Good light is the right light at the right time, tailored to our activities and our personal needs, every day of our lives.

Good light is natural light or electric lighting indoors that mimics the beneficial properties of natural light as much as possible.

The wrong light at the wrong time can lead to problems such as mood disorders, sleep problems, problems with studying and memory, short-term vision problems and long-term health problems.

Scientific research shows that Good Light provides your daily dose of Good Energy.

Being outside during the day is very important for us as humans. After all, the light intensity outside during the day is always higher than inside, by a factor of somewhere between 10 and 500. Sunshine includes infrared light (IR) which warms us and also Ultraviolet light (UV) which, when it reaches the skin, supports the production of vitamin D, important for calcium absorption for healthy bone structure and for the immune system.

The high light intensity we get outdoors during the day is also important for our well-being, our mood, our performance, how we sleep at night and for reducing our sensitivity to light at night. Exposure to high-intensity, full-spectrum daylight ensures that our biological clock is synchronised with the natural 24-hour light-dark cycle. It prevents our body from running late, sleeping fragmented and waking up frequently at night.

So for your Good Energy, the basic advice is simple: make the most of the daylight by being outside during the day. Because we obviously cannot be outside all day, it is best to take the following recommendations into account:

• Unless you want to fall asleep and wake up later, take steps to get at least 30 minutes of natural daylight in the morning immediately after waking up, for example by going for a walk or a bike ride outside, or by walking or cycling to work or school. If it is dark when you wake up, try to 'see' the first half hour of natural daylight after sunrise.
• Take a walk in daylight for at least 30 minutes during your lunch break.
• Play or move around outside during the day.
• Especially for children, it is recommended to spend at least two hours every day outside in daylight.
• Studies recommend that on sunny and/or hot days, you should protect your skin and eyes appropriately from an overdose of UV radiation from the sun for periods of more than 20-30 minutes. The most common ways to do this are by wearing protective cloths, putting on a cap, wearing sunglasses, using sunscreen and/or simply moving to the shade. Wearing a cap reduces the light coming into your eyes by ~50%, wearing sunglasses reduces the light coming into your eyes by 5-95%, depending on the type of glasses.
• If it is not possible to spend time outside, the best alternative is to spend as much time as possible during the day close to (<1m) a window and look outside.

For thousands of years, people have worked and lived outdoors in natural daylight. This has changed considerably since the industrial revolution. Nowadays, people spend 90% of their time indoors. Good light indoors is therefore essential for our health and well-being.

As in nature, indoor light must be attractive, comfortable and of high quality.

This is achieved when interior lighting displays colours naturally, does not cause excessive glare, does not have any unwanted artefacts or flickering, provides an attractive contrast, illuminates the room comfortably, does not make any noise and feels safe.

Here are a few tips to make light attractive inside:

• Let in as much daylight as possible through windows or domes
• Increase the overall brightness of the room. Illuminate not only the work surface, but also the surroundings, e.g. the walls and ceiling.
• Use accent lighting to create an attractive contrast.
• When you purchase lighting, pay attention to the CRI value of the light source. The CRI value stands for Colour Rendering Index and is the degree to which artificial light can faithfully reproduce colours, so that they appear natural. Go for at least CRI 80, but preferably higher.
• Avoid annoying glare. Design for a Unified Glare Rating (UGR) of 19 or less in long-stay zones (≥30 min) and for a UGR ≤ 22 in short-stay zones (<30 min).
• Avoid Temporal Light Artifacts: Flicker Pst ≤1.0 and Stroboscopic Effects: Stroboscopic Visibility Measurement (SVM) ≤1.0. Temporal Light Artifacts create an invisible flicker of light and can cause headaches, eye pain, fatigue or even migraines.
• Limit the audible noise of the lighting installation to ≤24 dBA at 1 m distance.

The amount of daylight we are exposed to outside varies throughout the day, both because daylight itself is constantly changing and because we move around, change what we look at and see, and make changes to the space we are in, such as sitting in the shade.

