SLS | UGR

Unified Glare Rating (UGR) is a measure used to evaluate the discomfort caused by glare from luminaires (lighting fixtures) in indoor environments. It is particularly important in workplaces and other areas where visual comfort is crucial for productivity and well-being. It must not exceed 3000 candela per square metre (cd/m2)*, if you want to create a pleasant experience in the office. The UGR method takes into account the luminance of walls and ceilings as well as all luminaires that contribute to the sensation of glare.

Standards

UGR is standardized by organizations such as the International Commission on Illumination (CIE). These standards provide guidelines on how to measure and calculate UGR, ensuring consistency in assessing and improving visual comfort in various settings.

Purpose

UGR aims to quantify the discomfort glare perceived by an average observer in a given space. Discomfort glare can reduce visibility and cause visual fatigue, impacting overall comfort and efficiency.

Calculation

UGR is calculated based on factors such as the luminance of the luminaires, their position relative to the observer, and the room's dimensions and surface reflectances. These factors help determine how likely it is for an observer to be bothered by glare.

Application

Architects, lighting designers, and engineers use UGR to select appropriate lighting solutions for different spaces. By choosing luminaires with lower UGR ratings, they can minimize glare and create more comfortable and productive environments for occupants.

Scale

UGR values typically range from 10 to 30. Lower UGR values indicate less glare and better visual comfort. For example, UGR below 19 is considered suitable for most office work, while values above 25 may cause discomfort.

To comply with the WELL L04 Electric Light Glare Control requirement, each luminaire must maintain a UGR of 16 or less in all spaces except industrial areas, where a UGR of 19 or less is required.