The Interview
Q1: The availability of daylight and its impact on daily life
How does the availability of sun light impact our everyday lives?
Paul Rogers:
Just about all living things are built to respond to light. The image of sunflower tracking the sun by day comes to mind, but humans are every bit as sensitive to light. By light I mean that over hundreds of thousands of years of evolution our natural biorhythms are very much in tune with the earth’s cycles of light and dark both diurnally and seasonally. Some of us are more sensitive to these circadian cycles than others but the amount to which we are exposed to natural light affects everyone to some extent. Generally speaking, people become more aware of this connection as the seasonal differences in light exposure become most pronounced. It is interesting to see how even 10 degrees of latitude can make a difference to how people value light. I’m originally from Canada. Like many Canadians, I grew up around an hour or so from the US border. This place was around 49° latitude. People are aware that it gets darker in winter, but seasonal effects of lack of natural light are not frequently discussed. Rather, during the winter, discussions tend to be focused on the cold and maybe even the snow.
In Canada, winters are normally very cold but for wide swatches of the country they are also relatively sunny. With the cold air there is little humidity and this means that there is often a crisp light. And for much of the winter, this light is normally reflected off snow. But there is also the fact that more than half of the population of Canada live in detached single-family dwellings. With this kind of climate combined with low-density development, people are getting enough natural light indoors.
In the UK and Scandinavia, it is more common that people live in apartment buildings in urban areas. And then in the UK the skies are often grey and cloudy. That, in combination with urban density, means adequate access to natural light becomes a challenge. But the UK’s location latitudinally is still not high enough that you have the winter darkness in the same way as you do in Scandinavia. If you look at a map you see that Edinburgh is at a similar latitude as Copenhagen but also that Helsinki, Oslo and Stockholm are much higher up at 60 degrees latitude. This means that for the majority of people in the UK, the winter will be much different than it is for Scandinavians.
When I first moved to Sweden, despite my background in working with climate, I didn’t really realise just how dark it would be. Unless you've experienced the grind of the dark Scandinavian winters, you can’t imagine how it is. At that time of year, even when it is sunny there’s still very little strength to the light. With the sun at about six degrees above the horizon at midwinter, the sunlight is not only weak, but it also causes very long shadows. This, combined with the tendency for higher urban densities, certainly effects how people think about natural light.
Tony Olsson:
The fact that light is an important aspect that affects the body and soul of Scandinavians is noticeable when, with the first warm day in early spring, people rush outside to sit or stand in the sun. You can even see this in the winter months. As soon as there is a beam of light, people go directly to it. We know the positive impact the light has on the body. We can feel it. We want to take advantage of the light that is available as we know it gives us energy and well-being.
Q2: How has the availability of daylight in Scandinavian countries impacted building design over the years?
Paul Rogers:
In Scandinavia around the1930’s, 40’s and 50’s, there was a real push to prioritise public health. Provision of natural light and fresh air became central considerations in building design.
Over the past decade, I have been involved in a number of studies examining daylight levels in Sweden's existing housing stock. The first of these studies was conducted in 2018 and examined 75 residential buildings: in total of around 15,000 rooms. What we found was that buildings constructed during the 1930’s, 40’s and 50’s generally had good daylight performance. These buildings were generally well spaced and had large windows with rooms of limited depth. At the time, electricity was commonly available, but it was generally expensive, so it was an economic necessity that provision of daylight remained a priority.
In the 1960’s electricity became increasingly affordable for the average family. And this becomes reflected in building design as room depth started to increase. Through the 60’s and 70’s daylight access was still given high priority in planning. But with the late 70’s and early 80’s came the energy crisis and while the deep rooms persisted, window size became reduced. The result was dark interiors. With the 90’s there came a backlash and for a time window sizes became very large. As a result, overheating became a problem and through the 2000’s we have seen a return to the concern for energy use and thermal comfort. And with that comes the pressure again to reduce window sizes.
While concern with energy and overheating is a common theme through much of the world, Scandinavia perhaps is unique in that it also has the extreme challenge when it comes to getting enough natural light. Finding balance between these two opposites takes careful consideration.
