[Images courtesy of Chalmers University]
The circular economy is often discussed at the scale of individual buildings, but real change depends on understanding the built environment as a system. During a recent visit to Chalmers University of Technology in Gothenburg, BUILD met with Maud Lanau, whose research focuses on material stocks, data, and circularity in the built environment. In this conversation, Lanau explains why better data is essential for circular design and how constraints can become a powerful driver of architectural creativity.
Tell me about your background.
I originally studied applied physics at the Université Paul Sabatier in France, followed by the first year of a master’s degree in building engineering. During this master’s program, I realized that I did not really want to work in an engineering firm, so I moved to Chalmers to study industrial ecology. Industrial ecology is about understanding society as an interconnected system and identifying where sustainability improvements can be made. You gain knowledge and skills in sustainability assessment, the circular economy, and systems analysis. Eventually, I applied these concepts to the built environment during my PhD in Denmark and my postdoc in the UK. Now back at Chalmers, I am still focusing on the built environment, which is why I work so closely with architects today, even though I’m not an architect myself.
Was there a moment when you knew you wanted to apply your expertise to the architectural world?
I’ve always been interested in buildings and cities, and more generally in how humans shape their surroundings to improve their living conditions. In industrial ecology, you eventually focus on a sector—textiles, automotive, or the built environment—and I usually chose my course projects on construction-relevant topics… This was partly because I had some knowledge of building engineering, but also because my studies emphasized how impactful the built environment is in terms of resources and emissions. Working in this field felt both meaningful and necessary.
Do you have a secret coping mechanism for tolerating us architects?
It’s been fine, honestly. Many of my friends are architects, and I think I understand their mindset. But from what I know, being an architect in Sweden differs from being one in France. In France, architects have a more formal status—they cover both artistic design and can legally sign plans. In Sweden, architects can’t do that without certain engineering certifications. I am not sure if this is why conversations here feel more flexible, or if it is simply because I mostly work with architects who already care about sustainability, which probably gives me a biased but pleasant experience.
You are known in Sweden’s academic world as an expert in the “data of the circular economy.” What does that mean in practice?
My main work is modeling the built environment in terms of material stocks—what materials we currently have embedded in buildings. Once we know that, we can prepare for circularity at scale. Looking at one building at a time isn’t enough; we need to understand what exists at the city and national levels. How much material is already available, and where? How much new material do we still need? With accurate stock data, we can support architects, municipalities, and construction actors in planning for circularity, including reuse and recycling.
What does the modeling process look like?
The basic modeling level relies on building archetypes. For example: a 1940s terraced house in Sweden. We examine archival building plans that fit this archetype, identify materials, and quantify them per square meter. Because we know where these buildings exist across the country, we can scale those quantities up. That gives us a rough picture. But averages bring uncertainty: you may know the total amount of glass in a region, but not the exact size of every window. Even so, architects tell me that even rough data is helpful—knowing that clay bricks will soon enter the reuse stream allows them to design accordingly.
So you’re effectively building a picture of future material availability?
Exactly—trying to understand what the pipeline could be. But it’s challenging. You need to know: what exists, where, when it will be available, and in what quality. Without those four components, it’s hard to inform design. To improve accuracy and add details to the basic modeling, we use digital tools and techniques—Google Street View, for example. A human can identify brick vs. concrete, but one cannot walk around an entire city and write down this information for each building; now, we train algorithms to do that at scale. With machine learning, AI can help detect material types, roof tiles, window dimensions, and so on. But this only works with what is visible: the material inside a wall is still very difficult to identify—stucco hides everything.
How far along is the field in assessing the condition of materials—especially damage during deconstruction?
That’s an active area of research. First, we need to know whether the material was ever in good condition to begin with. Some of that is inferable—insulation from the 1930s may contain asbestos; insulation from the 2000s should not, according to regulation. But true quality assessment must happen on-site. Other quality issues, such as whether structural elements can be reused, are more difficult to infer at scale. In our field of material stock and flow analysis, we focus on quantifying and locating materials; other fields specialize in condition, testing, and certification.
Do your studies focus on Sweden specifically? Or is your dataset broader?
When conducting this type of study, one typically focuses on the local built environment, since it is easier to access local data as well as local construction knowledge. Therefore, my PhD was in Denmark; my postdoc focused on the UK, and now I’m mostly studying Sweden. But I also collaborate with colleagues working on China, Japan, North America, and several European countries. Material stock research is global.
Where are the “hotspots”—places with the most potential to harvest reusable material?
Hotspots usually emerge where cities are developing rapidly and are demolishing frequently. But from a sustainability standpoint, that’s not good news. Ideally, buildings would last as long as possible. Rapid demolition increases outflow—but it also signals unsustainable turnover.
I recently spoke with Walter Unterrainer about transforming cities rather than demolishing them. How does harvesting materials fit into that?
