SPECIAL FEATURE
EXTERIOR LIGHTING
REDUCING LIGHT POLLUTION FOR DARK SKIES As light pollution increases, curbing the environmental impact of urban lighting is growing in importance. In this article, Dan Griffiths, Technical Manager at Tamlite Lighting, outlines how high quality and consistent solutions can make a difference.
N
o one would deny that the problem of light pollution has become more acute as society has moved towards round the clock living. In the words of Amanda Gormley from the International Dark-Sky Association (IDA), “The disappearance of the night sky is tied up in our ever more fast-paced world.”[1] The quality and consistency – or lack thereof – of urban lighting has been a frequent topic of discussion for many years. Simultaneously, there has been a growing awareness of its impact in the environment. Most recently, the Countryside Charity CPRE and the British Astronomical Association’s Commission for Dark Skies sought public assistance in evaluating how light pollution affects the night sky. Such is the current impact of sky glow, it is estimated that 55% of the population in the UK cannot see the Milky Way[2], whilst only 22% of England has pristine night skies, considered as completely free of light pollution. [3] The IDA cites the major causes of light pollution as: “Glare or excessive brightness; sky glow, which drowns out the night sky over urban areas; light trespass or stray lighting falling where it is not needed; and clutter, or confusing groups of bright light sources.”[4] It is not hard to envisage the scale of the problem faced in the UK when you consider that there are more than nine million street lamps and 27 million offices, factories, warehouses and homes. Moreover, the density of urban spaces – and the potential lighting output that comes with it – is increasing at a rapid rate. Data shows that in 1950 the urban population as a percent of the total population was 79%. By 1990 this had grown to 88.7%, and by 2030 it is expected to reach 92.2%.[5] To address the issue, better designed urban lighting is needed – whether it is street lighting, lighting the exterior of buildings or in public spaces – to strike the right balance between light and darkness. Here are Tamlite’s top tips for achieving this.
If every street lamp in the UK was upgraded to LED, it would save in the region of £77 million
52 | April 2022
Exterior Lighting – Tamlite.indd 52
• Switching to LED lighting: LED lighting is extremely energy efficient. Indeed, the Energy Saving Trust reports if every street lamp in the UK was upgraded to LED, it would save in the region of £77 million.[3] • Design considerations: Poor lighting design results in energy waste, light spill and light intrusion, and the IDA estimates that 35% of artificial light is wasted by being poorly aimed or unshielded.[7] The nature of urban spaces may be subject to considerable variation – from busy side-streets to parks – but it is vital to invoke one universal design principle: that lighting should be highly directional and provided only when and where it is needed. Modern LED systems ensure that lighting is radiated into the right space at the right time, in a way that minimises light spill or trespass. Upward Light Output Ratio (ULOR) describes the amount of upward light distributed from a luminaire. For urban lighting solutions, this ratio needs to be as small as possible, to ensure that the output is angled downwards, only where it needs to be. • Assessing the area: Another key aspect of urban lighting design that also gets largely ignored is the lack of consideration for the individual requirements of a given area. In many cases, standard fixtures can be applied across the board. Yet, it is essential to ensure that the lighting is appropriate for its environment, whether that’s a major road, residential street or a pedestrianised city centre. For example, a high street will typically require a far higher and more dense level of illumination (10-20 lux) than a suburban space that could fall under the remit of dark-sky preservation orders (5 lux). • Illumination levels: The level of illumination at different times of night is key. In the evening, exterior lighting eases the transition between day and night, allowing people to adjust to darkening skies. This is particularly important in the autumn and winter as daylight levels are low during rush hour, and many people are walking to or from work. ‘Good lighting practice is the provision of the right light, at the right time, in the right place, controlled by the right system’ is the introduction to the ILP Guidance Note, GN01/21, The Reduction of Obtrusive Light and goes on to talk about how the control and reduction of obtrusive light is hugely important for exterior lighting. The invention of artificial light and its application in the external environment has done much to safeguard and enhance our night-time environment but, if not properly controlled, obtrusive light (light pollution) can present serious physiological and ecological problems.
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• Colour considerations: When designing exterior lighting solutions, it is also important to take into account the colour of the luminaires installed. For example, blue-rich white light is particularly troublesome when it is excessive, especially in areas where houses are adjacent to commercial properties, because it can impair circadian rhythms and sleep. It is also significantly brighter than most alternative lighting solutions, which increases the level of light trespass and has damaging consequences for both humans and wildlife. By lowering the colour temperature to warmer whites creates a lighting solution that benefits both nature and people.
Better designed urban lighting is needed
The importance of proper planning when lighting urban spaces is bound to become even more crucial as the number of people living in towns and cities grows. Those who want to deliver a safe, attractive, and sustainable environment would be well advised to give lighting due care and attention throughout their urban spaces, working on the basis that a well-specified and efficient lighting infrastructure can be a benefit to all citizens, and the environment, for generations to come. Tamlite Lighting, tamlite.co.uk
https://www.nationalgeographic.com/science/article/nights-aregetting-brighter-earth-paying-the-price-light-pollution-dark-skies
[1]
https://www.nhm.ac.uk/discover/light-pollution.html
[2]
https://www.cpre.org.uk/wp-content/uploads/2019/11/Night_Blight.pdf
[3]
https://www.darksky.org/light-pollution/
[4]
https://www.theguardian.com/news/datablog/2009/aug/18/percentagepopulation-living-cities
[5]
[6]
https://energysavingtrust.org.uk/towards-a-brighter-future-forstreet-lighting/
https://www.bbc.co.uk/news/science-environment-54721921
[7]
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30/03/2022 14:59
