UGR
UGR and glare: the visual-comfort threshold at work and at home
UGR indicates discomfort glare under specific conditions. It depends on luminaires, room geometry, reflectances and observer position; it does not describe all aspects of visual comfort.
UGR follows the CIE formula combining luminaire luminance, angular size, position in the field of view and background luminance. The value is a room property, not a luminaire property — the same fitting can score UGR 17 in one office and UGR 22 in another.
Glare is direct (source in the field of view) or reflected (off a glossy surface, a monitor). UGR mainly covers direct glare. Glossy materials, glazed walls and badly placed downlights make it worse.
Check the required glare limit for the specific visual task in the current EN 12464-1. A room name alone does not establish a universal limit for every office or video meeting.
Glare depends on optics, luminaire luminance and position relative to the observer. Request photometry and UGR tables with their calculation conditions; a catalogue label or indirect component alone does not establish the result in an actual room.
With Tunable White / biodynamic lighting UGR matters even more — the higher daytime intensity multiplies the glare risk if optics are wrong.
Practical applications
Offices & open-space
Request photometric data and assess the installation in its actual room geometry. A luminaire alone does not demonstrate EN 12464-1 compliance. Combine direct and indirect light according to the calculation and architecture.
Video meeting rooms
For video meetings, assess face lighting and screen reflections. Soft face lighting is design advice; check the glare limit for the actual task.
Retail & Showroom
In shops, assess glare against the visual tasks and applicable workplace requirements. Aim accent spots at merchandise and check the views of customers and staff.
Residential
Specify louvres, honeycombs or deep reflectors anywhere the source is visible.
Hospitality
In lobbies, restaurants and bedrooms, assess source visibility from typical guest positions. Low intensity alone does not rule out glare.
Advantages
- Reduced discomfort glare; a health outcome is not guaranteed
- Better screen comfort
- Stronger perceived quality with low flicker
Limitations
- Lower UGR often means a deeper, costlier fitting
- Value depends on room geometry
- Does not cover reflected glare
Recommendations
- Check workplace requirements for the specific activity in the current standard.
- Consider a stricter design target individually for demanding visual tasks.
- Micro-prismatic or UGR-rated optics overhead
- Linear profiles with deep louvres instead of bare LED
- Honeycomb / dark-light optics in residential where a source is visible
Common mistakes
- Bare point sources in the field of view
- Full-blast open-plan lighting with no layering
- Glossy surfaces facing strong sources
- Downlights directly above the dining or meeting table
- Trusting 'UGR < 19' on a datasheet without checking real geometry
In summary
UGR is one part of lighting assessment. Also check uniformity, reflections, contrasts and observer positions; a catalogue rating does not replace an installation calculation.
Want a quick estimate of the luminaire count? Open the lighting calculator.
Sources
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