Unified glare assessment index (UGR)
The assessment of unpleasant glare in rooms and workplaces involves comparing the Unified Glare Rating (UGR) determined in the lighting design with the limit value (maximum acceptable glare) of this parameter, in accordance with EN 12464-1. It is therefore assumed that unpleasant glare is limited if the UGR requirements are met in the lighting design. However, even such an assessment is not performed, as the employer usually does not have documentation of the lighting design. Thus, glare is not a parameter to be monitored and assessed objectively in the working environment, mainly due to the lack of a standardised measurement method and measuring device. However, such an assessment should be carried out to check compliance with the provisions of 26.2, 39.1 and 40.1 of the Decree of the Ministry of Labour and Social Policy on general health and safety regulations.
Lb - background luminance, L - luminance of the luminous parts of each luminaire towards the eye of the observer, w - solid angle of the luminous parts of each luminaire towards the eye of the observer, p - Guth's position index for each individual luminaire, which refers to the position of the luminaire relative to the line of sight.
The index takes values from 10 to 30.
UGR and perceived discomfort
10 not noticeable
13 barely noticeable
16 noticeable
19 acceptable
22 unacceptable
25 barely tolerable
28 unbearable
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