The technology is based on using materials and colors that reflect sunlight and emits thermal infrared radiation in a wavelength range that allows the heat to be dissipated through the atmosphere and out into the cold space. It is particularly effective in areas with a lot of sunlight and little cloudiness, such as deserts, where low temperatures can be achieved even in the middle of the day.

"The technology is particularly attractive in warmer countries, but even in Sweden we have problems with phenomena such as the heat island effect, which makes cities warm. Replacing black roofs with white ones can be one way to counteract that", says Anne Andersson, researcher at RISE, and continues:

"We also receive many enquiries from Swedish companies that are interested in developing their materials with these properties in mind."

Cools its surroundings

When two objects of different temperatures come into contact, heat is transferred between them. The hotter object gets colder, and the colder object gets hotter. In this way, buildings can be cooled when, for example, the roof gets colder. The effect can be observed on some mornings when frost forms on the car's windscreen, even if it is not freezing, when the surface has become colder than the surroundings. The more sunlight that is reflected and heat that is emitted, the more the material can cool its surroundings. Through measurements, a solar reflective index can be determined to quantify the effect of different materials and colors.

"All colors and materials reflect, but some more than others. White color that reflects a lot of sunlight and at the same time allows heat to be emitted is the best choice. At the same time, the material and color need to work for the building from other aspects as well, therefore it is important to characterize different materials to find the most optimal solutions", says Anne Andersson.

European project develops the measurements

Homes, office buildings, industries, shopping centers and data centers can all benefit from the technology as a cost-effective cooling system. And even the cooling effect only results in a few degrees colder, it can be an important piece of the puzzle to help combat climate change. However, despite the obvious advantages, there is still a lack of methods to evaluate and compare the performance of different materials and colors under real conditions. Anne Andersson participates in the European research project PaRaMetriC (Metrological framework for passive radiative cooling technologies), where she performs and develops measurements on these materials and colors.

"This is nothing new, it is no coincidence that buildings are white in warmer countries. But to develop the technology and be able to choose the most optimal materials and colors, we need methods to compare, which requires us to develop reliable measurements", says Anne Andersson.

In its Circular Economy Action Plan, the EU aims to double the share of recycled materials used in the Union between 2020 and 2030. The stated aim is to reduce the extraction of so-called virgin materials and the production of new raw materials. But, so far, the transition is slow, not least because of low acceptance among end consumers, gaps in technology and system development, and uncertainty linked to recycled raw materials. 

Low pace of transition stems from uncertainty 

In 2021, the proportion of recycled material corresponded to 11.7% of the materials used in the EU, an increase of only 1% since 2010. 

“Several companies are not ready to take decisions that would have a real impact,” says Peter Stigson, Research and Business Developer at RISE. 

There are many reasons for this, including uncertainty about traceability and quality, as well as long-term availability. 

“It’s true that there is a lot of variation in the availability of recycled products right now,” says Jönsson. “But remember, in the long run, the opposite is true: access to virgin material will be similar to the situation with oil. Other raw materials, such as cotton, which requires an unreasonable amount of water and area to cultivate, are becoming increasingly problematic. In other cases, we will have a type of material competition. For example, what should we use Swedish forests for? Clothes, paper, house, energy...? We will not be able to do everything, but must find ways to instead recycle and reuse what is what we can.” 

One example is the critical metals and minerals that will be needed in the energy transition. Here, RISE has carried assessments on the long-term availability: 

“These must also enter the recycling cycle. Less than one percent is recycled today.” 

Traceability challenging but important 

And equally important is our common approach to recycling. Peter Stigson has headed up expert groups with a focus on increased traceability and circular economy from a system perspective. An interesting question was how the sometimes problematic history of the original material should be viewed. Take cobalt as an example, which may have been mined in a reprehensible way, many people feel that it should be recycled since it is already in circulation. But can recycling really erase a sense of guilt? And how should the history of a material be communicated? 

“Our group of experts concluded that you can’t just ignore the origin of a material – it must be regulated and communicated in some way. But this is complex, particularly when it comes to metals that are melted down and mixed time after time. The way the issue of responsibility and information should be viewed is more akin to philosophy, ethics, and morality. The important thing is that everyone, not least consumers, understands the problem and accepts the solution.” 

Christina Jönsson: 

“A circular economy requires trade-offs, for example, when it comes to the properties and sometimes even the quality of recycled materials.” 

Customers must accept new ways of thinking 

A clear example is the concept of mass balance, which means that companies mix a certain amount of recycled material into a production run. This means that individual products, such as a bag, may not contain the amount of recycled material claimed by the company, but the series itself does over time. 

“This is a concept that some find difficult to accept,” says Stigson. “If someone buys a backpack that is stated to consist of 50 percent recycled, the person expects that particular bag to contain that percentage. But on a larger scale, it doesn’t work that way, and if the major manufacturers are to accept recycled material, they need to be able to set targets over time.” 

Long list of policies now becoming regulations 

A lot of changes will be noticeable in the future. On the one hand, numerous policies at both EU level and international level have now been adopted and have started to trickle down as regulations. 

“But we are also starting to reach a point where we are achieving both a technical and regulatory level and becoming more willing to make investments,” says Jönsson. “There has previously been a lack of technologies, operators, traceability systems, logistics systems... Now, politics is also pushing us in that direction and processes and technology are starting to become more commonplace.”

When Gävle was hit by torrential rain and severe flooding in the summer of 2021, the costs of the damage were enormous. Insurance companies paid out over one billion kronor in claims linked to the incident. The effects of climate change are becoming increasingly tangible. Incidents like this underscore the work that needs to be done to transition and adapt our societies to a changing climate. 