Tony Olsson:
The winter season is a long one and this means that we are indoors a lot. But even from within the building, we want contact with the natural world, and this has shaped building design. It is not only the size and location of the windows which is crucial, but the desire to bring in the light that has also affected how we orient our rooms and even our choice of interior finishes. Much of what we commonly associate with Scandinavian design is an attempt to allow more daylight into the building. It makes sense then that, concern for daylight is more evident our building stock than it is elsewhere.
Q3: Achieving maximum natural light and boosting sustainability
Interviewer: A lot is said about natural daylight and maximising of solar gains during the winter months to save energy and boost sustainability, but what are the facts around this?
Paul Rogers:
Maximising passive solar gains for heating in winter is not as prominent a strategy in northern Europe when compared to other climates. In the UK, you have a lot of cloud. In Scandinavia you have cloud but also very limited sunlight hours during the coldest parts of winter. What little sun there is during the winter goes through a think chunk of atmosphere because of low solar angles so at the time of year when you need it the most, the sun just does not contain a lot of energy. So passive heating, while it can be of some benefit in the spring and autumn, not much focus is given to this strategy in Scandinavia. Rather, to my way of thinking, it is better in Scandinavia to maximise the thermal resistance and air tightness of the building envelope so that additional window area can be found for provision of daylight.
Rather than passive gains, for Scandinavia I think it is more important to balance daylight with protection from overheating. Not a lot of people realise this but in Scandinavia the solar loads on windows are quite high. It is easy to be fooled by the cooler summer temperatures but the low path of the sun in the sky means that the sun meets a vertical window at angles which are closer to the normal (90 degrees) and this brings substantial energy to not only south but also east and west facing windows. In comparison, at lower latitudes the summer sun will be much higher in the sky and with a more obtuse angel of contact with the window, the solar energy on the surface of the window will be less intense. So, there is more of a challenge in Scandinavia than you would think.
We should also keep in mind that in Scandinavia, the path of travel of the sun around the horizon during the summer is extreme. So, the higher the latitude, the less effective fixed shading becomes. And then also consider that a fixed shade will reduce the amount of daylight for the entirety of the year. This is something you don’t want in a predominantly cloudy climate with prolonged winters. So, a truly passive Scandinavian approach is large windows to harvest daylight during the darker months, and then an operable shade to reduce glare and solar gains from low angle summer sun. And this is traditionally what is done in practice. In Scandinavia, for housing this has generally meant interstitial venetian blinds and for commercial application the more recent trend has been towards interior mounted roller shades.
With the window sizes normally used in Scandinavia, internally mounted shades will frequently need to be metalised to meet the challenge and often this is not even enough. In terms of daylight and thermal performance, an external operable shade is normally the best option. So for Scandinavia, I don’t think you can talk passive design without basing the conversation on operable solar shading.
Tony Olsson:
I agree completely that for Scandinavia, operable shading is by far the most effective solution. And sun shading, when operable, is best motorised and automated. The better the control, the smoother and more effective the system in relation to building requirements and user needs. Using a control unit that measures not only sunlight but also the movement of the sun throughout the day and can recognise when light hits different parts of the façade is very important. A controller that can read where shadows are on the property allows for dynamic control and this ensures that sunshades are activated only when a room needs it. And then beyond this there is a human aspect as what is best for the building at a particular moment in time may not meet our individual needs.
It is very important that the tenant feels that they are in control of the system and that it is responsive to their needs. Locally placed controls for temporary override should be installed but it is also important that automatic control takes over again after a certain time. You want your solar shading to anticipate when you need protection, relinquish control when the user wants something different and then finally hop in and take responsibility to reset the system without anyone taking notice. It sounds easy but getting a system to respond in this manner is something we have put a lot of effort into for a long time.
It comes down not only to the choice of control system, but how it is managed. With the right control parameters, we get better thermal comfort and reduced cooling loads of course but there is also the possibility of using the sun shading as an active insulating layer at night. Solar shading can also help to keep a property warm in the winter. This maybe seems counter intuitive but an activated solar protection during the night, or even when there is no one present, helps to hold heat. By reducing heat loss from windows in this manner, solar shading can potentially work to allow for larger glass areas than that which would be possible otherwise. These are the sort of questions which need to be discussed already early in the design process, however.
