A field study of occupant controlled lighting in offices

Abstract

A study of 14 open-plan offices equipped with occupant controlled general lighting recorded achieved workstation lighting conditions at a number of times of the year. The results confirmed the occurrence of a wide range of workstation lighting levels, many significantly below CIBSE Code recommendations, with average electrical loadings due to lighting in the order of 55% of maximum. System con-figuration had a significant influence on luminaire output, illuminances and energy consumption. In general the lowest luminaire outputs were in buildings where the default reset level was to a low output, with the highest outputs being in buildings having high reset levels and large control groups. In addition locally sited control devices were associated with lower luminaire output.

Occupant use of switching and dimming controls in offices

“…Specifically, 27 percent of participants in the Dimming Control condition choose to work above 500 lx, but only 7 percent choose to work below 300 lx. This divergence at low illuminances may be a matter of the greater contribution of daylight in one study 6 and the higher minimum illuminance in the other. …”

“…Similar results have been found in field studies where stepped or continuous dimming is available. Moore et al 6 reported that in their study of fourteen offices in the UK, 60 percent of occupants had chosen to work at an illuminance below 300 lx in winter and 43 percent chose to do so in summer. Only 17 percent chose an illuminance above 500 lx in winter and 30 percent did so in summer.…”

“…Switching off, or leaving the lighting off, is unlikely when control is not local, but are observed for local control. 5,6 In addition, where some of the workstations have daylight for at least some of the time there is a possibility of manual daylight harvesting if those individuals choose lower illuminances in the presence of daylight, as some evidence suggests they will. 10 …”

“…[5][6][7][8][9][10] This paper reports the illuminances chosen by participants in a field simulation study in which two experimental conditions allowed individual control, 11 and uses comparable data from other studies to address several questions. Specifically:…”

Occupant preferences and satisfaction with the luminous environment and control systems in daylit offices: a literature review

“…The above study was followed by a third investigation two years later, from January to March, which included a questionnaire administered to the occupants to investigate luminous conditions and user attitudes toward the lighting control systems [56][57][58]. Seven of the 14 UK office buildings visited incorporated user-controlled lighting (191 respondents), whereas seven had no user control (161 respondents).…”