by Per Arnold Andersen, VELUX Group

Daylight is indispensable for the sustainable renewal of our cities. But how do we convince politicians, investors and citizens of its advantages? What means of communication do we need to convey our experience of daylight to others? And how is daylighting design likely to change in the future?

These themes and questions have been discussed in a conversation between Francesco Anselmo, Arfon Davies and Florence Lam from the engineering firm, Arup and the editorial team of Daylight/Architecture from the VELUX Group.

In times of progressive urbanisation, how can we ensure that daylight is prioritised in the development of our cities?

We can learn from the way in which traditional cities adapted to local climate. The shape and density of traditional cities and settlements everywhere depend on the availability of daylight and the angle of incidence of the sun. Earlier, of course, people had to build in this way due to the almost total absence of artificial light. But the question as to how we can make the best possible use of natural resources is more relevant today than it has ever been before.

In a city like Hong Kong, for example, where the densely built-up urban fabric lets in much less daylight than in the cities of the west, natural light was translated into a commercial value at a very early stage; buildings and apartments that receive a lot of daylight are easier to sell and offices with a high incidence of daylight have a higher market value. This is also why Hong Kong has very detailed planning guidelines, which stipulate the distance between buildings, for example.

In London, planning is going in a similar direction. Here, the ‘right to light’ principle applies; it prevents new buildings from taking daylight away from already existing neighbours. Previously, however, it was possible to pay a neighbour a certain amount of compensation in order to circumvent this right. This did not exactly devalue daylight but did make it a commodity and a matter for negotiation. Fortunately, this practice is changing at the present time. New guidelines and regulations are now being formulated that allow the issue of daylight to be handled in a differentiated manner.

The increasing degree of urbanisation both necessitates and, at the same time, is a prerequisite for such new regulations and planning tools. After all, an individual client or architect can only achieve very little in this area. Politicians, as well as urban society as a whole, need to engage themselves with this issue.

In all the world’s large cities, we need to create the awareness of how important daylight is in the present process of urbanisation. This is all the more important in view of the conflicting requirements in the case of many buildings. If the aim is to improve the supply of daylight, this often reduces the volume of a building or increases its distance from others. The lettable floor space in buildings – the aspect that property developers are most interested in – becomes smaller as a result. However, there are strategies for optimising daylight and floor space simultaneously.

It is up to all designers of buildings to sensitise clients and investors to the importance of these strategies. Much of the work of Arup’s lighting designers, for example, consists of conveying the benefit of daylight to others. In this context, it is useful sometimes to consider things from other people’s point of view. Architects tend to understand the value of daylight for human well-being immediately. Property developers would perhaps listen to this argument but, in order to influence their decisions, we have to offer them some tangible added value. If, for example, it can be shown that they can have more floor space in buildings through an interactive process of design and optimisation and yet still meet all the requirements in respect of urban planning and daylight, the whole thing becomes interesting for them.

The term ‘value’ is of interest because it is often used in the communication between designers and clients. Usually, people spontaneously take it to mean monetary value. But, in reality, values are primarily to do with people.

Indeed, we would systematically misunderstand many of the non-monetary values – whether this is health or happiness – if we tried to count them in figures.

In this context, it is worth remembering the prophecy made by the Cree Indians: “Only after the last tree has been cut down; only after the last river has been poisoned; only after the last fish has been caught; then will you find that money cannot be eaten”.

How do we introduce greenery to our cities? How do we use solar energy? Where and how do we create shade in urban areas and what would life be like under treetops created by people?

At the heart of sustainable urban development, there is a simple question: what do we actually need to survive? This includes forests; the way in which we are developing our cities and cutting down forests today has a considerable impact on our ecosystem. With every hectare of forest that is lost, evaporation decreases, there are fewer clouds, the atmosphere becomes warmer and the CO2 level rises. Would it not be possible for us to transform our cities into man-made forests, with surfaces that, like trees, filter light, use the energy of the sun and improve the microclimate? This would elevate the importance of daylight in the city and immensely improve the quality of urban life as a whole. In many cities, consideration is already being given to how sunlight could be used in this way. Large surfaces of buildings could be clad in photovoltaic panels or have vegetation planted on them. If such methods were to be adopted, the availability of daylight in the city would acquire a completely new significance. Our cities would not become real forests but possibly metaphorical ones, designed by people according to the principles of biomimicry.