If solar shading is only added to the design late in the process you are likely to miss the full benefits it can provide to daylight and indoor climate. Also, when considered as part of the early design phase you are more likely to achieve a smart installation that is integrated architecturally to the design and with controls best matched to the needs of the tenant. Technical performance, functionality and user satisfaction must harmonise if solar shading is to live up to its true potential.
Q4: Planning and regulation.
Interviewer: How important is regulation, compliance and planning when it comes to design and how does this influence the technical decisions made in building design?
Paul Rogers:
Regulations are extremely important. Without them, there is little incentive, and other aspects will be given priority. There are so many factors that need to be considered in making a building. So unless something is stated as a legal requirement, in the vast majority of cases that thing will not be given sufficient attention. In many cases it may even be forgotten completely.
Code requirements for daylight have existed across Scandinavia in various degrees for over 50 years. Sweden is the country where compliance with daylight regulations is most actively enforced by the authorities, but Denmark and Norway are very also active. Normally, the requirements are applied at the time building permits are issued but over the past decade, we have also started to see an increased awareness already in the planning phases.
Traditionally, Iceland has only very simple requirements for daylight but in recent years, more densely planned developments has led to the proposal for regulations more in line with what you see in Denmark, Sweden and Norway. The situation in Finland is quite an interesting one. Though daylight has traditionally been a priority in Finland, there is currently no daylight legislation other than general guidelines governing window to floor area and minimum distance between buildings. A recent study showed, however, that with increasing urban density in the country’s urban centers, daylight levels were often insufficient.
Natural light is universally valued of course, but the UK differs considerably to Scandinavian with regards to the priority that daylight is given in design. In both Scandinavia and the UK, the legislation implicitly expects planners to consider daylight and sunlight as an aspect of quality of life. But later on in the building process, the approach starts to differ. The British Research Establishment (BRE) has for many decades done groundbreaking research on daylight assessment of buildings and though some town councils reference their guidelines, there are no explicit mandatory requirements for minimum levels of daylight in either England or Wales.
From what I understand, Scotland’s legislation does recommend a minimum of 7% glass to floor area, but this kind of simplified assessment doesn’t really ensure adequate daylight as it does not account for surrounding obstructions. And with the pressures that the UK is facing to build densely, I think the situation has become very difficult. So much so that a few months ago, a delegation of experts met with politicians to discuss the situation.
It shouldn’t be missed however that in England and Wales, there is a very well established ‘right to light’ legislation. This legislation is separate from planning law and serves to help protect daylight access for existing properties. The Scandinavian countries don’t have as well-defined legal system for such cases. Rather, in such disputes the judiciary tends to find their way on a case-to-case basis without much concern for technical reports and often defer responsibility to the planning authorities. My hope is that the Scandinavian countries will eventually adopt a framework for protection of existing properties similar to the one currently in place in England and Wales.
But returning back to the subject of new buildings, whereas in the UK natural light is treated as a best practice recommendation to be optimised within practical limits, the Scandinavian approach has typically relied on defined prescriptive minimums. In other words, while the UK tends to approach daylight as an amenity, the Scandinavian approach has been to treat daylight as a necessity, an essential part of healthy living.
Tony Olsson:
Regulation has also had an effect here in Sweden with regards to the use of solar shading. It has helped to point out the necessity of shading solutions like automated solar shading. The building codes in Scandinavia are generally quite ambitious with regards to energy performance. To meet these strict energy targets, you need to seemingly make use of every tool at your disposal. It means that shading is normally regarded as an essential part of the building design. It is not uncommon that solar shading is integrated to the aesthetics of the building design.
Health concerns associated with overheating has been a particular focus of conversation recently. In Sweden we’ve seen the introduction of new regulations from the public health agency to prevent overheating. These regulations allow for building interiors to exceed 26° degrees Celsius only for short periods of time. This new regulation puts additional responsibility on property owners and landlords to keep the indoor climate at an optimum temperature. In order to meet the targets set by the new regulations some of the larger property owners have now started looking at various solutions, such as the retrofitting of their existing dynamic solar shading systems.
