How is UGR evaluated, and how can I read values?
UGR, or Unified Glare Rating, is the industry’s standard for assessing visual discomfort caused by luminaires. It plays a key role in office, educational, retail, and technical environments where focus, task clarity, and ambient comfort are essential. Generally, a lower UGR value indicates reduced glare and improved visual comfort.
Understanding the 4H × 8H evaluation room
To evaluate glare consistently, UGR calculations rely on a standardised setup known as the 4H × 8H room, defined in EN 13032-1 and EN 12464-1. Here, “H” represents the vertical distance between the luminaire and the working plane, typically 0.75 to 0.85 metres above floor level. Based on this, the room is defined as four times H in width and eight times H in length. Additionally, reflectance values are fixed at 70% for ceilings, 50% for walls, and 20% for floors. This setup ensures consistency across photometric evaluations.
How to interpret UGR tables in LDT files
Most photometric files include a UGR table, which presents values for various room indices and viewing angles. For meaningful analysis:
- Refer to room indices between 1.25 and 2.5, which represent common architectural conditions
- Focus on viewing angles between 30° and 60°, aligning with natural user sightlines
- Take the highest UGR value in that range as your reference point for glare evaluation
UGR requirements for different spaces
According to EN 12464-1, the recommended maximum UGR value varies by application. For instance, visual task areas require stricter limits than corridors or stairwells. The most commonly applied thresholds include:
- UGR < 16 – control rooms, laboratories, and inspection areas
- UGR < 19 – offices, classrooms, and technical task zones
- UGR < 22 – general ambient lighting for corridors and public spaces
- UGR < 25 – low-priority areas such as staircases or storage rooms
Example: Tre’s UGR performance
The Karizma Luce Tre luminaire offers excellent glare control, supported by deep optical design, black louvre, and narrow beams. In standardised UGR conditions, Tre achieves:
- UGR < 8.0 – with a 15° beam
- UGR < 11.6 – with a 30° beam
- UGR < 14.7 – with a 45° beam
Engineered for glare control
Tre belongs to a more prominent family of low-glare linear luminaires designed specifically for professional applications. Alongside Tre, the collection includes Sei, Dodici, and Diciotto, each offering the same optical approach in different sizes. Additionally, the track-mounted versions—Dodici Track, Diciotto Track, and Ventiquattro—allow for seamless integration in dynamic commercial or educational interiors.
Each product in this range helps lighting designers meet UGR targets without compromising performance or layout flexibility. When comparing UGR values, remember to focus on realistic room conditions and avoid relying on the lowest number in the table. If you need help selecting the correct configuration or verifying UGR compliance, contact us — our team is here to support you.
