Lights are a part of our lives, we use them at home, at work, or in our free time. Because of that, lighting has to be confortable, usefull and pretty.
Maybe you have never heard about UGR, but it’s so important in work enviroments that for sure you will. Want to know why, keep reading!
What’s the Unified Glare Rating (UGR)?
If you want to know how likely a luminaire is to cause discomfort to those around it, UGR rating will helps you to do it.
The UGR is a value, a parameter which provides information about the degree of pychological glare of a lighting installation in an indoor space. This value is defined within a scale of 10 to 30.
In the 70’s, each country used different methods to measure the glare. But in 1995 the CIE (Internationl Comission on Illumination) published a recommendation to keep the UGR method like a base of the glare limitation.
This method is a mix of two of the european systems until this moment, Söllner curves and the IES method. The difference between these and the UGR, is that the UGR keeps in mind surfaces glare and light radiation in every direction.
However, the Söllner method just only takes into account the linear and transverse direction of the lights.
Glare is a common problem in workplaces. Inappropriate lighting causes excessive brightness which reflects in surfaces such as computer screens, whiteboards, windows, etc. It may cause disruption for people like headaches and eye trouble.
How to calculate the Unified Glare Rating Value?
UGR is calculated by using an equation which takes a number of factors that may contribute to reflection caused by a luminare, such as the angle, the desired of glare and the luminance value (lumen output).
UGR = 8 log {0,25/Lb Σ L2 ω / P2}
There are two methods to reduce the glare: use luminaires with URG < 19 rated to ensure that the lighting design is apropriate for the enviroment in which they are going to be used, and the correct number and position of luminaires.
Tabular method.
The tabular method determine the UGR value of a lighting in a room. The designers must keep in mind this method to choose the best luminaires.
The tabular method says that the floor has a maximum degree of reflectance of 20%, walls from 30% to 50% and the ceiling from 50% to 70%. White walls or ceilings have a degree of refectance from 75% to 90%.
Conclusion.
UGR system simplifies the lamps election more than the old Söllner system, because allows it to automate the calculation in a lighting calculation sofware, or select the luminaire using the UGR table.
Below you can find the perfect Unified Glare Rating for each enviroment.
UGR ≤ 16. Technical drawing
URG ≤ 19. Office works such as reading, writing, meetings.
URG ≤ 22. Craft and light industries.
URG ≤ 25. Heavy industry.
URG ≤ 28. Foyers.
What do you think abour UGR? Did you hear about UGR before?