UGR Value

Lighting is important for people's comfort and well-being. However, it is also important to ensure that lighting is safe and does not cause glare. The Unified Glare Rating (UGR) is a measure that determines the glare caused by artificial light indoors or, for example, in a car.

Scale from 1 to 19

UGR values are expressed on a scale of 1 to 19, with lower values representing less glare and higher values representing more glare. It is therefore important to keep the UGR value in the room as low as possible to avoid glare and associated discomfort. How is the UGR value determined?

How is the value calculated? It is based on several factors, including lighting height and distance, reflections from the room surface and light intensity. There are several ways to determine the UGR value, but the most commonly used method is the 'zonal cavity method'.

Several factors are taken into account, such as:

• Type of light source:

The colour temperature and illuminance of the light source play an important role in determining the UGR value.

• Room dimensions:

Larger rooms need more lighting to provide adequate illumination.

• Ceiling height:

Higher ceilings mean more space for lighting, which affects UGR values. These factors can be used to calculate a UGR value, which indicates whether lighting meets glare criteria.

Which UGR value for in cars?

For vehicle lighting, a value of 19 or lower is recommended. This value is classified as ‘very low’ and guarantees good comfort and safety for the driver and other road users. It is important to note that some countries have specific requirements for the UGR value of vehicle lighting, so it is always best to check the requirements in your region. In our blog on functional LED interior lights, we explore various options for safe interior lighting in more detail.

What is an acceptable value indoors?

In indoor spaces, acceptable values between 19 and 22 are often assumed. It depends on the specific application and the user's expectations. For some applications, such as computer workstations, lower UGR values are recommended.

How can I reduce the UGR value of my lighting?

There are various ways to reduce the UGR value of lighting, such as using luminaires with a controlled luminous flux, using light beams with a narrower beam angle, and increasing the distance between the luminaires and the surfaces in the room. The use of diffuse lighting fittings and the application of lighting control (such as dimming) can also contribute to a lower value.

Table of UGR values and recommended applications:

Please note that the recommended UGR value may depend on several factors, such as: Specific room conditions and user expectations. It is always advisable to refer to specific standards and regulations for specific applications.

If you’re looking for functional LED lighting for inside your vehicle, TRALERT® has an extensive range of LED interior lights that provide safe illumination.