How to reduce UGR?

With?the development of technology?of LED chips, uncomfortable glare becomes serious with the LED luminaires brighter. UGR limits are used as a mandatory standard for luminaires, not just as a reference.

1.What is UGR?

UGR(Unified Glare Rating) is an expression of the relative intensity of the light from a light fitting compared with the intensity of the light from the surrounding area.

Thus, it can only be calculated for an indoor lighting installation?and cannot be calculated for an exterior lighting installation (such as?street lighting)?and it cannot be calculated for a lighting installation on it’s own.

As an objective measure of glare, UGR is used to measure the discomfort caused by glare in indoor lighting environments and is used by lighting designers to help control the risk that occupants of a building will experience glare from artificial lighting.

UGR values range from 40 (extremely high glare) to 5 (very low glare). In most situations, the less glare the better.?But it cannot be eliminated in total.

2. Classification of glare and its hazards

Classification:

• According to the way glare is produced, glare can be divided into direct glare and indirect glare. Direct glare: Produced by luminous objects present in the field of view, especially near the line of sight.Indirect glare: Even though the light source itself will not be visible to the observer, objects with high reflectivity or gloss will act as an indirect light source to produce glare after being illuminated by the light source. Indirect glare can be further classified into reflected glare and light curtain reflections.
• According to visul status, glare can be divided into incapacitating glare and uncomfortable glare. Incapacitating glare: Loss of certain visual functions of the human eye, instantly reducing the ability of the human eye to detect objects. Uncomfortable glare: Only caused subjective discomfort, but has not affected the visual function yet.

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Hazards:

Prolonged glare can cause psychological discomfort and visual fatigue, which in turn can lead to irritability, poor concentration, migraines, eye diseases, and other physiological discomforts.

Therefore, international standards such as EN12464 recommend maximum UGRs for different situations. UGR<19 is recommended for many office and classroom settings.

3. How to calculate UGR?

UGR is calculated in widely used lighting design programs such as Relux, Dialux, and AGi32.

From section 1, we know the UGR cannot be used to calculate lighting fixtures alone, but in comparison to the surrounding area.

The data required to be input include the photometric files of the fittings to be used in the lighting scheme, the room geometry, the surface reflectances and the number and spacing of the fittings. From these data, the lighting design software will calculate the UGR.

Here is the formula for calculating UGR, which is not as complicated as it looks.?Follow the notes and you will have a much clearer understanding of this important measure of the quality of a lighting installation.

4. How to reduce UGR?

As we know in previous section, UGR?can be reduced only, not eliminated.

It's measured for an installation, not for a light fitting. Nevertheless, the design of a light fitting can have a significant impact on the UGR of the installation where it is used.

So we can deal with it from the design process and the installation method.

Design Process

Typically, a luminaire is comprised of shell, lighting sources, a power supplier, PCB, lenses, or glass, and there are many means to control the UGR value during the initial design period.?

• Deep-seated anti-glare technology With high-quality reflector shape and curvature, with low gloss material as the surface decoration, you can achieve the purpose of anti-glare. Most of these products are called deep anti-glare lamps and lanterns, of which hotel ceiling spotlights are the most representative.

• Frosted or matte the light optics Diffuse the light from the concentrated bright spot of the luminaire to reduce the surface brightness value that the human eye can see, and the light looks softer, to achieve the purpose of controlling glare.

• Honeycomb the lens surface Adopting bionic technology, a lot of small masks like honeycomb structures are formed on the surface of the lamp mask. When the light source enters the eyes, the small masks of the honeycomb structure reflect the strong light and the stray and scattered light on the surface of the object, so that the light becomes parallel light and concentric light, avoiding the stimulation of the strong light, to achieve the effect of protecting the eyes.

• Concave penetration divergenceConcave lenses have a diffusing effect on light. Making the lampshade of the lamps and lanterns curved makes the strong light from the lamp beads softer, and also diffuses the light to achieve a wider range of illumination and more uniform light.

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Installation method

In addition to the design process, UGR glare is actually related to the installation location and method of the luminaires. Even for general non-glare luminaires, as long as the installation height and location are rational, the glare will be greatly reduced.

According to the previous formula and the annotation, we can reduce the UGR value according to increasing the?Lb value, or lowering the Ll^2 value, like adding more background luminance, suspended fitting with some uplight, and lower luminous intensity each luminaire.

When lower the ωl value and increase the Guth Position Index, angular distance enlarges, which means the light source deviates from the line of sight, causing small plane illumination in the human eyes, such as?positioning the luminaire a greater distance further from the viewer and reduce the light enter human eyes directly.