Are designers keeping up?
April 13, 2012 1 Comment
BS EN 12464-1, Light and Lighting, Part 1 indoor workplaces, was first published in 2002. It included a schedule of recommended minimum task illuminances for a range of industrial, institutional and commercial applications. These values were similar to those previously in the Society of Light and Lighting Code. Originally the SLL values were ‘general’ illumination for the complete floor area thus enabling equipment and workers to be positioned anywhere in the space. A convenience when electricity was cheap.
However the BS specifically refers to ‘task’ illumination, normally only a small part of the gross floor area. The rest of the room would require less illuminance and thus considerable capital and operating cost savings can be made. But where are the task areas? Often the client has no idea when the lighting design is carried out. The designer then has to revert to ‘general‘ illumination to guarantee adequate lighting of the task. However the client will pay for the over lighting of the ‘non-task’ areas.
This problem of insufficient information is compounded by the changes included in the revision to BS EN 12464-1 last year. Introduced for the first time is the requirement for mean cylindrical illuminance in the space to provide good visual communication and recognition of objects. This should be no less than 50 lux, and for areas where good visual communication is important like offices, meeting and teaching areas not less than 150 lux. Although the concept of cylindrical illumination is not new it has not been widely considered for the routine lighting of workplaces.
How do many existing lighting schemes meet these new requirements? Very few published photographs of interiors include a full complement of ‘workers’ so there is little subjective evidence of how modern lighting affects the appearance of the human face. Accurate measurement could be a problem. Added to this is the same problem outlined above, the lack of occupational information of the space.
The Standard only considers the requirements of ‘workers’ so places where customers or visitors dominate lighting requirement need to be considered separately.