A lot of things that used to take place organically now have to be planned carefully. Today, the control of land is in the hands of politicians, planners, investors and lobbyists. They decide what is built and have the opportunity to shape our future with good ideas. But they also bear the responsibility for doing this in a way that really does justice to human needs.

“The great challenge for us designers is to make our clients understand that money is not everything and that, sometimes, it is worth investing more to generate benefits for human beings. This is not easy, of course, but I see this as a great task that we share for the future: giving people in buildings priority over money.”
Arfon Davies

What are our basic needs? What kind of comfort do we strive for – and what consequences does this have for daylighting design?

At the end of the day, these questions are central to any building design process. It seems that we are no longer planning buildings for individuals but for standardised average persons. Quite often, today’s buildings tend to have an indoor temperature that is constant over the whole year but it tends to be too high, thus fostering illness. Perhaps, we should allow ourselves a little less ‘comfort’ in this static sense and expose ourselves more to the fluctuations of the natural climate and sunlight. We should much more often let people choose the kind of climate they would like to live in – both indoors and outdoors.

In daylighting design, for example, we often consider glare as something negative. However, it could be seen positively as well; people stand up when they are dazzled by light and move to a different position in relation to the sun. In this way, glare could be made into an activating factor that changes personal behaviour.

So we are facing two tasks at the same time: to change our cities with the help of daylight and, at the same time, to individualise them. We may, therefore, need to abandon the ‘international style’ of recent decades. It has made cities the world over look exactly the same, without any relation to the climate, the sun or even the local culture. But where can we make a start in changing things? Would it be possible to develop a differentiated vocabulary for openings used for daylight and ventilation in buildings so that the existing ‘one size fits all’ buildings can be re-designed and reshaped?

What tools are available to architects and engineers for daylighting design today? And how could these tools be improved?

Talking about tools, we shouldn’t forget the past. Many young designers are very enthusiastic about computers and computer-aided simulations. However, we should also value the physical, manual tools previously used for working.

It has been very important for Arup to nurture this ‘craft’ of daylighting design – and with it, the intuition regarding daylight that can only be acquired through attentive observation, absorbing sensory experience and engaging in experimentation.

The best tools we have are our senses. But people today often look at buildings and rooms through cameras – and through the pictures they make – rather than with their own eyes. At the same time, all outstanding architecture involves spatial and sensory experience, which can only be had in situ and with sufficient time being allowed. It is essential to re-acquaint architects with this insight.

This also applies to the schools of architecture, where we are experiencing a wave of parametric design at the moment. This design practice focuses closely on form and geometry, but are the new computer- aided tools also well suited for the selection of materials? The question as to how materials interact with light and how they are perceived, for example, can only be answered by means of observation.

Thirty or forty years ago, architecture students were encouraged to develop an instinct for daylight and its qualities in different parts of the world. This part of their education has become somewhat neglected today. Nevertheless, it is still useful to improve one’s powers of observation, boost the imagination and
acquire an inner receptiveness. Facts and figures are great when it comes to precision and, of course, we have to corroborate our concepts. At the beginning of every design, however, imagination should come first.

Essentially, every tool is appropriate in the design process – but the timing is what counts. Furthermore, what matters is taking time to become closely familiar with the tools and sometimes calling them into question.

The Arup lighting team uses design tools according to this principle. At the start of a design process, there are open questions arising from the design – for example, when the architect has designed a particular shape of building that Arup wants to optimise in respect of daylighting. In such cases, the team often develops special tools, because standard software does not offer any solutions. This is what can make a project fascinating – it is necessary to be creative and develop your own spirit of research.

