How the circular economy is revolutionizing construction - key4 by UBS

How the circular economy is revolutionizing construction

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17.08.2022 | 6 minutes

The building sector makes a significant contribution to CO2 emissions in Switzerland. The ideas of “circular construction” or the “circular economy” are mentioned more and more frequently in connection with reducing these emissions. Dr. Peter Richner, Deputy CEO of Empa and head of the renowned research and innovation platform NEST, explains in an interview what lies behind these terms and what opportunities they open up in the building sector.

What is behind the terms “circular construction” and “circular economy”? How does the construction method influence CO2 emissions in the real estate sector?

Peter Richner: When people talk about CO2 emissions in the real estate sector, they usually mean the CO2 emissions caused by heating with oil or gas. It is often forgotten that the production and transport of the material needed for the construction of a building also emit large amounts of CO2. These are referred to as “gray” CO2 emissions. They are often omitted when calculating the energy footprint of a building. Cement is one very well-known example. Producing cement to build a basement or a wall is associated with high CO2 emissions. In our linear economy, the necessary raw materials are procured from nature, processed and disposed of at the end of a property’s life. If we now want to move toward a net-zero society, the use of renewable energies is very important for daily life, but it is equally necessary to compensate for the CO2 emissions that result from the construction of buildings. This is where the circular economy comes into play. In the real estate sector, this refers specifically to circular construction. We do not consider buildings as end products, but as temporary material storage facilities. The material used for the construction of a building is sourced from nature or the existing material cycle, and is also returned to this material cycle at the end of the building’s lifetime so that it can be reused. Particularly in the construction industry, which is the largest material converter in our economy, this can significantly reduce the ecological footprint.

How does returning material to the material cycle and reusing building materials work?

Peter Richner: In general, there are four options. Of course, it is best to choose construction methods from the outset that will allow buildings to be used for as long as possible. This begins with planning and design. When a building is designed so that the individual components can be used for as long and as flexibly as possible, this maximizes longevity.
A second possibility is “reuse”, i.e. using individual components for a new purpose. For example, if a door is no longer needed in one building, it can be used in another. However, hardly any buildings in Switzerland have been built in a way that allows deconstruction, i.e. the dismantling of a building into its individual parts. At the end of a building’s life, demolition remains the most common option.
The third option is “recycling”, i.e. the refurbishment and reuse of individual building components. The most advanced area here is concrete. In Switzerland in particular, the use of recycled concrete is well established – especially when constructing buildings. For this purpose, demolished concrete properties are transformed back into aggregates. Mixed with fresh cement, the substance can then be used as new concrete.
A fourth option is to upgrade existing components. Windows are a good example of this. Of course, the ideal solution would be to simply reinstall a window removed from a building in a new location. However, especially in the case of windows, which have undergone major developments in terms of energy in recent years, the question often arises as to whether this makes any sense at all. In such cases, an old window can be upgraded by adding additional glazing or replacing the insulating gas between the panes relatively inexpensively and with quite a small amount of new material.

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“Net zero” is on everyone’s lips. Is it really possible to build a “net zero” house through circular construction?

Peter Richner: The life cycle of a building begins with its construction and ends with its dismantling. Net zero is achieved when, over its entire life cycle, the building does not change the CO2 concentration in the atmosphere. However, certain processes will always involve CO2 emissions. Consequently, other processes must recover CO2 from the atmosphere in order to achieve net zero. One option here is building with wood. However, in order to compensate for wood combustion, which is also associated with CO2 emissions, the wood must circulate in the material’s life cycle for about 100 years.

Another option is the pyrolysis of biogenic materials. In this process, the carbon that plants have obtained from the air via photosynthesis is recovered as a solid and can in turn be used as an additive in concrete, as insulation material or even in road construction. Applications in the construction industry are particularly suitable because very large quantities of material are converted and a corresponding reduction effect can be achieved.

Besides wood, which materials do you think have the most potential?

