KOE Lighting
Qu’est-ce que l’UGR ? Comprendre l’éblouissement et le confort visuel
Qu’est-ce que l’UGR ? Comprendre l’éblouissement et le confort visuel
When choosing lighting, we often look at lumens, wattage, efficiency, and color temperature.
But there is another important question:
Is the light comfortable to look at?
A light can provide enough illumination and still create uncomfortable glare.
This is where UGR — Unified Glare Rating comes in.
What Is UGR?
UGR (Unified Glare Rating) is a method used to describe the potential discomfort glare caused by lighting in an indoor environment.
In simple terms, it helps us understand how uncomfortable bright luminaires may appear within our field of view.
The basic principle is:
The lower the UGR, the lower the potential discomfort glare.
For example, a bright downlight directly in your field of view may feel uncomfortable even when the room has enough light.
UGR helps lighting designers consider this aspect of lighting quality.
Why Does UGR Matter?
Lighting is not only about making a space bright.
People also need to be able to work, read, shop, communicate, and relax comfortably.
Consider an office. A bright luminaire directly above or in front of a person may not prevent them from working, but it can create distracting visual discomfort over many hours.
This is why glare control is particularly important in spaces where people perform visual tasks for long periods.
Enough light does not always mean comfortable light.
Understanding UGR Numbers
UGR is expressed as a number. In general:
Lower UGR = less potential discomfort glare.
Different applications have different requirements. The following values can be used as a simple guide:
| UGR Level | Typical Use | Why It Matters |
|---|---|---|
| UGR <16 | Very demanding visual environments | Very low glare is desired |
| UGR <19 | Offices, classrooms, libraries, computer workspaces | People perform visual tasks for long periods |
| UGR <22 | General commercial, retail, reception, hospitality | Good glare control with more flexibility |
| UGR <25 | Less demanding indoor applications | Visual tasks are less intensive |
| UGR <28 | Some general or short-stay indoor areas | Higher glare may be acceptable depending on the application |
| UGR >28 | Generally unsuitable where visual comfort is important | Higher potential discomfort glare |
These are general reference levels, not absolute rules. The appropriate UGR depends on the function of the space, visual tasks, lighting layout, and applicable project requirements.
Why Do Different Spaces Need Different UGR Levels?
The reason is simple:
People use different spaces in different ways.
An office worker may spend eight hours looking at a screen.
A student may spend hours reading.
A customer may spend only a short time walking through a retail store.
Someone in a corridor may have little need for detailed visual tasks.
The longer and more visually demanding the activity, the more important glare control generally becomes.
What Does UGR Mean to the User?
A lighting designer sees UGR as a technical value.
For the user, it means something much simpler:
Visual comfort.
Lower glare can help create a more comfortable environment for:
- Working — less distracting brightness during long working hours
- Reading — more comfortable visual conditions
- Shopping — a pleasant environment for viewing products
- Dining and hospitality — comfortable lighting without unnecessary visual distraction
- Living at home — a more comfortable environment for relaxing, reading, or spending time with family
This is why lighting quality cannot be judged only by how many lumens a product produces.
The important question is not only:
How much light do we get?
It is also:
How comfortably do we experience that light?
Is Lower UGR Always Better?
Not necessarily.
A lower UGR generally means less potential discomfort glare, but UGR is only one part of lighting quality.
A good lighting solution also needs to consider:
- Illuminance
- Light distribution
- Color quality
- Beam angle
- Energy efficiency
- The function and atmosphere of the space
The goal is therefore not simply to achieve the lowest possible UGR.
The better question is:
What level of glare control is appropriate for this space?
An office, retail store, restaurant, hotel, and home may have very different lighting requirements.
Lighting Is More Than Illumination
Lighting has traditionally been discussed through numbers such as:
Wattage → Lumens → Efficiency
These specifications are important.
But good lighting is about more than output.
It is also about:
Glare → Visual Comfort → Color Quality → Light Distribution → User Experience
UGR is one way to understand this difference.
A well-designed lighting environment should provide the right amount of light, in the right way, for the people using the space.
At KOE, we believe:
Lighting is not only about illuminating a space. It is also about how people experience that space.
Understanding UGR is one step toward better lighting.