Unified Glare Ratings (UGR) Explained
When planning interior lighting in commercial spaces, it is critically important to provide sufficient brightness for functionality and design, while at the same time preventing excessive glare – which can cause discomfort and potentially create safety risks.
A Unified Glare Rating (UGR) is a way designers can assign a value to the amount of glare likely to be experienced in an environment based on information about the luminaires, the room, and the likely position of observers. Understanding how UGRs work can help you select products and plan successful lighting layouts, and here we’ll break down the different elements and how they relate to luminaire design.
The impact of glare
Glare occurs when excessive brightness within a person’s field of vision causes visual discomfort. It can come from luminaires, natural light, or reflections. Sensitivity to glare varies by individual, with effects ranging from mild distraction to significant discomfort, impaired vision, and reduced well-being.
Calculating unified glare ratings
UGRs are a numeric score with a practical range of between 10 and 30. The score is calculated for an environment or room, with 10 indicating no perceptible glare and 30 indicating very high levels of glare. Various standards organisations worldwide set guidelines for acceptable levels of glare in building and design, including the Australian Standards: AS/NZS 1680, which reference glare levels of between 13 and 28. The activities being undertaken in an environment determine what level of glare control and UGR rating may be required. A UGR of <19 is a common compliance standard for office spaces, and luminaires with a low glare design often describe themselves as meeting this target.
- UGR 13 Excellent Glare Control
- UGR 16 Good Glare Control – Suitable for areas where glare may cause discomfort and impede careful work
- UGR 19 Moderate Glare Control – A standard for areas where glare should be controlled, such as schools, offices, lecture theatres, and control rooms
- UGR 22 Poor Glare Control – Suitable for areas such as food preparation, assembly shops, machine and tool shops etc.
The calculation to determine UGR uses information about the number and strength of luminaires, the luminance of the background, and the angles and distances involved between light sources and observers. Modern lighting design software such as DIALux, AGi32, and ReLUX, help designers determine UGRs in complex conditions involving multiple luminaires of different types and strengths.
According to the UGR calculation, glare is worsened by:
- Brighter luminaires
- A closer distance between luminaire and observer
- The luminaire being more directly in the observer’s line of sight
- The luminance of the background, with a darker background increasing UGR due to increased contrast
Luminaire design and UGR
If UGR Calculations include information about the room, how can a luminaire be marketed with a UGR?
While UGR considers both the luminaire and its environment, Ektor helps specifiers by providing estimated UGR values based on sample room conditions. This allows designers and facility managers to assess whether a given model will contribute to better viewing comfort by reducing glare.
Elements of luminaire design that can contribute to a lower UGR include:
- Recessed luminaires
A luminaire with a recessed light source has a tighter beam angle, which in many cases reduces the likelihood it will be in an observer’s line of sight. In the case of downlights, for example, a tighter beam angle means that when the light source does enter the line of sight of an observer, it is likely to be at a sharper angle above them and the impact of glare is reduced. - Reflectors
Reflector material can play a part in reducing glare, with polished reflectors more likely to create glare than a matte surface. Likewise certain reflector designs, such as louvres, can be used to reduce glare by restricting the beam angle from part of the luminaire. - Diffusers and luminaire surface area
A light with a small origin point has a greater luminous flux or perceived brightness than one where the same luminance is emitted from a greater surface area. Diffusers work by increasing the visible surface area of the light source, thus reducing glare. Diffusers can also incorporate texture to further disperse and soften light. - Background luminance
By increasing the luminance of the background walls and ceiling, effective glare can be reduced. Some luminaire designs incorporate uplighting to take advantage of this effect.
Workplace lighting and glare
Keeping staff comfortable, productive, and safe is essential in any workplace, which makes intelligent lighting design—particularly glare reduction—a key consideration. Beyond the use of low-glare light fittings, designers can employ strategies such as indirect lighting, wall washing, and careful use of surfaces, textures, and colours.
Modern LED lighting technology is another valuable tool, with advanced control systems like DALI enabling designers to tailor lighting to a space and to individual needs by adjusting luminaire strength and tone in selected rooms and even for specific light fittings.
New sensor systems can automatically regulate luminaire output based on natural light levels, improving both occupant comfort and energy efficiency.
Explore our range
Explore the full range of Ektor LED lighting and emergency exits.
Share the article
Resources
Check out more information about Ektor’s quality components.
