Glare and its standardised method of measurement, UGR (Uni ed Glare Rating), is increasingly spoken of these days as the lighting market overcomes its initial infatuation with LEDs and starts to ask the hard questions, especially in relation to overall light quality. So why is glare important? In broad terms, uncontrolled glare increases the risk of errors, fatigue and consequently accidents. Glare is generally categorised as either disability or discomfort glare. Although not as drastic as the blinding effects associated with disability glare, discomfort glare can take its toll if we are spending extended periods under lighting with poor glare control.
Discomfort glare is broken down into either direct or reflected categories. EN 12464-1:2011 is the CE standard relating to workplace lighting, focusing on two interrelated components associated with glare – UGR and Luminance at 65° of <3000 cd/m2. Other relevant documentation includes SLL and CIBSE Code for Lighting.
Recommended limits for glare have been set in EN 12464-1 for a variety of workplace categories, including:
- UGR<16 – Technical Drawing Office.
- UGR<19 – Offices, Schools.
- UGR<22 – Workshops, Receptions, Retail.
At this point in time, LEDs are the brightest light sources utilised in general lighting with the most light emitted per unit area. With the ongoing miniaturisation trend in the LED market, LED package sizes have reduced, while relative light output has increased, resulting in further gains in brightness and thereby leading to greater propensity for glare.
Meeting glare requirements is a delicate balancing act – this is where good lighting designers come into their own by using the relevant light fitting photometric files with specialist light modelling software to produce designs where the competing requirements of UGR and uniformity tensors are met as per the specification.
LED Group is particularly discerning in delivering its ROBUS UGR<19 LED panel ranges, although there is evidence that not all major lighting companies are choosing this responsible approach. For example, it is completely misleading to market and promote an LED panel as UGR<19, where it can be proven by analysing the photometric files in a lighting design that the panel achieves UGR<19 only for a maximum room size of 3.2m x 6.4m. Although not a legal requirement, compliance with EN 12464-1 is recommended as best practice.
There is a real need for clarity and openness on glare requirements in the lighting market and at the very least, customers deserve to know and understand if a light fitting rated as UGR<19 does not perform as described. In the meantime, the onus is on specifiers to look beyond claims and carry out due diligence by engaging fully with lighting companies and lighting designers in order to select products that meet the glare requirements of the project.
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