Livingroom light up with Focus track micro pendant from Hide-a-lite.

UGR (UNIFIED GLARE RATING)

WHAT IS UGR AND IS IT CALCULATED?

The UGR method is used to calculate the degree of discomfortable glare in a symmetric indoor facility. Calculating according to the equation below,
a Unified Glare Rating (UGR) can be arrived at.

But don’t worry about this equation.
We calculate it for you.

Explanation of the concept UGR.

CAN A LUMINAIRE HAVE A UGR VALUE?

No, the UGR value does not belong to the luminaire but rather involves the its illuminating surface and the ambient light in relation to the observer’s eye and its position and angle. 

A rule of thumb is that intensive luminaires in dark surroundings give a higher UGR value while intensive luminaires in light surroundings give a lower UGR value.
 

Figure 1 Example of differences in contrast between dark and light backgrounds.

Differences in contrast between dark and light backgrounds

WHICH UGR VALUE SHOULD BE MET?

In the European standard, EN 12464-1:2011, there are UGR requirements for various visual tasks based on their difficulty, the recommended glare figures for UGR are provided in tables based on the task involved. UGR tables are provides in steps of 3, where 1 step is barely noticeable while 3 steps is perceived as a clear change in the glare. 

It is the level of difficulty in the visual task that determines what UGR requirement the workplace /room is given. Below is a simplified recommendation table, excerpts from the standard.
 

So the higher the requirement, the lower the UGR value!
Ref. no. UGRL Examples of area, task or activity
5.26.3 UGR16 Office: Technical drawing work
5.26.2
5.26.5
UGR19

Office: Writing, typing, reading, data processing
Office: Conference and meeting room

5.2.1 5.27.1 UGR22 Common spaces in buildings: Cafeterias, serving rooms 
Retail trade: Sales area
5.2.4 UGR25 Common spaces in buildings: Cloakrooms, washrooms, bathrooms, toilets
5.1.1 UGR28 Communication areas: Communication areas and corridors

WHAT AFFECTS THE UGR VALUE IN A FACILITY?

A room has certain conditions that can’t always be influenced but nonetheless have an effect on UGR value.

  • Ceiling height/installation height
  • Room size
  • The ability of surface colour and material to reflect light

(See the standard values for reflectances on ceiling/wall/floor in the Light Template Indoors p. 8)

HOW CAN I AFFECT THE UGR VALUE IN A FACILITY?

You can affect the UGR value with the choice of luminaire and lighting. 

Tip!

  • Choose well dimmed fittings with hidden light sources or with anti-glare devices (feel free to evaluate visually)
  • Increase the luminosity of the room’s walls by illuminating them
  • Increase the luminosity of the ceiling by using luminaires with uplight