High Performance Lighting Controls in Private Offices: A Field Study Of User Behavior And Preference

A lighting controls study performed over a three month period provided data that can be used to determine the impact of manual switching and dimming controls on occupant behavior and attitudes and on energy use. Data were analyzed for 58 private offices on a single floor of a modern office building in Boulder, Colorado. Each office was equipped with a ceiling-mounted infrared motion sensor, a dimmer-switch at the door, and a portable dimmer-switch at or near the computer monitor, which controlled two 18-cell parabolic luminaires with three-T8 lamps and electronic dimming ballasts. Occupancy and energy data were collected using a data acquisition system, observations were made of occupant tasks and window blind usage, and surveys were conducted to measure occupant attitudes and preferences toward lighting controls. The results show that: 1. Occupants highly value windows and window blinds. 2. Occupants typically use window blinds to occlude direct sunlight while allowing daylight to enter the office. 3. Occupants in offices with northern exposures are more likely to keep their blinds at least partially open and their lights off. 4. Occupants highly valued dimming and preferred to have a lighting control at their workstation. 5. Seventy-four percent of occupants dimmed their lights during the course of the study. 6. Occupants did not typically adjust lighting levels when they changed tasks. 7. Occupants liked having manual controls and accepted automatic controls as long that did not interfere with their activities. 8. Occupants did not notice when lighting returned automatically to previously set levels when they reentered the room, but when asked, said that they would prefer this feature. 9. Energy use was reduced by 61% by motion sensors and manual switching and dimming controls.