The Arup lighting team starts many projects in a very conceptual manner, with a sketch or an inspiring image. Then the work is continued with a physical model relatively soon after. In many of their projects, especially museums, the lighting designers insist on seeing spaces in a model or even on a scale of 1:1 before they are actually built. To Arup this is the only way they and their clients can really experience the effect of light. With numbers alone, this would be impossible.

“We should strive for a variety of spatial situations in which users can make their own choices. Here there are close parallels to urban planning, which is currently turning away from the monofunctional urban districts of the past and trying to generate a smallscale, more vital mix of living and working. Now is the time to promote such ideas; people all over the world are learning to re-assess the value of variety and local identity.”
Florence Lam

What potential do digital simulation tools offer?

Computer simulations can be useful, particularly in very early design stages. The level of daylight in a room often has to satisfy certain minimum requirements, for example. With computer simulations, it is possible to judge at a very early stage whether you are on the right track. The VELUX Group has developed such an intuitive program, the VELUX Daylight Visualizer. The program is intended to enable architects to maintain control over the daylight and the indoor climate instead of delegating these matters to specialists.

Computer programs can also play another important role: if we want to express daylight’s variability over time and in a space, enormous amounts of data are created. The challenge will be to process this data digitally so that people who are less used to working with computer models also understand it.

Furthermore, computer simulations are useful for developing and doing the calculations for a large number of design variants. The problem here is that it is easy to make big mistakes, which would not be possible with the physical model. Quality control is therefore essential wherever simulation tools are used.

To the Arup lighting team, one of the most valuable tools is a collection of interior photos of their previous projects, which they use as references for future designs. This includes not only conventional photographs but also HDR (High Dynamic Range) ones, showing the luminance distribution in a space. With the help of such pictures and the spaces they show, it is possible to give clients an impression of what daylight quality they can expect to encounter inside their own – yet unfinished – buildings.

The Arup engineers also gather their own climate data at locations where they are planning buildings. Although weather and climate data exist for many places all over the world, they are not always precise or available to everyone. Arup’s measuring instruments are comparable with Mars Rovers, which are set out in very different places and that supply the designers with data for a year or longer. The data is rather simple – the ratio of direct to diffuse sunlight, for example – but it is reliable.

How do we make our data and tools generally accessible so that everyone is able to participate in the knowledge of daylight?

We have to reach many more people than today if we want to make our cities more sustainable and people-friendly. We must sensitise not only individual architects, but also investors and housing construction companies to the issues involved – as soon as possible.

When you want to repaint your bedroom at home, for example, you usually consult one of these RAL colour charts with hundreds of different swatches. It would be interesting to develop a similar chart or a picture book with hundreds of light moods from which people could make their choice. This should be a simple tool, a collection of best-practice examples. In fact, many different books would be needed – a different one for every climate and every location.

In the context of the latest International VELUX Award for Students of Architecture, the VELUX Group asked each of the participants invited to the award event to bring along his/her own ‘magic daylight moment’ – in the form of a photo, a poem or whatever. The task was then to talk about one’s own special ‘magic moment’ to the other participants and try to jointly develop something like a collective daylight moment – a situation in which daylight brings people closer together. Would it be possible to develop a tool with the help of which people could communicate their own daylight moment easily and fairly precisely? It could act as a catalyst for the transformation of our cities.

We take daylight for granted in our everyday lives. But will our children still be able to do this? Will they have enough daylight?

The British neuroscientist Russell Foster advises us to take a ‘photon shower’ every morning to adapt our biological clock to the rhythm of nature. Today, the need for this is often forgotten. In former times, people used to work mainly during daylight hours, sleeping longer in winter than in summer. Perhaps, this would be a more natural way of life that would be better for us. In any case, we risk a feeling of permanent jet lag unless we adapt our rhythm of life to the rhythm of the sun and recognise its signals.

The situation also has a crucial social component. We allow people to follow a rhythm of life that is unhealthy for them. At the same time, we often force them to do so. In the world of work in particular, many processes have speeded up to such an extent that people are frequently compelled to work in the evening or at night – rather than during daylight hours.

