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.

EN 12464-1 recommends UGRL ≤ 19 for offices, ≤ 16 for precision work and video meetings, ≤ 22 for circulation. Residential design does not use UGR formally but the principle is identical — a bare LED in the field of view is never acceptable.

Fixes lie in optics (micro-prismatic diffuser, deep louvre, honeycomb), a luminaire with a UGR rating and the right position. Linear profiles with an indirect component lower UGR more efficiently than many downlights.

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

Use UGR < 19 fittings certified to EN 12464-1; mix direct and indirect light in large open-plans.

Video meeting rooms

Target UGR < 16, soft direct overhead with vertical face lighting.

Retail & Showroom

Accent spots aimed at the product, not at the customer's eyes.

Residential

Specify louvres, honeycombs or deep reflectors anywhere the source is visible.

Hospitality

Lobby and restaurants UGR < 19; rooms even lower.

Advantages

Less eye fatigue and headaches
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

UGR < 19 for offices and meeting rooms
UGR < 16 for video meetings and precision work
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 measures the comfort of a whole space, not a fitting. Target UGR < 19 for offices, < 16 for demanding work. Residential design has no such norm but the principle holds — bare LEDs in the eye line are never acceptable.

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