What is UGR and how do you avoid glare?

What UGR is

UGR (Unified Glare Rating) estimates discomfort glare in an indoor lighting installation, based on luminaire positions, luminance, the visual background and the observer. It is not a lamp-only figure: it is a system value.

A low UGR means less visual discomfort. In offices, classrooms and healthcare it matters as much as lux: you can meet illuminance and still work poorly because of glare.

How glare happens

Glare appears when high luminance enters the field of view: open optics, downlights seen from a corridor, unshielded linears, or extreme contrast between desk and ceiling. Reflected glare on screens and glossy desks also counts.

Lowering power is not enough: a high-output luminaire with good optics can glare less than a weak, poorly shielded one.

How to avoid glare

• Specify luminaires with optics and UGR suited to the task (microprism, dark light, well-aimed asymmetric).
• Respect mounting heights and spacings from the calculation.
• Avoid bare LEDs; use diffusers or deep reflectors.
• Control luminances on stretch ceilings and glossy surfaces.
• Dim when possible: lower flux means lower luminance.
• Place desks so luminaires are not on the sight line or reflected in the screen.

Frequently asked questions

Is UGR 19 mandatory in every office?

It is the usual limit for screen work under EN 12464-1. Archives or corridors may allow higher values. Zone the building; do not apply one number everywhere.

Can a downlight meet UGR 19?

Yes, if optics, cut-off and layout allow it. Many open downlights are unsuitable for office desks; deep-reflector types can work.

Does UGR apply outdoors?

UGR is for interiors. Outdoors other criteria apply (driver glare, light pollution, G-index by application).

How Celux can help

We manufacture luminaires with optics for office, education and healthcare UGR. If your project needs UGR ≤19, we help choose product and check the installation calculation, not only the datasheet.