UGR stands for Unified Glare Rating and says how much glare a fixture causes. The scale runs from 10 to 28, and lower is better. For office work the standard asks for UGR 19 or lower. Our Nova panels sit below 16.
What is being measured
Glare is not the same as a lot of light. It is about the contrast between the bright fixture and the darker surroundings. A panel pushing 4,200 lumens through a milky sheet is one big bright plane in an otherwise calm ceiling, and that is exactly what tires your eyes when you sit under it for eight hours.
The UGR figure sums that up in one number. It takes in the brightness of the fixture, the size of the light emitting surface, the brightness of the background and the angle you look at it from. A difference of three points is the step at which people actually notice a change. So between UGR 22 and UGR 19 there is a noticeable difference, between 19 and 18 hardly any.
Where the requirement comes from
The European standard for indoor workplace lighting is EN 12464-1, whose current edition dates from 2021. Per task it sets three things side by side:
- Illuminance: 500 lux on the working plane for office work with a screen
- Glare: UGR 19 at most
- Colour rendering: Ra 80 minimum, and Ra 90 where colour genuinely matters
Note the words working plane. Those 500 lux apply to the area where the work happens, not to the whole floor. In the zone around it a step lower is allowed, so 300 lux. In practice that saves fixtures, because you do not have to light a warehouse aisle to office level.
At home the standard does not apply. But anyone fitting out a study and sitting there for hours every day would do well to keep the same numbers. The difference between a cheap panel and one with a low UGR is exactly what you notice over long use.
How a low UGR is achieved
Two ways of building, two outcomes. In a back-lit panel the LEDs sit behind a diffusing sheet and the whole surface lights up evenly. That gives a lot of lumens per euro and an even look, but the entire plane radiates and you notice when you look straight at it. Our Europa 120x30 is built that way: 30 watts and 4,050 lumens, fine for a store room, a hallway or a workshop.
In a louvre panel there is a grid or prism in front that aims the light downward and shields the shallow angles. Directly under the panel you see the same thing, but out of the corner of your eye it is far calmer. That is how the Nova 60x60 is built, with 30 watts, 4,200 lumens and UGR below 16.
Below 16 is comfortably inside the limit of 19. That is not excess: the standard is a ceiling, not a target, and above a meeting table or a desk the margin works in your favour.
How many panels do you need?
This is where it often goes wrong, because lumens at the fixture are not the same as lux on the desk. Part of the light disappears into walls, ceiling and dirt. A lighting calculation therefore uses a utilisation factor for the room and a maintenance factor for ageing.
Roughly, with a utilisation of 0.6 and a maintenance factor of 0.8: for 500 lux in an office of 20 square metres you need around 20,000 lumens of fixtures. That is five panels of 4,200 lumens. Calculate only 500 lux times 20 square metres and you land on 10,000 lumens, out by a factor of two.
The difference between lumens and lux is explained further in What is the difference between lumens and lux?
In short
Look at UGR as soon as people work under it for long stretches. For a hallway, a warehouse or a garage a back-lit panel is fine and you are paying for nothing extra. For an office, a study or a treatment room, UGR below 19 is the line and a louvre panel is worth the money. Both are at LED panels, with the dimmable Nova for anyone who wants to be able to take the light back.
What is a good UGR value?
For office work, 19 or lower, under EN 12464-1. Below 16 is comfortably clear. For a hallway or storage space the standard sets no strict requirement.
Is a low UGR useful at home too?
In a study, yes, because you sit under the same light for long stretches there. In a hallway or store room you barely notice it and you pay for something you do not use.
Why does not every panel have a UGR figure?
Because measuring costs money and only makes sense on fixtures designed for it. If a back-lit panel gives no figure, assume it is above 19.