as the results from the limited amount of subjects in this study support the laboratory findings for occupant controlled lighting. Low starting values within a limited illuminance interval may provide satisfied user of energy efficient occupant controlled lighting.

Original languageEnglish
Title of host publicationProceedings of the 28th Session of the CIE, 28 June – 4 July 2015, Manchester, United Kingdom.
Number of pages2
Publication dateJun 2015
ISBN (Print)978-3-902842-55-8
Publication statusPublished - Jun 2015
Event28th CIE Session - Manchester University, Manchester, United Kingdom
Duration: 28 Jun 20154 Jul 2015


Conference28th CIE Session
LocationManchester University
CountryUnited Kingdom


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