What is UGR, or the Unified Glare Rating? Here we explain all the concepts you need to know.
UGR, or Unified Glare Rating, is a key concept in LED lighting, essential for ensuring a comfortable and efficient environment. In this article, we explain what UGR is, how it affects indoor lighting, and how you can optimize it.
What is glare?
Glare is an uncomfortable visual sensation that occurs when an intense light source, such as a light bulb or sunlight reflected on water, enters our field of vision. This phenomenon can be classified into two types: disability glare and discomfort glare.
- Disability glare: Creates a luminous veil that reduces the clarity and contrast of what we see, making vision blurry. A typical example is when a car with high beams dazzles us while we are driving at night.
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Discomfort glare: Occurs when the light is so intense that it causes eye strain, mainly affecting indoor spaces. UGR is based on this type of glare.
What does UGR measure?
UGR (Unified Glare Rating), developed by the International Commission on Illumination (CIE) in 1995, measures the perceived level of glare based on the observer's position and viewing direction in indoor environments.
The UNE-EN 12464-1 standard establishes the permissible UGR limits according to the type of activity. The higher the UGR, the greater the sensation of glare, indicating lower lighting quality.
UGR values range from 10 to 31, with 16 considered non-glare and 28 considered glaring. The most common values in practical applications are 16, 19, 22, 25, and 28, with increments of three units because smaller changes are not perceptible to the naked eye.
What is visual comfort?
According to studies, the human eye perceives illuminance levels between 3 and 100,000 lux. And to perform an activity comfortably, it requires between 100 and 1,000 lux.
Visual comfort is defined as the pleasant visual sensation perceived by people while performing an activity. This promotes concentration, creativity, and intensity, among other factors, without causing discomfort.
We consider that there is no visual comfort when there is excessive light, direct lighting, flicker from the luminaire, low CRI levels, or exaggerated contrasts.
How do we identify environments with high UGR?
Glare mainly occurs due to excessive light or direct exposure to a light source, either through the luminaire itself or through reflections on surfaces such as windows or screens.
These environments not only cause visual discomfort and headaches, but also significantly reduce concentration and performance at work or while studying.
The main variables that affect the UGR value are:
- The technical and structural characteristics of the luminaire.
- The reflectance of adjacent surfaces, such as screens, windows, surfaces and shiny tables, mirrors, etc.
- The observer's position relative to the luminaire, that is, the direct lighting angle produced by the lamp's height and distance.
How can we reduce the UGR level and improve visual comfort?
There are currently many products specifically designed with low UGR levels, or low Unified Glare Ratings.
These range from LED panels with opal covers to lamps and luminaires specifically developed to prevent glare without sacrificing lighting performance.
