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Unified Glare Rating (UGR)



UGR (Unified Glare Rating) is the method that calculates the glare from luminaires, light through windows and bright light sources.


The UGR rating helps to determine how likely a luminaire is to cause discomfort to those around it. For example, this may be the discomfort that a LED Panel may possibly cause to workers in an office. This classification ranges from 5 to 40, whereby the lower the number, the lower the glare.


Light glare can prove to be a common problem in the workplace. Inappropriate luminaires cause excessive brightness to be “bounced off” reflective surfaces, such as computer screens, projectors, glass doors and whiteboards etc. This can cause disruption for the occupants of offices, in terms of headaches & eye trouble, which can then lead to employee absences. This can also prohibit employee concentration.


UGR is calculated by using an equation which takes into account a number of factors that may contribute to glare caused by a luminaire. This can be factors such as the angle of the luminaire, the likelihood of glare and the luminance value (lumen output). The equation that is used to calculate the UGR is:


L= The luminance value of the luminaire

Lb= The value of the background luminance

ω= The solid angle of the luminaire that is seen by the viewer

p= The Guth Index. Based on the likelihood of glare, also known as Visual Comfort Probability Σ= Shows that the equation (shown above) includes all the fittings located within the area.


There are two methods to reduce the glare seen when it comes to interior lighting. Firstly, to use luminaires that are UGR<19 rated; secondly to ensure that the lighting design is appropriate for the environment they are being used in i.e. the correct number and position of luminaires.


Within an office setting, for the luminaire to be classified as “low glare” it must have a UGR below 19 at desk level. Any glare level above this rating may otherwise cause discomfort to office workers – this further enforces the need for high quality interior lighting that is rated UGR<19.


There are a number of different UGR limits that should not be exceeded in certain environments, these include:


(UGR Rating / Environment)


UGR ≤ 16 Technical drawing

UGR ≤ 19 Reading, writing, training, meetings, computer-based work

UGR ≤ 22 Craft and light industries

UGR ≤ 25 Heavy industry

UGR ≤ 28 Railway Platforms, Reception Areas

The UGR of the Blindspot is 16. To view catalogue click here

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