The Dark-Sky approach: lighting design for people and environment

How a thoughtful design of artificial light at night can minimize light pollution and help us preserve the dark sky

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Highlights

The developments in outdoor lighting of the last century have enabled us to fully live the city by night: we can gather in parks and squares also after sunset and do more night-time outdoor activities; we can walk and drive in the streets safely and have good orientation; cities and their landmarks are enhanced by lighting, creating specific visual experiences and atmospheres, encouraging people to visit them and spend time in the urban space.

Designing for exterior lighting – and urban lighting in particular – always strives to balance different needs: making people feel safe and comfortable in the space at night, allowing good visibility and recognition of other people or obstacles, realizing welcoming atmospheres, minimizing energy consumption and enhancing the identity of the outdoor area. Outdoor lighting has thus slowly broadened its scope: from visual task and visual comfort to visual experiences and therefore to social interaction. During this process, cities and other outdoor spaces have become more and more overlit, leading to increasing light pollution

1. Dubai nightscape

Unmasking light pollution: impacts on health, environment, and economy

Research so far has identified three main elements of light pollution:

Urban sky glow – the phenomena of the reflection of artificial lighting into the sky, manifesting mainly as a glowing dome above cities and towns and preventing us from seeing the night sky. 

Light trespass – the trespass of outdoor lighting into adjacent buildings, disturbing activities or the sleep-cycle of residents.

Glare – the feeling of discomfort arising when luminaires are not properly shielded, shine too brightly or create an excessive contrast in the space. 

In addition to incredible waste of energy and money, these phenomena create serious damage to the health of humans, animals and plants. Humans rely crucially on their circadian rhythm, which is regulated by darkness and light. When people are exposed to light while trying to sleep, their melatonin production is often suppressed, resulting in sleep disorders, fatigue, stress and many possible diseases. Furthermore, it has been estimated that sky glow and light trespass compromise more than 60% of the world’s natural habitats. Rural areas are losing their night time to spill lighting coming from overlit outdoor areas, and as a result, wildlife and their natural habitats are severely affected. 

 
2. Sky glow

Sustainable strategies to reduce light pollution

1. Less is more
First and foremost, lighting designers need to reduce as much as possible the amount of light for outdoor areas. In dark environments we can see obstacles and distinguish the surroundings even with very little light and low uniformity. Of course, it is necessary to guarantee the minimum illuminance levels required by the standards for ensuring safety, but ‘less is more’ remains the basic rule to follow, both in terms of light intensity and in terms of quantity of luminaires. It’s absolutely not necessary to illuminate everything, light should be planned only where it is really needed. 
 
2. Shield the luminaires
All luminaires for outdoor use should illuminate only downwards and be properly shielded to avoid any upwards light emission. Diffuse “globe” fixtures and festoon lights may be aesthetically nice, but the amount of energy they waste and the amount of light they emanate towards the night sky should be reason enough not to use them anymore. Uplighting light fixtures can be used only if they are correctly aimed toward buildings or monuments and emit minimal spill lighting in the surroundings. 

3. CCT matters
Selecting the right color temperature is crucial: blue light can harm both humans and wildlife at night and compromise their sleep-awake cycle. It is necessary to have only warm lighting for outdoor areas, with a maximum CCT of 3000K or using mostly warmer colours when coloured lighting is designed. 
 
4. Lighting controls can make the difference
Timing and light controls are absolutely necessary. The existing technology allows us to control the intensity of the light and the length of its activation, using motion and daylight sensors or astronomical clocks. It is critical to control light as much as possible in order to have it not only where it is needed, but also when it is needed.
 
5. Check the lighting masterplan
Many cities are developing a lighting masterplan to best tackle all the aforementioned topics and find the right balance between the different needs and limitations of exterior lighting. Lighting Masterplans provide useful guidelines of what is it allowed and what must be avoided depending on the context and are the first resource that should be used, if available, when designing for outdoor lighting.  
3. Bollard by Louis Poulsen

International Dark Sky association’s mission

Raising awareness about the growing impact of light pollution is the purpose of the International Dark Sky Association (IDA), which in the 1980’s started the dark sky movement. The IDA aims to reduce light pollution by providing leaderships, tools and resources for individuals and governments and strives to promote responsible outdoor lighting. On the IDA’s website it is possible to find many information, research studies and tips and tricks related to outdoor lighting and how to best preserve the dark sky.  

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