Abstract
With conditions for lighting design changing it is becoming important to consider what to do in rooms where there is no particular visual task. The current European standard for lighting in work places gives a number of requirements for room lighting, the most onerous being the requirement for cylindrical illuminance. Mean room surface exitance (MRSE) has been put forward as a metric that is a good predictor of perceived adequacy of illumination. The paper examines the consequences of adopting a proposed MRSE target of 100 lumens per square metre in two sizes of room with a variety of surface reflectances and lit by a regular array of light sources with a range of light distributions. The paper concludes that significant extra luminous flux will be required to meet the new MRSE target and that light distributions with a significant upward component will also be needed.
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