The National Electrical Manufacturers Association (NEMA) published NEMA LS 20001-2021, White Paper on Unified Glare Rating (UGR). This new white paper explains the original intent of UGR, its proper uses, and common misuses.

UGR is one of the few lighting metrics that practitioners use to model and design appropriate lighting to meet application and task visual needs. In the hands of a competent lighting designer, it can provide insight into visual comfort expectations when included as part of a complete lighting design because it incorporates room layout, luminaire layout, the task being performed, and surface reflectances.

However, improper use of the UGR approach can result in poor lighting design, poor luminaire design, and unintended glare. The NEMA white paper aims to prevent such misuse through education on the context of UGR and by demonstrating how erroneous use as a luminaire-specific qualification metric can lead to glare inaccuracies for lighting designs.

The audience for this paper includes lighting designers, luminaire manufacturers, and luminaire specifiers. NEMA LS 20001-2021 is available for download at no cost on the NEMA website.