Glowing like fireflies

As one of a small number of lighting design offices, we also have the option to produce luminance images with spatial resolution. With these images, we can record the contrast conditions on the building in detail and thus clearly determine the brightness values required from a perceptual-psychological point of view. In doing so, we only use as much light as is really necessary, which is then more beneficial for the architecture and also for the environment. Less is simply more.

By environment, you mean the issue of light pollution. Many people are not yet familiar with this term. What does it mean?

This is a very complex term. Most people understand it to mean the exorbitant amount of light that causes urban sky glow, the light you see over a city at night. But you actually have to divide light pollution into other categories.

For example, light trespassing, which occurs when certain light sources are incorrectly positioned or oriented. You might want to illuminate a roof edge, for instance – but instead of lighting up just the roof edge, you end up directing a portion of light into the sky as well. Glare is another such category. It refers to the physical or psychological dazzling of people by light. Then there are cluttering effects. Clutter occurs when multiple light sources are simply planned incorrectly and placed too close together, thus emitting an unnecessarily excessive amount of light. In the end, it all results in excessive illumination, which leads to a whole host of problems for many organisms.

One of the consequences of light pollution is that the Milky Way can only be seen in remote places in the world, and the starry sky in general is becoming increasingly faint. This could perhaps still be tolerable.

As a human being, you could maybe learn to live with it. But migratory birds, for example, navigate using the stars. And if the view of the stars is no longer available, they can no longer do this. More importantly, the biological clock is thoroughly confused by light pollution, especially by an increased unnatural amount of cold white light with a high blue content. This applies to humans as well as to birds, insects and other organisms that coordinate their activity using this light-dark phase.

Because artificial light makes everything brighter for longer, the active phase of insects is prolonged. This means that they consume more energy than they take in, which can be fatal. Light pollution also has direct negative effects on humans. Not only can light be unpleasantly dazzling, especially when there are strong contrasts at night, but too much artificial light at night can also lead to suppression of melatonin production, which studies have linked to diabetes, cancer and heart attacks.

Birds estimate which season they are in based on the lengths of the day and night and then determine when to breed. Early breeding can have negative effects on the offspring, especially if this takes place in the cold winter months. Light rays from illuminated or backlit façades also attract birds, which repeatedly leads to mass collisions. All of these are just examples. Ultimately, a whole bunch of negative ecological changes are produced.

There are also differences in the perception and effect of light between humans, birds and insects. For example, luminaires that appear less bright to the human eye can appear extremely bright to insects.

Yes, insects generally also perceive the blue content in the light spectrum much more strongly. That is why they are more attracted to light sources with a higher blue content in the spectrum and why warm white luminaires are better in principle. But there's a paradox to this: The colour temperature does not necessarily correlate with the blue content of a luminaire. To the human eye, for example, a luminaire with 4000 Kelvin looks cooler than one with 3000, but this says nothing about the blue content. Thus, as a planner, you actually have to take a spectrometer to hand before planning any luminaire, in order to find a reasonable ecological solution. The situation can be even more complex with regard to flora, as there are tree species that are sensitive to the red content in the spectrum.

We can therefore only ever find solutions with a compromise; there is no scenario in which you will satisfy every condition 100 %. The world is too complex for that, with too many protagonists. For each project, we look at the surroundings, communicate with biologists and – as unfair as it may sound – we then draw up a list of priorities. Conflicts of interest still remain. The other solution would be to turn off the lighting completely, but that is not possible in many cases. Especially not with street lighting, when we are talking about safety-related illuminance levels.

How can the extent of global light pollution be measured?

Using satellite images. They give a good overview of the total amount of radiation being emitted towards the sky. What the satellite images don't show you, however, are the solutions. For example, you might question why one street is so much brighter than another.

For your study on light pollution in metropolises, you therefore also travelled directly to cities such as New York, Toronto and Warsaw. What causes of light pollution were you able to identify?

The causes are very location-specific, and each city has its own problems. It is often not possible to identify them with the naked eye. Quite often, certain streets look relatively dark. But if you then look at the luminance image and relate it to the street cross-section, you suddenly notice that Boston, for example, has more light emissions than New York.

So the bright shop windows in New York are not so bad because of the high buildings and the many absorbing surfaces?

If we are only talking about the urban sky glow – the light that goes into the atmosphere – then yes. The light from the shop windows in New York is carried into the urban space and then you have quite a lot of surfaces that have the potential to absorb the light. However, the light that is generated down there also attracts insects, so it still remains a problem area.