So maybe we do not only need a new culture of building but also a new culture of time.

If we learned to be aware of daylight in all its nuances, this would certainly be a first step in the right direction.

“We have sufficient daylight and will probably still have enough in future but not necessarily of sufficient quality or at the right time in the right place. Even now, we spend most of our lives in buildings where the level of daylight is not necessarily conducive to health. Perhaps, we will assign greater value to daylight in future for just this reason – because we will have less of it in our everyday life.”
Francesco Anselmo

What role can future standards and guidelines play in order to supply people with daylight more effectively?

The fundamental problem is that the time variable is missing from current building standards. We have made progress in moving beyond previous, static methods of measurement such as the daylight factor, which only considers diffuse daylight. But there is still a lot to be done before we have understood the fluctuating nature of daylight sufficiently to incorporate it in standards and design criteria. This concerns not only the climate-dependent variability of light but also the individually different needs of human beings.

A good tool or a set of rules is one that answers the crucial questions. And, in the case of daylight, these are: can I work under certain lighting conditions and do I feel comfortable in doing so? Future standardisation will have to address these questions. So far, standards often tend to be a result of lobbying and the intention to sell some product or other; they are less frequently aimed at improving living conditions.

How will the practice of daylighting design change on the whole?

We have a great opportunity to revive the forgotten art of daylighting design in architecture. Let’s hope that the profession of the daylighting designer will become established in architecture – as a specialist right at the beginning of the value chain, whose advice clients request at the very start of a project. At the moment, the problem is that many specialist planners are consulted much too late, i.e. when they can no longer exert an influence to generate added value for the building.

Furthermore, daylighting should be made into a mainstream issue. We must ensure that daylighting design does not become a hermetically-sealed discipline that is excessively fixated on figures. If we want to make daylighting into an everyday issue, we must speak a language that people understand and with which they can intuitively gain access to the topic!



Francesco Anselmo is a Senior Lighting Designer at Arup in London. He holds a PhD in Environmental Physics and a degree in architectural engineering. He is an expert in numerical simulation and visualisation systems and develops computer tools for lighting design, building simulation and interaction design.

Arfon Davies is a lighting designer and Associate Director within the lighting studio of Arup. He has particular interest and expertise in the design of daylighting systems for projects in all parts of the world. Arfon has authored the daylight section of the British Council for Offices lighting guide, soon to be published, and is also a member of the committee rewriting the UK’s Society of Light and Lighting guide for daylight and window design.

Florence Lam is a Director with Arup, where she leads the global lighting design practice. Her particular interests in visual perception and natural lighting have played key roles in many of her design solutions on projects, such as the Tate Modern in London, the New Acropolis Museum in Athens and the California Academy of Sciences Building in San Francisco.

Per Arnold Andersen is Head of the Daylight, and Indoor Comfort Knowledge Centre in the VELUX Group. He worked for more than twenty years as an architect and planner before he joined the VELUX Group. He is active in European lighting standardisation and has been co-organising the VELUX Award for Students of Architecture and the VELUX Daylight Symposia since 2004.

Christine Bjørnager is communications advisor in the VELUX Group, working with corporate communication, corporate strategy communication and key messaging. She is responsible for communications in International VELUX Award for Students of Architecture and has been part of the editorial team of the magazine since it was issued for the first time in 2005.

Lone Feifer is Programme Director for Sustainable Living in Buildings in VELUX. M.Arch. and postgraduate Master in Energy and Green Architecture. Led the award-winning VELUX Model Home 2020 demonstration project programme, engages internationally into operational and strategic elaboration of sustainable buildings with holistic focus; Lone is an active panelist, speaker and educator.

Torben Thyregod is concept developer spearhead for sustainable transformation in the VELUX Group. He has worked with radical innovation and a holistic approach, bringing a cultural context to natural elements. He has initiated a number of prize-winning and thought-provoking films about people and their dependency on light. He started the Nordic magazine, DAYLIGHT in 2003 and has been responsible for the layout of D&A, since the first edition.


Article from D/A Magazine issue 19, the full issue is available at