That’s more of an architectural question, but I’d say this: a new architectural language is emerging—one that embraces circularity, visible reuse, and materials that don’t necessarily look “new.” Some communities find that exciting; others less so. In my department, we’re working to integrate these topics into architectural education, because engaging with circularity is becoming essential for future architects.
How do you integrate your expertise into your teaching?
I ask students to do a miniature version of my work—quantifying materials in a few buildings from the 1940s, for example. They need to understand how stock data is created, what uncertainties exist, and how to interpret it critically. If they assume data is perfect, they’ll use it incorrectly. More broadly, all education from our research area (Sustainable Built Environments) emphasizes systems thinking. The built environment is part of larger systems; improving a building doesn’t necessarily improve the system. We incorporate life-cycle and systems thinking, multidisciplinary teamwork, and project-based learning.
Do students take this knowledge into their design studios?
I believe so, though I don’t directly track their studio work. Many students carry sustainability themes into their master’s theses. And I teach students from several programs—construction management, infrastructure, environmental studies… and I even had a student in real estate business recently.
A lot of experts I’ve spoken with say policy and politics are lagging behind circularity efforts. What do you think needs to happen next?
For my work—data—the first task is aligning statistics. There’s a lot of data that exists but is inaccessible or inconsistent. At a societal or political level, I would say that Sweden is doing relatively well – at least that is what I take from my conversations with my international colleagues. For example, Gothenburg has ambitious net-zero construction targets, and many actors are engaged. I see the bigger challenges – not specific to Sweden, but rather typical of the construction industry – as industry inertia and siloed communication. For example, waste managers and designers need to collaborate. Clients must be willing to embrace reuse. There is also a skills gap; it’s important that practitioners can access reskilling opportunities. Economic incentives will help, but I’m not a policy expert.
Several companies in Northern Europe are developing models for deconstruction and material storage—firms like Lendager in Denmark, Rotor in Belgium, and Lagemaat in the Netherlands. Is your research connected with any of them?
Yes, and these firms are essential for scaling circularity. One of my PhD students is studying where logistics hubs should be located so that storage and distribution are efficient in terms of both logistics and related environmental impacts. He interviews these companies to understand real-world needs—space requirements, workable distances, and on-site workflows. Their field knowledge complements our modeling. Increasingly, my students collaborate with these firms, and that dialogue helps ground their research in the realities of practice.
Two terms came up in my research of your work: “digital twins” and “material passports.” Can you define them?
Digital twins are digital replicas of cities. Assuming you have information on your city—energy consumption, noise levels, air quality—you can layer them in the same place. For research, it helps us study interactions between systems. But it also helps engage decision-makers and citizens, for example by showing the results of various urban planning decisions. In the context of digital twins, my research is about making sure the material resource layer is included in the model of the city. Then, there are material passports, which summarize key information about a building: they detail the quantity, location, and size of materials. Ideally, every building would have one.
So the ideal scenario is that every city has a digital twin, every building has a passport, and all data is integrated?
Yes. In that scenario, many new business models could emerge—if the data were open. But open data raises security concerns; detailed building information can be sensitive, and we need to determine what data is safe to share. But we have to be practical: getting detailed data for all new buildings is doable and that’d be a great step forward. For older buildings, the information is still patchy, but that’s okay — as long as we make sure the information in digital twins is accompanied by uncertainty indicators. That way, decision-makers know exactly what’s solid and what might be less reliable.
Is data sensitivity and data handling part of what you teach?
To build these models, we combine satellite data, street-level imagery, building archives, BIM files (Building Information Modeling), and more. Students need to understand which data is important, what’s feasible to collect, and how to handle all of it responsibly.
Do you work directly with building departments or jurisdictions?
Absolutely. We collaborate heavily with Framtiden, a municipality-owned umbrella organization that owns about a quarter of Gothenburg’s apartments. They’re also tasked with advancing the city’s circularity goals, and we have been closely collaborating in recent years. They are very interested in the stock modeling of Gothenburg, and they’ve been very supportive, especially when it comes to communicating with practitioners and getting their feedback.
From an aesthetic perspective, do you see students beginning to think differently about design?
I don’t teach enough architecture students to generalize, but in exhibitions and projects I see increasing interest in showing reused materials proudly—valuing their history rather than hiding it. How much that translates into built work, I’m not sure.
Can availability begin to dictate design too much? Is that a concern?
Some architects worry about excessive constraints. I understand the concern, but I believe constraints can drive creativity. My bias is that we should work with what we have. Limited resources can spark new ideas. In my work, we use the phrase: “form follows availability.”
Why do you think the practical, on-site side of construction is evolving so slowly?
The entire construction industry is structured around linearity. BIM models assume standardized, readily available materials. The design process assumes predictable deliveries. Reuse disrupts the “what” and the “when.” Suddenly materials are unique and arrival times are uncertain. Inventory systems don’t yet exist. In my view, organizational change—not high-tech innovation—is the biggest obstacle.
