Why should we be concerned about glare?

Glare is a visual sensation caused by excessive and uncontrolled brightness and can have a detrimental effect on our wellbeing. Nigel Box, Technical Director at Sylvania Lighting Europe, talks us through the impact glare can have in our working environment.

Wellbeing within the office is vitally important to keep employees comfortable as well as ensuring they can be as productive as possible. Office work can be particularly demanding on the eyes, especially when employees are required to stare at screens all day, whether they are in office spaces or working from home remotely. Lighting can play a huge role in creating the right ambience within a space and, in some cases, if not done correctly can cause a number of health issues.

Glare is a visual sensation caused by excessive and uncontrolled brightness and it can range from being simply uncomfortable right through to completely disabling. It is subjective, and sensitivity to glare can vary widely.

There are two commonly considered types of glare:

Discomfort Glare – this is the sensation of annoyance or even pain induced by overly bright sources, but it will not actually stopping you seeing. Discomfort glare can be caused by direct or reflected glare and can be a result of simple bright sunlight. It can impact individuals in different ways and will have varying degrees of intensity, however, even in milder cases it can cause visual discomfort such as eyestrain and fatigue. For those that suffer from a sensitivity to light, glare can occur at any time of day.

Disability Glare – is the reduction in visibility caused by intense light sources in the field of view and can cause a loss of visibility from stray light being scattered within the eye. As the name suggests, disability glare is far more detrimental than discomfort glare and the high level of light produces a glare that can actually interfere with or block vision. It can be, for example, a result of bright sunlight shone directly into the face or bright lights from an oncoming vehicle.

Both glares simultaneously influence as the eyes try to auto correct the issue. This can cause loss of concentration, more frequent mistakes, and fatigue. So, what can we do when designing lighting schemes to counter the effects of glare?

Unified Glare Rating (UGR)

The glare of all luminaires that are in the room regularly can be evaluated with the UGR method, as specified in the standard EN 12464-1 “Lighting of indoor workplaces”. Part 1 of BS EN 12464 specifies requirements for lighting in main offices areas and the associated areas in terms of quantity and quality of lighting. In addition, recommendations are given for good lighting practice including studying glare and shielding against it, colour aspects and appearance, colour rendering, maintenance and energy efficiency requirements.

UGR is calculated using a precise formula. Essentially, this formula measures the luminance of a luminaire divided by the background of visible luminance from the room. The UGR ranges from 5 to 40. The lower the number, the better. For example, a low UGR of 10 means the glare is so discreet it will go unnoticed, while a UGR of 30 will definitely cause distraction.

UGR is applicable to lighting installations, not luminaires. The formula requires the prior knowledge of the position and brightness of each potential glare source. It is quite accurate, but relatively difficult to work with. It is best calculated with computer software.

Glare calculations are complex and involve summing all the light from all sources at a particular angle entering the eye at a particular location. Strictly speaking, there is no such thing as a ‘UGR19-compliant’ luminaire. There are luminaires whose performance supports a UGR-compliant design or installation, but compliance can only be determined once the ergonomics and geometry relative to the occupants of a space have been assessed. If a manufacturer claims UGR19 compliance, then it can only be for a set of pre-determined conditions. Thus, a luminaire UGR is a simplification which enables us to determine if it is likely to cause discomfort in specific types of work or office environment.

Tabular Method

This is a procedure which is followed in order to determine the UGR value of a lighting installation in a standard room. The lighting designer should bear in mind that the ‘standard room’ rarely represents real world situations. In this method, the floor has a standardised reflectance of 20%, walls: 30% to 50% and ceiling up to 70%. White walls or ceilings with a higher reflectance (75 to 90%), such as frequently occur in indoor spaces, are not taken into consideration in this approach. The observer is positioned either across or along the luminaire axis. It does not permit an angle of vision diagonal to the luminaire axis. Also, it is based exclusively on rectangular room geometries. It must be applied for each individual type of luminaire, if more than one luminaire type is present in the room.

Sylvania offers a number of solutions that are ideal for office environments including the new Optix Linear luminaire. With its high-performance glare-controlled optics with optimised diffusers and reflectors, Optix Linear is perfect for a wide range of applications such as office, education, data centres and other circulation areas. Optix Linear can be mounted individually or in continuous runs with seamless light effect providing greater flexibility over the design of the lighting scheme. It is available in Warm White (3000K), Neutral White (4000K) and Tuneable White (3000K – 6000K) colour temperatures. Optix Linear meets and exceeds UGR <16, with aluminised optics plus the implementation of CRI 90 for increased visual comfort, meeting the required standards and making it ideal for office environments

We have learnt how to work in different environments over recent months and when we go into the office it will feel different to how it was previously. Ensuring we can still be productive and comfortable in our office environment will still remain a top priority and, as we’ve seen, lighting can play a key role in making sure our wellbeing is enhanced. Glare is an important issue and something that needs to be considered carefully when lighting a space.