An appraisal of task-ambient lighting systems

Four task-ambient lighting schemes are categorized: luminaires in the ceiling only, indirect torcheres for task lighting alone, task lighting luminaires built into furniture, and task and ambient lighting both provided by indirect torcheres. A photometric appraisal of each of these categories was performed on installations in Canada and the U.S.A. Photometric measurements included horizontal illuminance, equivalent sphere illuminance, contrast rendering factor, luminance and reflectance. Data were also collected on the total power loading per unit area of work space as found in the offices containing the various systems. The results are evaluated in terms of current North American recommended practice with a detailed discussion of each system appraised. It was concluded that none of the systems measured met North American recommended IES lighting levels and the quantity and quality of illumination varied enormously amongst the sample of task- ambient systems investigated. Low ambient lighting levels can significantly affect the overall quality of light and may also require the surfaces of surrounding vertical walls and partitions to be separately illuminated. Nevertheless, it is the opinion of the authors that, if properly designed, task-ambient lighting systems offer significant potential for power savings in office lighting systems.Les auteurs d\ue9crivent quatre modes d'\ue9clairage travail/d'ambiance: luminaires au plafond seulement, torch\ue8res indirectes pour l'\ue9clairage travail seulement, luminaires d'\ue9clairage travail incorpor\ue9s au mobilier et torch\ue8res indirectes pour l'\ue9clairage travail et d'ambiance.Peer reviewed: YesNRC publication: Ye