Peter Richner: Almost all materials have the potential to become part of the material cycle. The connection technology is a key element. As soon as something is glued or welded, you have a problem, unless you can reuse the component as a whole. In the cycle context, “screwing” and “joining” are used as joining techniques. This was exemplified in the UMAR unit we built at Empa’s NEST. In the two bathrooms, there are no silicone joints or any glued or welded components, and the whole unit could be disassembled into reusable parts by two people with a cordless screwdriver at any time. And this is exactly the point of circular construction: everything has to be built in such a way that it can be taken apart again, and it has to be documented in such a way that in 30 or 40 years’ time, you will still know which building elements are part of the building in order to be able to continue planning with them. If you think of buildings as temporary material stores, you also need a good inventory for each building. Without an inventory, a warehouse is useless. Digitization tools, which are now becoming more and more widespread in the construction industry as well, help to simplify the documentation of these processes.

About Dr. Peter Richner

As Deputy CEO of Empa, Dr. Peter Richner is responsible for the research strategy in the energy sector and heads the “Engineering Sciences” department. His research is centered on reducing the ecological footprint of a building stock. From 2014 to 2016, he headed the Swiss Competence Center for Energy Research (SCCER). In addition, Dr. Peter Richner is in charge of NEST, a unique research and innovation platform that promotes the development and validation of new solutions for buildings in real conditions.

Since June 2020, Mr. Richner has hosted the monthly podcast “NEST Podcast: The Future of Construction”, in which he discusses current topics relating to the construction sector with guests from industry, science and politics.

You explained that sustainability in construction plays a role as early as the planning stage. Does that mean that circular construction starts with the design?

Peter Richner: Exactly, circular construction is not just a big research topic, it is actually also a crucial aspect for planners and designers or even architects. There are certain areas, such as timber construction, where research projects are required to find out how to optimize the flow of forces in large structures despite the use of other joining techniques. But in many fields, this type of research is not necessary. The main thing that is needed is creativity. The planning is currently perhaps a little more complex, because owners and tenants are not yet accustomed to these new concepts. And suitable business models are often not yet available. Imagine that you are building a house. In keeping with the spirit of the circular economy, it would be best not to buy new windows, but to rent them from the manufacturer. If the house ever has to be demolished, the company in question could then remove the windows and put them back into another building. Many people still cannot imagine anything like that today. But this creates completely new business opportunities and services that would not be possible without circular construction.

What is the current status of the circular economy in the construction industry in Switzerland?

Peter Richner: In Switzerland, there are some pioneers in the field of the circular economy who are strongly driving this development. It is also clear that there is a great deal of interest in the subject. However, although there are various component exchanges, the market for reused materials is still limited and components are only available in small quantities. The problem is that if we want to close the loop, there needs to be a reasonable amount of material to use. In construction, we often have the problem that the accumulation of these materials is quite scattered and we simply do not have enough of them available. For example, it is difficult to equip an apartment block with 40 identical windows. Since the accessibility and availability of material are not yet very good, finding the necessary material is very time-consuming and cost-intensive. In my opinion, this is currently the biggest challenge.

You are responsible for NEST, Empa’s research, demonstration and innovation platform that allows research to be carried out and new solutions to be developed in and on a real building. What sets NEST apart?

Peter Richner: NEST is a place where research and industry come together and objects can be scaled up from lab scale to real scale to test whether everything works as hoped in reality. The leap of scaling up is always associated with great risks. At NEST, we can conduct tests in a safe setting. However, people also work and live in the NEST units, which involves putting the systems we have developed to the test.

Switzerland has a very strong research scene and we have a large construction industry. But the speed of innovation is, in my opinion, far too slow for the major challenges we are confronted with. It is precisely when faced with this acceleration of the pace of innovation that NEST can play an important role.

There is even a NEST podcast that you host, which airs every month. What topics do you address in this podcast?

Peter Richner: The podcast is called “NEST Podcast: The Future of Construction” and it revolves around innovation in our sector. One of the more recent episodes was recorded with Empa researcher Mirko Kovac, who is studying the role of aerial drones in the construction, maintenance and operation of buildings.

Otherwise, the podcast often evokes the reasons why we are making such slow progress in the circular economy. And why there could soon be a turnaround, for very unfortunate reasons. Suddenly, everyone is thinking about how to get by without Russian gas and oil. Unfortunately, changes can only be made very slowly in the real estate sector. At NEST, we have developed various solutions over the last few years that are now ready for practical application. However, the problem is that there are not enough of the craftsmen and planners required to ensure a rapid transition. But I very much hope that a change will take place in society.


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