Interior Lighting Design Should Make Light Serve People's Health And Well-being

- May 24, 2019-

People have been trying to improve their health.We Chinese always believe that "food is better than medicine" and "life depends on exercise", so we have formed a set of mature theories and experience in the aspect of medicinal diet and fitness.Even when we need to use drugs to treat pain, both traditional Chinese medicine and western medicine can meet our needs to some extent.


Among other things, we haven't overlooked the positive effects of light on our health, such as the well-known physical and mental health benefits of proper exposure to the sun.However, we have been greatly ignored the impact of indoor lighting on our physical and mental health.In modern life, the vast majority of people spend about 90% or more of their time indoors every day, and many indoor Spaces are even deprived of sunlight for a long time.If we still pursue everyday only so brief bask time, and do not make full use of to be in indoor so the illumination that period of time will accept health, be a bit too much for one's own sake?


So the question is, since light can affect our health, how can we use it to make us healthier?This requires us to think outside the box about how light positively affects our comfort and well-being.So what is our conventional wisdom?"Lighting is to make the room bright", "the light can not be too bright, otherwise dazzling uncomfortable", "the light can not always flash, otherwise people uncomfortable"...Admittedly, these are our traditional thinking about interior lighting, but these are the most basic requirements.


First, we need lighting that makes us feel comfortable and pleasant.


Just as we need delicious food to satisfy our appetite, we also need "visible" lighting to please our vision.Many successful lighting designs are not actually based on the improvement of people's physical health needs, but from the most basic sense of comfort of the whole space, skilled use of color and spatial aesthetic skills, let people feel very comfortable in a space.


Softness, shadow control, and direction of illumination are subtle lighting effects that are not necessarily functional means but define the lighting space and the objects within it.These effects enhance people's perception of the surrounding buildings through the combination of light and shadow.


Dimming operations can also have a positive effect on mood, including "dimming to zero," "dimming to warm," and the individual dimming of each light fixture.Among them, the operation that dim to warm color is particularly important.The color temperature is usually 3000K or 2700K in high brightness. When the brightness is lowered, the color temperature decreases simultaneously and the light color becomes warmer. In low brightness, the color temperature is usually 2200K or 1800K.This works just as well as mimicking the familiar dimming properties of incandescent bulbs, and it also works well to boost the body's production of melatonin, a natural sleep hormone, at night.The effect of dimming to a warm color can also give people a warm and comfortable feeling at night, which is conducive to people's sleep.


Second, we need to be conducive to the health of the people-oriented lighting.


So-called "humanistic lighting" is actually a great concept, let people feel comfortable lighting is belong to the category of humanistic lighting, but this humanistic lighting points can help keep people on physiological level circadian rhythm lighting concept, the basic way is to indoor illumination simulate real natural features.The effect of humanistic lighting is usually demonstrated by comparing lighting design cases to understand how people's health status and behavior have improved after using humanistic lighting schemes.Experimental study of sleep science has also confirmed the objective and significant effect of human-oriented lighting scheme on improving sleep quality.


The control of the brightness of a single light source and the dazzle of multiple light sources can reduce people's visual discomfort and improve people's acceptance of the lighting design.While there is no specific scientific way to define the factors that contribute to discomfort, some of the indicators proposed by WELL building standards 2 (WELL v2) are expected to become generally acceptable measures:


· the Unified Glare Rating (UGR) value shall meet the following conditions:

O for lamps with installation height of 5 meters or less, UGR 17.

O for lamps with installation height higher than 5 meters, UGR 20.

· shading Angle () if required:

O no shading is required for lamps with brightness less than 20000 CD/m2

O for between 20000 to 50000 CD/m2 brightness of lamps and lanterns, alpha acuity 15 °.

O for between 50000 to 500000 CD/m2 brightness of lamps and lanterns, alpha p 20 °.

O for the lamps and lanterns of brightness is higher than 500000 CD/m2, alpha acuity 30 °.


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  •                                                                                 Diagram of shading Angle.


Case data have proved the positive effect of human-oriented lighting scheme on improving people's mood and physical conditions, but this scheme is still at the level of dynamically adjusting color temperature and illumination. We need more experiments to explore whether the dynamic change of other parameters will have a positive impact on human body.


What other factors need to be considered?


As mentioned before, flicker is very unpleasant and can also cause health hazards, and may even cause casualties in some workplaces.Blinking at frequencies below 100 hz has been clinically documented to be associated with dizziness, eye fatigue, and even epilepsy.Flashes of 100 to 120 Hertz reduce visual sensitivity and affect reading.Flicker frequencies above 2000 hz are not directly visible to the human eye, but it is still possible to observe rapidly moving or rotating objects in this light.When photographing or recording video in flickering light conditions, the lens captures the flicker and produces weird images.In a word, scintillation is the most unpleasant factor in modern lighting, especially in modern indoor lighting.IEEE P1789 standard has detailed introduction, definition and restriction Suggestions on scintillation phenomenon. Title 24 standard in California of the United States has more stringent restrictions on indoor lighting scintillation, which can be referred to by interested readers.


Another factor to consider is the Spectral Power Distribution (Spectral Power Distribution (SPD), often referred to as spectrum), and the influence of spectrum for photopic vision and scotopic vision.Photopic vision refers to the vision of luminance in the range of 10 to 108 CD/m2. Usually, our vision in daytime or bright space belongs to luminance vision.Scotopic vision refers to the vision in the range of 10-3 to 10-6 CD/m2. Usually, our vision in dark night belongs to dark vision.Different spectra have different effects on the light vision and dark vision of human eyes, and this effect will make people have different impressions on different lighting conditions.This effect can be quantified into an indicator called "Scotopic/Photopic Ratio" (S/P Ratio). Generally speaking, the larger this indicator is, the better people's visual perception will be.Tm-12 and tm-24, two technical memos issued by the lighting engineering institute of America (IES), have detailed definitions and application Suggestions for this index to achieve the best visual effect.


In addition, appropriate exposure to sunlight is the most beneficial to health.Article 61 of the current WELL v1 requires that 75% of the work surfaces in the work area should be kept within 7.6m from the sunlit Windows, while 95% of the work surfaces should be kept within 12.5m.Article 62 further requires that at least 55% of the occupied space should have at least 50% of the time per day to maintain illumination above 300 lux, but no more than 10% of the space illumination above 1000 lux in 250 hours throughout the year.These recommendations also call for buildings to be equipped with controlled shading devices to eliminate harsh sunlight from worksurfaces.


conclusion


This paper briefly introduces some elements of interior lighting design, which have important influence on lighting effect.However, it should be noted that they are not isolated elements. On the contrary, many elements are interactive, interdependent and sometimes even contradictory.Interior lighting design is an organic whole, but also an art, especially when the art is introduced into the modern concept of people, its complexity will inevitably increase.This requires modern lighting designers to further understand and learn the physiological function of human body on the basis of mastering the traditional design concept, and have a deeper understanding of the concept of people-oriented lighting, so that the works designed can further serve the well-being of people's physical and mental health on the basis of ensuring artistic beauty.