To compare the metropolises, you developed your own evaluation standard called "weighted urban total luminance". The results showed that Warsaw produced by far the most light pollution of the cities studied, even more than Boston and New York. That is surprising. What's the reason for this?

As far as measures against light pollution are concerned, we can already deduce a lot from what you have said so far.

The best solution is dimming – I cannot emphasise that enough. It is the biggest factor, as reducing the overall amount of light has a bigger impact than reducing just the blue content. For the ecosystem, of course, it remains best to have no artificial light at all, but you have to find a compromise between relevant lighting and ecological aspects.

A very strong measure would also be to plan and implement projects sensibly, i.e. by looking at the needs of the planning area beforehand and planning accordingly. This includes the aforementioned spectral analysis of the light sources. It is then very important that the light points are, in the best case, not visible at all and positioned relatively far down, so that insects are not triggered by a distant light point in the first place. It is very much about making light invisible and only having light where you need it. Time also plays a factor – so again, dimming is important.

No part of a beautiful building façade needs to be illuminated if there are no people around. This is not only highly questionable in terms of light pollution, but also in terms of electricity consumption. If you have a plan that is very good for the ecosystem, then it is usually also a plan that is very economical because it will consume less electricity. Thus, it's important to consider dimming here as well – or, if possible, to switch lights off completely.

You write in your study that, in your view, urban spaces do not have to have the same appearance at night as during the day. Lighting design makes it possible to reduce light pollution and still create urban identities. You take fireflies as a model for this.

Yes, I think it's a stunning example, and that's how I personally see light planning. A firefly looks different during the day than at night. During the day, it looks like any ordinary insect, and some people might even be disgusted by the appearance of the firefly. But in the evening, the insect seems so magical, even though it's really only a point of light that people are fascinated by. You only see a fraction of the insect, and that's a philosophy I like to adopt in my lighting designs.

When you look at a church, it appears imposing and beautiful during the daytime. But why do you have to present it in the evening exactly as you saw it during the day? It is much more charming to highlight special architectural elements, so that you can experience the churches in a new light. Then, on an emotional level, perhaps the same thing happens as with the fireflies: You get slight goose bumps because the whole thing looks a bit more sublime.

During your study, you were also able to find positive examples – such as the High Line in New York, the track bed of a former elevated railway, which has since been converted into a local recreational facility.

I don't know if the lighting designer had the ecological aspect in mind, but what was simply very positive were the low light points that were used there. The whole thing is very cleverly planned. The idea was to present the city of New York itself, the urban environment, as a stage. This means that when you are on the High Line, you don't want to be dazzled. The light points there are therefore so low that even people in wheelchairs cannot see them. Of course, this also has a good ecological aspect, because the light points are also less visible to insects from a distance.

Reducing light pollution is also a focus of your own projects as a lighting designer. Most recently, in a team with several partners, you came in 2nd place in the nationwide "Reallabore Innovation Award", awarded by the German Federal Ministry for Economic Affairs and Climate Action. How and where did you succeed?

The project is in Heiningen, a small town in Baden-Württemberg with about five and a half thousand inhabitants. What was actually a relatively small project has turned into a study that is now supported by the Baden-Württemberg Ministry of Transport. Originally, it was about planning the street lighting for the through street in Heiningen with new LED luminaires. Then came the idea of making it even more efficient and ecologically compatible with dimming. This turned into a one-year long-term study, which had never been done before.

There were different ideas on how to control this dimming: Whether to simply dim the lights over time, i.e. take dimming value XY from 10 pm and dim them up again from 4 am, or whether to dim down when there is less traffic. In other words, dimming that adapts to the flow of traffic, in the hope that this will be even more efficient and ecological. We decided to test both options. There are therefore measuring points without dimming, with time-dependent dimming and traffic-dynamic dimming. The study then consists of a technical and a biological part.

Maybe explain the technical part first.

The technical part first dealt with how we can actually measure the flow of traffic. We tested three approaches for this. One was tracking via Bluetooth, which records how many Bluetooth devices are on the move. This assumes that the driver of the car has a smartphone and that the car may also send Bluetooth signals itself. The second method was an infrared camera that picks up the heat from the cars. The third method was the evaluation of TomTom navigation data. All the methods were relatively good, but Bluetooth tracking emerged as the winner in the end.

