UGR and glare in sports lighting: the guide

A lighting installation can show the right lux level and still be uncomfortable, even dangerous, if the sources dazzle. The UGR index (Unified Glare Rating) measures precisely this risk of discomfort glare. This article explains what UGR is, how its scale is read, which thresholds to aim for depending on the use · from the sports ground to the office · and through which practical levers to control it from the design stage.

What is glare, and why measure it?

Glare occurs when a light source that is too bright in the field of view degrades perception. A distinction is made between disability glare (which reduces vision) and discomfort glare (which tires and disturbs without preventing sight). In indoor lighting, it is mainly the second that one seeks to control. In sport, the issue is twofold: a player who looks up at the ceiling must not be dazzled at the moment of a shot or a catch; in the office, glare harms comfort and concentration on screen.

The UGR index: definition and scale

UGR is a standardised method (associated with the EN 12464-1 standard for indoor workplaces) that quantifies the discomfort glare produced by the luminaires of an installation, taking into account their luminance, their position in the field of view and the luminance of the background. It is an index: the lower it is, the higher the comfort.

The scale generally ranges from about 10 (no perceptible glare) to 30 (unacceptable discomfort glare), graduated in steps of 3, a value corresponding to the smallest perceptible difference in glare: 13, 16, 19, 22, 25, 28. Thresholds are thus expressed as "UGR ≤ 19".

Remember: a low UGR is not incompatible with high illuminance. It is perfectly possible to have a lot of lux and excellent visual comfort · that is the whole purpose of careful design.

Which UGR thresholds to aim for by use?

The EN 12464-1 standard sets UGR limit values according to the activity. Some commonly used benchmarks:

Precision work: UGR ≤ 16.
Offices, meeting rooms: UGR ≤ 19.
Industrial premises: UGR ≤ 22.
Circulation areas, corridors: UGR ≤ 25.

For commercial workspaces, the reference threshold is therefore UGR ≤ 19: it is a central criterion of visual comfort, particularly in offices and meeting rooms, where people work for long periods under artificial lighting and on screens.

The special case of sports grounds

Sport adds a difficulty: the direction of gaze is very variable and often directed upwards. The reference frameworks specific to sports halls govern glare through their own methods and thresholds, which can differ from the UGR approach used in commercial buildings. The issue remains the same: preventing a luminaire from becoming a direct source of discomfort at the moment the player most needs to see the ball.

In practice, in a gymnasium or on an indoor court, several precautions are combined: placing luminaires outside critical lines of sight, sufficient height, louvred optics and good overall uniformity. These principles apply to all indoor sports · see our dedicated guides, for example lighting a basketball hall to FFBB standards or lighting a football pitch to FFF standards.

Direct glare, indirect glare and veiling luminance

To deal with glare properly, its forms must be distinguished. Direct glare comes from the luminaires themselves, seen directly in the field of view: this is what UGR measures. Indirect glare, or reflected glare, arises from reflections of light on shiny surfaces · a varnished gymnasium floor, a lacquered work surface, a screen. Finally, veiling luminance refers to the loss of contrast caused by stray light. In sport as in the office, good design deals with all three: low-glare optics are chosen, very reflective surfaces in the critical axis are avoided, and the general distribution of light is carefully managed. A lighting installation perfectly sized in lux can thus remain uncomfortable if these phenomena are not anticipated.

Why glare matters as much as illuminance level

Underestimating glare means risking an installation that complies on paper but is unpleasant in use. In the workplace, too high a UGR results in visual fatigue, headaches and reduced concentration on screen tasks · with a real impact on productivity and well-being. In a sports context, glare degrades performance and can be a safety issue, particularly during aerial phases of play where perception of the ball is critical. Controlling glare is therefore not a refinement: it is an integral part of the quality of a lighting installation, just like lux level and uniformity.

The levers for controlling glare

Reducing UGR (or sports glare) relies on a few practical levers, to be used from the design stage:

The optics: closed or louvred optics, or optics with low apparent luminance, limit the direct brightness of the sources in the field of view.
The mounting height: mounting the luminaires higher reduces the angle at which they appear and therefore the perceived glare.
Orientation and positioning: avoid placing a bright source in the direct line of sight of the user (player, operator, person seated at a desk).
Background luminance: a light-coloured ceiling and walls reduce the contrast with the luminaires and lessen the sensation of glare.
The choice of product: a luminaire designed with a low stated UGR makes it easier to reach the target thresholds.

For workspaces, products such as the VERTIGO FRAMELESS panel are designed to offer good visual comfort and controlled UGR, suited to the requirements of commercial buildings.

UGR is validated by the photometric study

UGR depends on the geometry of the room and the position of the observer: it cannot be read from a product sheet alone. A photometric study (in software such as DIALux) calculates the actual UGR for the relevant positions and directions of view, in addition to the lux level and uniformity U0. It is the only way to guarantee, before purchase, that the installation will respect the target comfort thresholds. We explain this approach in our article: why carry out a photometric study before purchase.

It should also be remembered that a UGR value stated on a product sheet is calculated for a reference configuration (room dimensions, height, standard reflectances). It gives a useful indication for comparing luminaires, but does not predict the result in your actual space: the same product can show a different UGR depending on the installation height, the spacing between light points or the colour of the walls. That is why verification by simulation remains essential on projects that are demanding in visual comfort, whether an office floor, a meeting room or an indoor sports facility.

FAQ

What does the UGR index mean?

UGR (Unified Glare Rating) is a standardised index that quantifies the discomfort glare produced by the luminaires of an indoor installation. The lower the value, the better the visual comfort. The scale generally ranges from about 10 to 30, in steps of 3.

What UGR should be aimed for in an office?

For offices and meeting rooms, the EN 12464-1 standard sets a reference threshold of UGR ≤ 19. Precision work requires UGR ≤ 16, while circulation areas tolerate up to UGR ≤ 25.

Does UGR apply to sports halls?

Sports halls often fall under specific reference frameworks and methods for assessing glare, which can differ from the UGR approach used in commercial buildings. The objective remains the same: preventing a bright source in the field of view from disturbing the athletes.

How can the glare of an existing installation be reduced?

Action can be taken on the optics (louvred sources), the height and orientation of the luminaires, the luminance of the walls and ceilings, and the choice of low-UGR products. A photometric study makes it possible to check the effect of these choices before works.

Need a photometric study?

The audit and the photometric study are the work of a lighting design office: we recommend the expertise of the Luminance Consulting agency, the lighting design office that contributes to developing our ranges of luminaires based on an in-depth analysis of the needs of the most demanding customers. Luminance carries out the audit of your installation, the DIALux study and the compliance check. Rexylum, for its part, designs and supplies the prescribed luminaires and lighting solutions: for the choice of equipment, contact us.