UGR<19 in Lighting Design: Explanation and Standards
1. Definition and Purpose of UGR
UGR (Unified Glare Rating) is an internationally recognized metric developed by the International Commission on Illumination (CIE) to quantify discomfort glare in indoor lighting environments. It evaluates how likely a lighting setup causes visual discomfort due to excessive brightness or poor positioning of light sources.
2. UGR<19: Standards and Comfort Level
A UGR value below 19 indicates a moderate level of glare that is generally acceptable for most indoor environments.
According to CIE guidelines:
16 < UGR < 19: Represents the threshold between “comfortable” and “uncomfortable” glare. This range is widely adopted for spaces requiring visual tasks, such as offices, schools, and hospitals.
UGR < 19: Ensures that 65% or more of occupants experience minimal or no glare interference, making it suitable for professional and educational settings.
3. Application Scenarios
UGR<19 is typically recommended for:
Office spaces (e.g., workstations, meeting rooms).
Educational facilities (e.g., classrooms, libraries).
Healthcare environments (e.g., hospitals, clinics).
4. Key Considerations
Calculation Basis: UGR is determined by the luminance of light sources, their arrangement, background brightness, and observer position. It cannot be derived solely from a luminaire’s specifications.
Misconceptions Clarified: UGR is not a property of the luminaire itself but a result of the interaction between the lighting system and the environment.
Reducing UGR: Techniques include deep-recessed light sources, frosted diffusers, anti-glare honeycomb grids, and matte finishes to diffuse concentrated brightness.
Note: UGR calculations are not applicable to luminaires with ≥65% indirect light output or narrow-beam asymmetric lighting.