It might be useful to mimic these changes indoors to some extent. Today, this is possible with the help of LED technology. People need a lot of light during the day and little light at night before going to bed. Good indoor light is stimulating during the day with an intensity that preferably exceeds the traditional standards for indoor lighting by a factor of 5, while in the evening the light level is preferably dimmed by a factor of 5, provided that it remains comfortable and safe.

For people aged 45-50 and above, higher light intensities and probably spectral changes may be required to meet visual and non-visual (biological and emotional) needs. This is largely due to the normal degradation processes taking place in the eye. Many people recognise this as the time when they need reading glasses.

Here are a few tips on how to make light dynamic indoors:

• Use a lighting system that allows you to change the light level; dimming = reducing the light level and/or boosting = increasing the light level.
• Use lighting systems that allow you to change the distribution of light in the room over the course of the day, effectively mimicking daylight.
• Provide horizontal and vertical light levels that ensure adequate visual performance and comfort while providing non-visual (biological and emotional) benefits.
• The following table shows our recommendations for horizontal light levels. These levels are based on a combination of practical experience and scientific arguments. Please note that these light levels must remain comfortable and adequate for the age of the user and the specific task. The timing should be adjusted to personal needs.

As in nature, the spectral characteristics (colours) of ideal indoor light vary depending on the time of day.

The light spectrum can be optimised to suit personal needs and preferences and to support specific tasks.

During the day, the light spectrum must contain a reasonable proportion of short wavelengths (cyan light colour) to provide the revitalising benefits of light.

In the evening and at night, the amount of short wavelengths should be kept to a minimum to promote sleep, allow a good night's rest and avoid disturbance of the day-night rhythm.

With age, from 45-50 years, the spectral characteristics required for optimal functioning may change due to changes in the eye, for example in the development of cataracts.

Here are a few tips for optimising indoor light:

• Use lighting systems that are "tuned" or "tunable" to support a specific activity. A lighting system is tunable if the spectrum is selected to support a specific activity at a specific time of day. A lighting system is considered "tunable" if the light spectrum can be changed. Tunable white systems are the most common and can vary in correlated colour temperature (CCT). Please note that CCT is only an approximation of the spectral content: two light sources with the same CCT can have totally different spectra and therefore a totally different effect on the human non-visual system. The actual spectrum is more important than a CCT number. For this reason, you can also opt for a more sophisticated "tunable" colour system. These systems vary not only in CCT, but also in spectral content and colour.
• Although it is not yet very common, some have reported that it may be useful to use a lighting system with additional spectral benefits found in the non-visual part of the spectrum, e.g. support of vitamin D production or photobiomodulation.
• Design not only for horizontal light levels as suggested by most lighting application standards, but also for light on the eye. During most daytime activities this is the vertical light level at sitting or standing height. These vertical light levels are expressed in MEDI.
• The recommended levels in the table below are partly based on recent recommendations by a group of scientists and age corrections, and partly on our own interpretation of them.

Good Indoor Light can be adjusted to personal needs by the user based on suggestions from the system.

As an individual, you may have a personal preference regarding intensity and a preference for warm or cool shades of (white) light.

In addition, individuals may differ in the timing of their sleep-wake phase, also referred to as a different chronotype. Early chronotypes have a morning preference and late chronotypes have an evening preference.

This results in individual needs regarding the timing of the dynamic 24-hour pattern of light, and both its intensity and spectral characteristics. Furthermore, personal control over the dynamics and spectral characteristics of light is highly valued by individuals.

Here are a few tips to make light personal:

• Consider using a lighting system with a pre-programmed pattern throughout the day that provides the right light intensity and spectrum at the right time.
• Consider using a lighting system with pre-programmed, task-specific light settings to support a range of different activities.
• Many individual users appreciate having personal control over the dynamics and spectral characteristics of the light. The degree of control, or adjustment ranges, can be chosen by the system and made dependent on the time of day.
• Consider the use of more advanced lighting systems that incorporate environmental sensors used to measure and control lighting. The integration of sensors such as temperature, sound detection and air quality can serve to protect and support the health and well-being of occupants. These types of indoor environmental sensors must be connected to other building automation systems.