Generally speaking, the new regulation has put focus on how control systems can optimise performance. It´s not only how the system manoeuvres the shade up or down when sun is shining. Rather, with these regulations solar shading and their control systems is now considered within the wider context of its effect on indoor climate and human health.
Paul Rogers:
I would just like to add that these new requirements from the public health agency also potentially affect compliance with daylight regulations. Although much of the regulatory framework for daylight within Scandinavia fails to account for reduction in daylight due to deployment of solar shading, there are some pieces of legislation which are based on the European daylight standard (CEN 17037:2018). One such regulation is from the Swedish Workplace Safety Authority where according to the 17037:2018 reduction in daylight from operable solar shading should be accounted for.
In practice, compliance with both this legislation and that of the public health authority is not yet part of common practice but there is a legal framework which suggests that we should be working more in depth to balance overheating with daylight than we currently do. The importance of control systems in helping to achieve this balance is of course obvious.
Q5: Lessons learnt – what can we learn from UK and Scandinavia
Interviewer: Finally, what can we learn from building design from either country, Sweden or the UK, when it comes to maximising daylight?
Paul Rogers:
The UK and Scandinavian markets are quite different. While it can be difficult to take something from one region and transplant it to another there are a few ideas which could be worth consideration.
Both regions are under pressure to increase urban density. For the Scandinavian countries, I would like to see a more robust system for dealing with cases where an existing property’s daylight is reduced by new development. I think the Right to Light legislation which is in effect in England and Wales provides an interesting model. I am not sure I will see similar legislation in the Scandinavian counties in my lifetime, but what I do see right now is that in Scandinavia this issue needs to be given a more robust framework for adjudication. On the other side, I think the UK could learn a lot from the requirements for daylight for new construction that you see in Denmark, Sweden, Norway and soon Iceland. I think if there is growth in these areas that it would be beneficial for people living in both markets.
And then with regards to window sizes. It is generally understood that the UK window sizes are smaller than what we normally have in Scandinavia. To improve daylight, it would be easy to say that the UK should increase glass area but it is not that simple. In Scandinavia, energy is relatively cheap when compared to the rest of Europe and in particular compared to the UK. Despite energy being relatively cheap in Scandinavia there has also long been a commitment to invest is buildings which are well insulated and airtight. This has not really been the case the UK. So, while increasing window size may seem a good idea on the surface, there are socio-economic factors need to be taken into consideration.
The UK government recently released a study noting that in the UK, many households have trouble finding the means to keep their homes warm. In this context thermal comfort would seem to be a priority. And then also with larger windows comes the risk of overheating. Prescribing bigger windows may improve daylight yes; but without additional measures to ensure thermal comfort they will not necessarily lead to better buildings.
What I can see in the context of a warming climate is that both markets need to be more aggressive in ensuring that people are protected against extreme heat. This is not to say that people should necessarily accept dim interiors, but rather that there needs to more attention given to balancing daylight and thermal comfort. For both regions, operable solar shading is not only a key strategy to help combat overheating but also one which allows for optimal daylight performance at times when it is most needed.
Tony Olsson:
The Scandinavian perspective today is very much about thinking green - environmentally friendly to reduce negative environmental impacts, while at the same time ensuring that it is an environment that tenants enjoy and feel comfortable in. Clearly a well-designed solar shading and control system has an important role to play here and I think decisions makers are becoming more aware of this.
Conclusion: The discussion between Paul and Tony highlights an emerging consensus. As priorities shift toward building performance and occupant well-being, the path forward points to intelligent systems—dynamic shading, automated controls, and integrated design solutions that balance daylight and energy, without compromising either.
To achieve this balance, we must make decisions about shading early in the design process, not as an add-on but as a core architectural consideration. Solar shading is not just a technical fix. Rather it’s a design opportunity. With the right tools and foresight, we can build spaces that are not only more efficient and comfortable, but more deeply in tune with the needs and well-being of the people who use them.
Looking ahead, the role of solar shading will only become more critical. Climate change is already reshaping our cities and increasing the risk of overheating and this is even true in northern climates. At the same time, the push for higher density urban development calls for smarter, more adaptable daylighting strategies.
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