What is UGR?

What is UGR? And why it's important?

UGR is short for Unified Glare Rating. It is an objective measure of discomfortable glare produced by a luminaire when introduced to an environment. Generally, it ranges from 40 (extremely high glare, intolerable discomfort) to 5 (very low glare, no perceived discomfort). The higher the UGR number the higher the glare from the luminaire and the increased discomfort for office workers.
UGR is getting more and more noticed by light designers because inappropriate glare affects us in many ways such as discomfort and potential side effects such as eye-trouble, headaches, disruption, poor concentration and less productivity in the workplace, poor customer experience etc.

How is UGR Calculated?

UGR is calculated by using the above equation which considers several factors, such as background luminance, average luminaire luminance and solid angle, and displacement from the line of sight.
The above equation was meant to offer you a rough idea about how it is calculated. But no worries on the detail calculation, normally architects and the light manufactures will provide it to you.

Which UGR value should be met?
In the European standard, EN 12464-1:2011, there are maximum UGR requirements for various visual tasks based on their difficulty. The standard lists more than 280 different types of work areas in almost every type of working environment. With the best of intentions, a lighting designer could select fittings and design a lighting scheme to deliver a specific UGR value.
And in offices, the recommended UGR limit is 19.

UGR19 is not a property of the luminaire, but a measurement for an installation.
Contrary to widespread opinion, UGR is a measurement for an installation, not for a light fitting. So strictly speaking, there is no such thing as a ‘UGR19-compliant’ luminaire. However, Luminaires can be manufactured to reduce glare, as you could see UGR<19 in many datasheets, and these low glare light fittings help support a UGR19 compliant lighting scheme.

How do we find the UGR values of a product and detect whether it is“UGR<19” or not?

People use tabular method to determine the UGR value of a lighting, where the luminaire would have in a room with the dimensions of 4H/8H and degrees of reflectance of 20% for the floor, 50% for the walls and 70% for the ceiling.
And there is a table to help.
Take Cyanlite's LED Backlite Panel for example.

1st Step: Open the IES file (Goniophotometer test report). On the first page, you could see it’s 33.1W and over 125lm/w. Quite nice, right?

2nd Step: Nove let’s move to the UGR table and navigate to 4H x 8H Room Dimensions and the UGR value will be in the first column (under a standard room reflectance of 0.7/0.5/0.2).

This panel is UGR<19.

And Cyanlite can make it up to 7250 lumen output while more than 115 lm/w and UGR<22.(See below report)

Cyanlite, as the expert of LED panel lights, provide the full solution for both backlite and sidelight LED panels for:

• different application requirements: IP20/IP65/with air vents/built-in sensors/customized sizes;
• different ceiling systems: Lay-On/Lay-In/Metal ceilings/Plasterboard ceilings;
• different installations: Lay-On/Recessed/Surface Mounted/Suspension;

Contact Cyanlite to get more details of our 5-years warranty premium product and quotation.

Cyanlite LED panel light selection guide[3.9 Mb PDF]