“It’s getting serious now,” says Niklas Thidevall, policy researcher at RISE, who conceived the climate resilience certificate system. “We saw in Gävle how a single downpour could have enormous consequences, and this is something that individual property owners, private individuals, and companies that own properties will have to deal with.” 

Risk for both insurance companies and banks 

Insurance companies warn that properties in risk zones may not be able to get the same cover as before, which also creates problems for banks and other entities who lend money with real property as collateral.  

“We are now facing a situation where some properties can be difficult to insure and thus difficult to finance, which creates major challenges,” explains Thidevall. “At the same time, it is currently very difficult for banks to know what risks they are taking.”  

Thidevall highlights two things that became clear with the floods in 2021. Firstly, there is a big difference in how different properties are affected, even in the same area. Secondly, much of the damage could have been mitigated and the risks reduced using relatively simple solutions. A large proportion of the damage in Gävle was linked back to back pressure damage, where wastewater is pushed back into the house, and cold have been avoided with relatively simple means, such as installing a check valve. 

Model for assessing risks 

To increase the resilience of existing buildings, it is important to know more precisely which property has a high risk of being affected, and requirements for predicting and reporting risks will most likely increase in the future. Therefore, a model for assessing the risks of damage related to climate change at the property level has been developed in a feasibility study.  

“We have mainly looked at the risk of flooding, both due to torrential rain and rising sea levels, and sketched out the form such a system could take,” says Thidevall. “We started from an existing example, namely the energy performance certificate that each property has. We have the same scale, although it measures how vulnerable the property is to climate-related risks.”  

The scale is based on assessments from independent experts who collect data and place the property on the scale according to various factors, such as the design of the building foundation, the ground around it, how thresholds are designed, whether there is a forest close to the property or whether there are basements and, if so, whether they are furnished, and so on.  

“You look at both the building itself and the risk of incidents on-site,” says Peter Lidén, researcher in Indoor Environment and Building Physics at RISE. “Taken together, these data result in a risk rating. In the next step, a private individual can, for example, get recommendations for what can be done to achieve a better rating on the scale, such as altering the surrounding ground levels, or inspecting the seals between different building sections where water can penetrate. Owners of multiple properties can produce documentation for assessing which of their properties they should secure first.” 

Creating incentives – and change 

The idea is that the information will be mandatory for new property development, but it is likely that it will also be requested for existing buildings. However, it is not about condemning vulnerable buildings; the system is a tool to solve problems, help property owners comply with the requirements, and, ultimately, achieve actual change and less damage.  

“Small changes often make a big difference,” says Thidevall. “But if we don’t create opportunities for individual property owners to understand the risks that exist, I don’t think that the measures needed to withstand a downpour or a forest fire will be implemented.”  

The scientific community agrees that the weather will become more extreme in the future, with higher sea levels and torrential rain occurring more frequently. It will cost money to implement measures, but it will also cost a lot if we do nothing.

RISE serves as a meeting place and arena for discussions, projects, and feasibility studies of this nature. 

“You can utilise the extensive expertise within RISE, in this case construction experts and rainfall climatology experts, together with people like me who know the regulations and policy work. Bringing together areas of knowledge, looking at the problem together, and having close dialogue with a wide range of operators provide different perspectives, which produce better solutions.” 

There is a shortage of housing in many parts of Sweden, while many office buildings stand empty. To tackle this problem without having to demolish and build new premises, we need to get better at renovating those that already exist. If existing city buildings can be used for new housing – and also furnished with recycled material – new homes can be created with a fraction of the climate impact of new developments. This is one of the challenges being addressed by the research school ASSURE, which stands for Adaptation of urban Space through SUstainable Regeneration.

Greater use of existing materials 

With the help of eight doctoral students, the school will spend five years looking at, among other things, how to prevent segregation and gentrification when renovating and transforming, how to become better at taking advantage of cultural heritage values in renovations, and how to reuse existing materials to a greater extent.  

To get all the pieces in place, doctoral students from various disciplines are needed, along with a practice-based and interdisciplinary approach.  

 “It’s important to include both those who work with ventilation installation and those who work with cultural heritage matters,” says Magnus Johansson, researcher in urban development at RISE and coordinator of the project. “When you have different backgrounds and twist and turn things together, you will ultimately understand each other better.” 

Johansson also says that to develop usable methods and approaches that work and benefit society, the research must be practice-based. A network has therefore been established comprising companies, architects, the National Board of Housing, Building and Planning, and the Swedish National Heritage Board. 

Dialogue produces real and relevant solutions 

Every spring and autumn, ASSURE will also hold a conference to discuss the school’s progress and direction. 

“Through the network and the recurring conferences, we will have continuous dialogue with the business community and interns, which we believe is the best way to develop a solution that is not a desktop product but that provides real and relevant solutions,” explains Johansson. “We want to engage in discussion that leads to learning.  

The goal is for everyone who works with renovation issues to receive support to do so in a better way and from a broader perspective – but based on local conditions and different needs. 

“We want to increase awareness and understanding of how to renovate sustainably so that different operators can pick and choose the things they need. The research school becomes like a smorgasbord of new thoughts and ideas, individual companies can pick the tools or perspectives they need in a specific situation.”  

Important bridge between academia and industry 

RISE is the coordinator of the project and serves as an important bridge between academia and industry.  

“This is exactly what RISE does: solve societal challenges and contribute to innovation in a competitive way. We help to develop new knowledge and then ensure that it reaches society. The research school encompasses all of these aspects.”