Visual Performance
Visual performance depends on the quality of illuminance and luminance in the task area and the contrast with the surrounding environment. Although the level of illuminance is a quantifiable element, several parameters must be taken into account in order to achieve the desired result, such as:
- what kind of tasks the users have
- for what period of time the respective activity is carried out
- the age of the users
- the level of the detail
- colours and textures of that space, etc.
Visual Confort
Visual comfort is provided by:
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Colour Rendering Index (CRI).
This parameter has values between 1 and 100. The higher the value, the better the colour rendering. Usually, in the case of lighting projects for offices, any CRI value exceeding 80 is considered acceptable.
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Unified Glare Rating (UGR).
The sensation of glare can be created by lighting fixtures through direct vision of the light source, reflections or very high luminances. An increased UGR creates glare, which is uncomfortable and can lead to vision problems. To avoid glare, consider the background light, the luminance of the lighting fixture, the position of the light and the observer.
Solution
Usually, in the case of office lighting projects, it is recommended to place several lighting fixtures with a significant light surface (for example, ceiling lights) and not very high light intensity. Another option would be lighting fixtures with anti-glare systems such as spilling, honeycomb, and louvre. These lighting fixtures are often found with the attributes “glare-free” or with a “UGR<19/<16/etc”.
Another important aspect is the reflection index of the surrounding materials, so the walls, floor and furniture are recommended to be matte.
Indirect glare ( reflections on the screen, high luminance on the desk, dark background)
Direct glare ( seeing the high luminance of the light sources)
3. Correlated Colour Temperature (CCT).
Colour temperature influences the circadian rhythm (biorhythm) and direct productivity. A warm light induces relaxation, while a cold light helps concentration, attention, and alertness but produces long-term fatigue. One explanation for these phenomena is that cold light has a blue component that allows the body to produce cortisol. It is also called the “stress hormone” and puts us in a state of continuous alertness, causing fatigue and health problems in the long term.
Solution
- That’s why two options for approaching office lighting are recommended. The first would be the one where spaces are treated according to needs. For example, a colder light with values between 6000-6500K can be used for a brainstorming room to increase concentration. However, it is assumed that the time spent in such a room is not long. And for the dining room, a warm temperature of 3000K is recommended to help the relaxation process.
- The second option would be to equip the lighting devices with tunable white, programmed according to the circadian rhythm. Since ancient times, the human body functions according to the blue and reddish wavelengths of natural light. Thus, in the morning, the blue wavelength is significantly increased, stimulating the production of cortisol in the body, preparing the body for any situation, and at sunset, the reddish component contributes to the production of melatonin, which prepares us for sleep. Thus, cortisol and melatonin are hormones that influence the biorhythm, and their dysregulation can cause problems for the body.
Although visual comfort is considered a subjective parameter, there are standards and recommendations of the CRI and the UGR depending on the activities carried out.
4. Flickering.
This term, often used in English, represents the flicker of light. Although sometimes this phenomenon is not visible to the human eye (but through the camera), it causes eye fatigue.
The Visual Environment
The visual environment is the overall mood that is conveyed in a room. Compliance with standards does not guarantee a more pleasant visual environment, so for such projects, the lighting designer works with architects and interior designers to create a welcoming space consistent with the company’s identity.
It is advisable to find a balance between the luminances on different surfaces in the office. By definition, luminance is the ratio between the light intensity of a light source and the projection of the source area on a plane. In other words, luminance represents how the human eye perceives light on different surfaces (for example, an illuminance equal to 500 lx will be perceived differently on a white, glossy surface versus a matte black one). This is measured in candles per square meter.
The Role of Contrast in Office Lighting
A very high contrast can cause visual stress caused by the constant adaptation of the eyes, while a similar luminance throughout the room can create monotony. Since the user’s visual field is usually wider than the surface on which the activity is carried out (e.g., laptop, book, etc.), the surrounding luminances can affect visual acuity, contrast sensitivity and perception speed. A 3/1 contract between the task area and adjacent surface and 10/1 between the task area and background is recommended in office lighting projects.
As for how to accomplish the above, there is no standard solution. The solution mainly depends on the office architecture and interior design. It is suggested to use direct light for the task area and indirect light for the environment to avoid the “cave” effect (dark ceiling and walls – reduce the perception of the space size).
Low contrast, but present. Illuminations of different levels on work surfaces, passageways, ceilings, and walls.
The strong contrast in the office environment causes visual stress through the continuous adaptation of the eyes.
Compliance with Standards
In Europe, there is the standard EN 12464 “Lighting of workplaces” regarding:
- cylindrical illumination – measures the amount of incident light on a curved surface (e.g. a person’s face). The standard recommends a minimum value of 50 lx and a minimum uniformity of 0.1.ț
- uniformity
- the definition of “background area”
- calculation grids
- light distribution
- UGR
- CRI
- CCT
- flickering
- the contribution of natural light. For example, LEED green building certification requires that a minimum of 75% of the space be illuminated by natural light during the day.
Cylindrical Illuminance
LED Lighting Fixtures
It is recommended to use LED lighting fixtures for efficient and eco-friendly lighting. Also, using them alongside presence sensors and sensors that quantify natural light can bring serious energy savings. Since LEDs have a long life, maintenance costs are significantly reduced.
Visioluce can help you both with a wide range of products but also with consulting and designing the lighting design. Our recommendations include the following:
1. Large Luminaires for General Lighting
- Diffuse, uniform light
- Adaptable for coffered ceilings
- The translucent diffuser prevents the feeling of glare
2.Up&Down Lighting Fixtures
- Equipped with a louvre-type anti-glare system, they have a UGR<19
- Provides both direct task light on the work surface and indirect light on the ceiling to avoid contrast with the environment
3. Track lighting systems
- It stands out for its flexibility
- They can include fixtures equipped with wall washer optics for vertical wall lighting
