What is Unified Glare Rating and what should I know?

Liht.uk Thorn Omega + Eaton Crompack LED

Wondering what the Unified Glare Rating means in a product data sheet? Is it important and should you consider it? Here’s your answer…

As we know excessive glare can cause eyestrain and contribute to headaches, it is important to reduce direct glare and reflected glare within an office environment.

Therefore we need to take into account reflections from interior surfaces and from the lights themselves. The Unified Glare Rating (UGR) is used as a measure of glare from all visible lamps divided by the the background lumination of the room.

The European Standard EN 12464 regulates the lighting of indoor workplaces, with values of UGR ranging from 5 to 40 with the lower number being better:

UGR < 13 – the glare is discreet and will go unnoticed

UGR > 28 – will certainly cause a distraction

Generally the UGR values are defined in steps of 13, 16, 19, 22, 25 and 28. The UGR limits of lighting products for various environments that should not be exceeded are:

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, foyers

Appropriate luminaire positioning and high quality optics can all help to reduce glare, so before purchasing a product it is advised to choose a product that has an appropriate UGR level listed in the product data sheet.

This listed UGR value from the manufacturer is generally in regards to a typical reference situation: room dimensions of 4H / 8H with levels of reflectance of 20% for the floor, 50% for the walls and 70% for the ceiling.

In many luminaire data sheets the listed UGR value shown should not be taken as a property of the product itself, unless further details are provided by the manufacturer, as in real life installations this value could be lower or even higher. The value taken from the data sheet should only be used as guidance and for comparison of quality between other units.

For installations where achieving a low UGR is critical, it is always highly advised that a full lighting design should be carried out to determine glare values of all luminaires within that room.

Interested to find out more about what you need to consider when purchasing an LED product? Have a look at our LED Lighting Guide.

Click here for products we supply with reduced levels of glare.

If you need any other guidance then feel free to contact us, we’re happy to help!