By Diego Giuliani
Building flexible for a cleaner future. From the Dutch Pavilion at the Osaka Expo 2025 to experimental prototypes in Spain, architects and engineers are rethinking design and construction to foster reuse, and boost circularity. Because “unlike diamonds, buildings are not forever,” they warn. “And constructing traditionally today, means creating tomorrow’s waste”
If you happened to wander through the Osaka 2025 Expo in recent weeks, your gaze surely would have been caught by a futuristic building, with a wavy façade and a dome atop it, illuminated and reflected on its mirror-like roof. From the ground, it resembles a rising sun over water, symbolising what its creators call “A new dawn on common ground”, a confident vision of tomorrow’s world, built on collective problem-solving. “It’s all about using our planet’s renewable and non-renewable resources in a responsible way”, says Sabine Oberhuber, co-author of Material Matters with her husband Thomas Rau, and co-founder of RAU Architects. Specialised in circular construction, their Amsterdam-based firm designed this Dutch Pavilion in Osaka using the same principles: a fully circular building that will be entirely dismantled and rebuilt elsewhere once the Expo ends in October. To make this possible, every element is logged in a materials cadastre, and the steel components of its 1,600-ton structure are marked with QR codes for traceability. “We demolish far too quickly. Instead, we should evaluate what can be reused from existing structures”, adds Oberhuber. “Right now, buildings are often demolished not because they’re unusable, but because they’re depreciated on paper or it’s cheaper to sell the land than to renovate. This creates absurd business models that discourage remodelling.”
Encouraging reuse and remodelling to foster new business models that value circularity is also the aim of a “multipurpose space” currently under development on the outskirts of Barcelona, within the EU project RECONSTRUCT. “It’s a kind of shoebox with a temporary roof, about the size of a shipping container, that will later be dismantled and reconstructed elsewhere for future uses. As a proof of concept, it’s very minimalistic: one floor, one door, no services or insulation – but pillars, beams, façade panels and slabs are all designed to be fully reused or recycled,” explains José Lucas , project manager at the Catalonian Instituton of Construction Technology (ITeC) and technical coordinator of the European consortium. All the materials used are either recovered or developed from recycled content, he adds. “The concrete itself contains no virgin materials and is made entirely from waste – especially olive pits, which we used to obtain a reaction with the blast furnace slag and generate cement, which is the most energy consuming element in the production of concrete. In addition to that, the reinforcement in the façade panels, which are demountable, is all bio-based. We’ll also use recycled aggregates wherever possible. For structural beams and pillars, current legislation limits recycled content to 20%, but we aim to push that to 100%.”
This approach is driven by the urgent need to reduce construction waste. A race against time, accelerated by the world’s growing population and the alarming numbers, recalls Tommaso Giomi, a bioclimatic design expert and colleague of Lucas at ITeC: “Forty percent of the European Union’s waste comes from the construction sector. If you lined up all that waste in trucks, they’d circle the planet ten times. This waste spans the entire lifecycle of buildings: production, construction and end-of-life. And with urban populations projected to reach 80% in some regions by 2050, reusing construction materials is crucial. Adopting circular materials, designed for reuse, is the only way to avoid repeating past mistakes.”
The key word in this approach is flexibility. Given that unlike diamonds, buildings are not forever, making them adaptable to the evolving needs of people and society is paramount. This is what inspired RAU Architects in designing the Triodos Bank offices in Zeist, the Netherlands. Simply assembled with over 160,000 screws, they are entirely demountable, and designed to be rebuilt and repurposed for at least four future lives, as confirmed by recent, independent studies. This same philosophy underpins the prototype developed by Lucas’ team in Spain. “The façade panels will be designed for disassembly, and will be removable to change the shape of the building, he explains. “This allows us to show how both design and product can be reused in different orientations and configurations, and demonstrate the adaptability of the structure. Additionally, the foundation slab will be shaped like a chocolate bar turned upside down, with the segmented part on the bottom. This makes it easy to cut and dismantle selectively, without heavy machinery.”
A further step to make this approach viable, he says, is integrating a digital ecosystem, where material passports, blockchain and life-cycle assessments-including environmental, economic, and social impacts-all help optimize resource use, even when some materials can’t be reused immediately. This very same vision inspired Rau and Oberhuber to create Madaster, an online cadastre of materials and building components launched in 2017 in the Netherlands and now active in seven European countries. “Over time, we’ve added more and more features. Now the platform also shows you the residual material value of cement and other materials, and connects to large data ecosystems like the London Metal Exchange, so you can check the value of steel in your building,” says Oberhuber.
Rethinking the full lifecycle of buildings is also the goal that inspired both the name and the approach of Reconstruct. “From raw material sourcing to end-of-life reuse, we’re reshaping how materials connect and interact from the ground up. We localise and characterise waste in specific regions, link it with industry, and develop new materials accordingly. We’re also developing AI modules that can detect the presence, quantity and type of usable raw materials in construction waste, to keep them from ending up in landfills,” explains Lucas. As futuristic as it may sound, this approach is deeply rooted in centuries-old wisdom which we’ve drifted away from under the illusion of infinite resources. “Think about the Colosseum, whose columns were repurposed across Europe, or the Edo period in Japan, when buildings were routinely dismantled and rebuilt,” says Giomi. “History is full of examples of construction designed for reconstruction. It’s only since the industrial revolution that we’ve lost this mindset.”
Still, shifting the mindset is just one of the many challenges in adopting a circular approach to construction. “The biggest one is regulation around reused materials,” says Lucas. “New products must undergo strict certification and testing. Reused materials don’t yet have a clear pathway to meet these standards. There’s a lot of confusion among public authorities and reluctance among architects who fear regulatory issues.” Another major hurdle is the fragmented nature of the construction supply chain, says his ITeC colleague and Reconstruct project coordinator, Kathleen Blanco: “We work with many stakeholders –designers, architects, manufacturers –and this makes coordination complex. That’s why digitalisation is so important for aligning all these actors within the same framework and ensure a more streamlined process.”
To drive real change across the industry, Oberhuber also suggests integrating circularity into building permit processes and taxing energy and materials more heavily than labour. “Because building traditionally today, means creating tomorrow’s waste”, she concludes.