Where are the biggest failure modes for circularity?
It depends on the scale. For citywide circularity, communication between companies is critical. If circularity happens only within individual companies, opportunities shrink dramatically. A broader, open system is necessary. And this system would very likely call for storage infrastructure—materials need somewhere to go between deconstruction and reuse. Quality assessment is another challenge.
What is your elevator pitch to countries behind in the circular economy mindset?
I’d say: We are heading in the wrong direction, and the built environment is a major part of the problem. Reusing materials is one of the most effective ways to decarbonize and reduce resource use. But it requires effort, coordination, and new systems. The sooner we begin, the better—and the alternative is simply not sustainable.
Are there projects you’re particularly excited about?
Many small-scale projects are happening, but I tend to stay focused on system-level research—city and national scales. I’m waiting to see which approaches solidify and become part of long-term practice.
How do you think about the boundaries between academic inquiry and real-world application?
Dissemination is part of my job, but it brings questions: When am I a researcher? A consultant? An activist? We talk about this often at Chalmers. When I worked in the UK, we convinced architects to share data by offering them a circularity analysis in return. Often, they were very keen on better understanding circularity concepts: circularity is a hot topic, but they were also overwhelmed by the amount of seemingly contradictory information. For others, conversations were simply about the fact that older bricks are far more reusable than concrete. Those conversations are rewarding. In any case, the part of my research we are talking about today centers on supporting circularity in the construction industry. So, it is intended for real-world application. But there’s another facet to my work that’s more theoretical: using stock modeling to explore how societies consume, store, and discard resources over time. This perspective is known as socioeconomic metabolism — it’s like viewing society as an organism, inherently dependent on resource flows and stocks to maintain itself and grow. The real challenge is how it can do so within planetary boundaries. Fascinating, but perhaps less directly actionable for practitioners.
Does your work consider the monetary value of this data?
Not directly. My work is owned by Chalmers and is meant to be open. We developed a visualization tool in the EU project CREATE and discussed turning it into a private spin-off, but our preference is open research. Still, there’s clearly business potential for others.
Any final words?
Only that the built environment holds extraordinary potential for more resource efficiency and circularity—but realizing it requires rethinking systems, expectations, and aesthetics. And that work is only just beginning.
Which three books would you like to see on the bookshelf of every architect?
In my scientific field, we work mostly with scientific papers, so I will give you three papers instead!
The economics of the coming spaceship earth, by Kenneth Boulding (1966).
Back in the 1970s, this US economist framed Earth as a spaceship with limited resources, calling for a “spaceship economy” instead of the “cowboy economy” that assumes endless abundance. The whole piece really captures the two contrasting views… it was written decades ago but it is more relevant than ever in today’s environmental debates.
Full reference: Boulding, Kenneth E. “The economics of the coming spaceship earth.” In Environmental quality in a growing economy, in Jarrett (ed.), 1966. Environmental Quality in a Growing Economy, pp. 3-14. Baltimore, MD: Resources for the Future/Johns Hopkins University Press.
Conceptualizing the built environment as a social–ecological system, by Sebastian Moffatt and Niklaus Kohler (2008).
This is a great read for those who wonder what “looking at the built environment from a systems perspective” means. The authors explain everything clearly and their work is still extremely relevant today.
Full reference: Moffatt, Sebastian, and Niklaus Kohler. “Conceptualizing the built environment as a social–ecological system.” Building research & information 36, no. 3 (2008): 248-268.
The weight of society over time and space, by Hiroki Tanikawa and colleagues (2015).
The first account of material stocks at the country level, accounting for all construction materials in all buildings and infrastructure, above and below ground. The 3D mapping of the total material quantities across Japan is really efficient in showing how resource-intensive the built environment is.
Full reference: Tanikawa, Hiroki, Tomer Fishman, Keijiro Okuoka, and Kenji Sugimoto. “The weight of society over time and space: A comprehensive account of the construction material stock of Japan, 1945–2010.” Journal of Industrial Ecology 19, no. 5 (2015): 778-791.
Dr. Maud Lanau is Assistant Professor at Chalmers University of Technology (Sweden), in the research group of Sustainable Built Environments. Her research focuses on reducing the environmental impacts of the built environment while ensuring that it continues to support essential services for human well-being.
Using systems thinking and the concept of socioeconomic metabolism, Dr. Lanau examines how we, as societies, consume resources and generate waste to sustain themselves and develop their built environments. A key part of her work involves mapping the construction materials used for, stocked within, and discarded from the built environment. Such models result in resource cadasters that she analyzes from different angles through collaboration with experts from various fields, including urban morphology, construction management, geotechnics, and governance.
By better understanding the patterns and drivers behind our use and accumulation of construction materials, Dr. Lanau seeks to identify points of intervention to support the construction sector in moving towards more sustainable practices.