Then it was about finding out what was more efficient: the street section with time-dependent dimming, or the one with traffic-dependent dimming. The results showed that traffic-dynamic dimming was marginally more economical. It must be noted, however, that this study concerned a relatively short through street. If the project were to be scaled up, traffic-dynamic dimming could make even more sense.

The biological part was then about insects.

That's right, insect tracking. We wanted to know how many or how few insects were attracted by the dimming or non-dimming. We did this at three points: in the city centre without dimming, and at two other points with static, time-dependent dimming by 50% between 10 pm and 4 am. To do this, the locations of course had to be comparable, both in terms of lighting technology and biodiversity. We got in touch with a biologist who confirmed the biological comparability of the sites.

For insect tracking, we have developed a novel method with the camera manufacturer. In the usual procedure, a transparent plastic body is suspended underneath the head of a street lighting luminaire in which the insects become trapped and eventually die. It also distorts the illumination or the light distribution curve through its reflections and may therefore attract more insects than the luminaire alone would. This is an unjustifiable method, both in terms of lighting technology and ecology.

And what was the result of the insect tracking?

We collected more than 350,000 data sets over the course of a year and these are still being analysed, so the overall result is still pending. However, we did analyse a random sample, and this sample strongly confirms our hypothesis that less light also attracts fewer insects. This is also confirmed by other studies.

At the measuring point without dimming, we recorded a good 700 insects over a period of one month. At one of the other points with time-dependent dimming, 200 insects were recorded. However, this second point was still located close to the point without dimming and influenced accordingly by its illumination. The third point was situated a considerable distance away with time-dependent full dimming, and only 84 insects were recorded here. This results in a win-win situation: It saves electricity and preserves insect life at the same time.

It's a great project – and the mayor of Heiningen also views it as a pilot project for larger-scale projects.

What I really enjoy is working out the compromise solution – and a different solution is needed everywhere. No one project can just be copied onto another. All the detective work, the coordination work involved; it's exhausting, but motivating.

We are currently developing another interesting project in Amsterdam. There, we were given the task of illuminating all the windmills. These windmills are not always found in an urban context, but are often located in environments where there are many natural spaces. Some windmills are also in the Natura 2000 area, i.e. a nature reserve. This means that the illumination there should be designed with a major focus on preserving the ecosystem. Here too, our solution is accordingly to dim down the lighting design as much as possible.

How did you proceed?

For this project as well, we wanted to emphasise the architectural gesture. We asked ourselves: What is the most important thing about a windmill? For one thing, it's the area where the blades of the wind turbine come together, known as the shaft head, because this is often very beautifully decorated. And of course, the body is something of a defining feature as well.

That certainly sounds efficient.

A compass is built into the upper, rotating part of the mill for this purpose. The compass indicates in which direction the mill is currently turned and passes the signal on to the individual luminaires. These are connected to each other wirelessly. And based on the compass data, only the luminaires that are supposed to light up are the ones that come on. If the shaft head is located between two luminaires, they each shine with 50 % light output. This means that light is only produced where it's needed. This is another mini-project into which a relatively large amount of brainpower and engineering has gone in order to produce as little light as possible. And it's also a new development that does not exist on the market.

As for all other projects in general: DALI ballasts are standard in the luminaires that we use in our planning. We have stored a dimming scenario for every outdoor lighting project that we plan. There is no project where the lighting runs at 100 % all night. There is always a point in time when the light is dimmed and, depending on the building or object, usually a second point at which all the lighting goes out.

Light pollution also plays a role in indoor planning. Presence detectors, for example, switch off the light when there is no longer anybody in the room or dim it down to an orientation light. But there are other aspects to consider, as you outline in your study.

The building should always be planned from the inside out. This includes not only the lighting technology, but also the materials used in a new building, for example. In this regard as well, we have had interesting projects in the past where we were able to play around a lot with the materials and thus reduce light emissions. This is not just about low-reflectance materials – it's much more far-reaching and complex.

One project was a glass building. For the façade, we used glass that filters out the blue part of the light spectrum – that's truly interdisciplinary work there. I think a lot of people just don't realise how the light leaves the building and that it has a huge impact. Of course, glass that filters out the blue content is worth its weight in gold.

Are you proud of your work?

Yes, in retrospect. What bugs me a bit is that at the end, I often think that it could have been done better. But, in general, I am very proud of the projects, especially if there is a certain degree of innovation involved. And the environmental aspect is a great motivator.

Mr Goronzcy, many thanks for sharing these interesting insights.