The UGR is a scale that ranges from 10 to 30. A UGR of 10 represents a low level of discomfort, while a UGR of 30 represents a high level of discomfort. The UGR is calculated based on a number of factors, including the luminaires' luminance, their distribution, the surrounding surfaces, and the observer's position.
What quality classification should be adopted as a minimum for different types of space? European EN standards have been formulated for this purpose. These apply to all European Member States. Standards Institutes are required to adopt the European standards in their national codes. For the Dutch market for example the European standards bear the coding NEN-EN. In Germany this is DIN-EN.
The UGR-L values for a range of spaces are set out in standard NEN-EN 12464-1. UGR-L stands for Unified Glare Rating Limit, the limit for the degree of glare.
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