Barcelona is the first city in the history of the UIA World Congress of Architects to host the event twice. The 1996 edition, Present and Futures: Architecture in Cities, arrived at a charged moment, when the post-Olympic city was consolidating an urban model that would become one of the most studied and contested in contemporary urbanism, and when architecture was learning to think through the large metropolis as its primary site of inquiry. Thirty years later, the same city reopens the question under a different condition: one in which the built environment can no longer be understood as a self-contained object, but only through the wider ecological, material, and political systems that sustain it. The theme of the 2026 Congress — Becoming. Architectures for a Planet in Transition — does not abandon the urban concerns of 1996; it reopens them from a planetary scale.
The curatorial team behind this edition, formed by Pau Bajet, Maria Giramé, Mariona Benedito, Tomeu Ramis, Pau Sarquella, and Carmen Torres, approaches architecture as a critical and transformative tool rooted in territory, working across practice, research, and teaching. Their program structures the Congress around six interconnected thematic lines (Becoming More-than-human, Becoming Circular, Becoming Embodied, Becoming Interdependent, Becoming Hyper-Conscious, and Becoming Attuned) and distributes it across three venues of very different characters — Les Tres Xemeneies del Besòs, the Disseny Hub at Glòries, and the CCIB — each chosen for what it represents as much as for what it can hold.
With forty-eight psychogeriatric beds and sixty-eight wheelchair-accessible apartments, accommodation for informal caregivers, and space for bedside care, the De Keyzer building opened in Amsterdam in 2011. Its program had been conceived entirely for elderly people requiring assistance, but shortly after completion, the building was sold to an investment fund, and the apartments began to be rented to young families with children.
For the project's architects, Tom Frantzen and Karel van Eijken, the episode could have been interpreted as a failure of prediction. Instead, it became a confirmation. "It showed, very clearly, that buildings can end up being used in completely different ways than originally intended," Frantzen recalls. The transformation was only possible because the apartments were generous and because the structure allowed for uses more diverse than those anticipated in the original program. Had the building been designed solely for its initial function, the change of use would likely have required a destructive renovation or, in the extreme, demolition.
From acoustic and thermal cladding systems to masonry units and textiles made from agricultural waste, experimentation with bio-based materials continues to drive sustainable solutions for the construction industry. Faced with the urgent need to rethink how we conceive of and interact with the materials that shape the built environment, professionals, researchers, and educators are addressing different design scales and project phases, recognizing the importance of reducing carbon emissions and the industry's environmental impact. In partnership with Bagaceira Project, the Sugarcrete® acoustic and thermal panel prototype, developed by the University of East London (UEL), demonstrates how low-carbon design can transform agricultural waste into high-performance building materials.
The construction industry today faces an unavoidable paradox: the urgent need for sustainable solutions for the future of cities collides with the exhaustion of the term "sustainability" itself, often reduced to a hollow commercial label. In this scenario, Arquivo – one of the winners of ArchDaily's 2025 Next Practices Award – emerges as a facilitator and mediator between different stakeholders in the construction field through disassembly – or rather, de-construction – and the reuse of building elements. Etymologically, if "construction" derives from the Latin construere (to heap up, assemble), the prefix "de-" imposes a conceptual inversion: it is not about destroying, but about disassembling with intelligence to understand the logic of the parts.
In the nineteenth century, entire railway networks became obsolete almost overnight, not due to physical deterioration, but because of changes in the technical standards that supported them. The expansion of railroads across Europe and North America adopted different track gauges (the transverse distance between rails), and as a dominant standard gradually emerged, these infrastructures became incompatible with one another. This required large-scale adaptations, conversions, or even complete reconstruction, in what became known as the "Gauge War."
With the mass adoption of telecommunications networks in the twentieth century, cities around the world built large telephone exchange buildings filled with electromechanical equipment responsible for routing calls between regions. These structures were highly specialized pieces of infrastructure, often occupying entire city blocks and organized around large-scale technical machinery. With the transition to digital switching technologies and, later, the widespread adoption of mobile telephony, much of this equipment became obsolete within a few decades. The buildings themselves often remained structurally sound, but the systems they were designed to support had already evolved beyond them.
How heavy is a house? In his 1965 essay A Home Is Not a House, Reyner Banham observed that modern American dwellings were becoming structurally lighter while growing heavier in mechanical services, such as plumbing, wiring, heating, and cooling. The true weight of architecture, he argued, was no longer in walls and roofs, but in the energy-intensive systems that sustained comfort.
Decades later, the question was updated at the 7th Lisbon Architecture Triennale. Curators Ann-Sofi Rönnskog and John Palmesino asked: How heavy is a city? The scale shifted from the domestic interior to the territory. The technosphere, materialized in the estimated 30 trillion tons of human-made matter on Earth, reframes the discussion entirely. Cities, data centers, oil fields, logistics hubs, satellites, cables, and waste streams form a planetary system in which architecture is neither object nor backdrop, but participant.
Exhibitions can be an opportunity to extend architectural discourse beyond professional circles, opening conversations with broader publics and serving as an interface between architecture and society. Within this concept, major international events such as the Osaka International Expo 2025 and the Venice Architecture Biennale have adopted the idea of the circular economy as one of their organizational objectives. The idea of circularity in events can be reflected in, for example, their energy consumption, the impact of the displacement they generate, their waste, or the useful life of their infrastructure. The site destined for the last World Expo, held in Osaka from 13 April to 13 October 2025, was surrounded by a massive timber structure designed by Sou Fujimoto Architects, one of the world's largest wooden constructions. The Japan Association for the 2025 World Exposition committed to reusing building materials "as much as possible," with concrete plans for their reuse to be finalized by March. In the meantime, some relocation alternatives are already emerging for the pieces of the World Expo structure.
The circular economy, including the reuse of building materials, is fast becoming a key component in the fight against carbon emissions. This involves designing to minimize waste and utilize materials that can be reused at the end of the building's life. On the opposing side, the reuse of materials from partially or wholly demolished buildings can also reduce waste and carbon emissions that would have resulted from using virgin materials. Sustainability purposes aside, the reuse of building materials has a centuries-old history, both for symbolic reasons and simply out of necessity.
Which materials have taken center stage in the architectural discourse of 2025? Which projects have rediscovered new construction practices and methods through material innovation? While the future of building materials still appears uncertain, year after year, experimentation and research continue to reveal diverse practices, initiatives, and efforts dedicated to understanding their value and responsibility within the built environment. From agricultural waste that reduces carbon footprints to recycled plastics given new life, and living materials that engage with emerging technologies while reconnecting with nature, 2025 has highlighted and strengthened the role of architects as mediators between materials, disciplines, knowledge, and interests from diverse origins.
Bolete Lounge BIO®. Image Courtesy of Andreu World
What is the current global outlook on the recyclability of materials used in architecture? To what extent are contemporary societies truly committed to reducing environmental impact? In the effort to live in balance with nature, replacing fossil fuels with renewable energy sources is one of the key strategies for cutting greenhouse gas emissions and addressing global warming. Looking to nature for inspiration as a way to protect it means creating designs that incorporate sustainability, circularity, and recyclability from the very first sketch. From building systems to surface finishes, the use of biomaterials in architecture reflects a mindset rooted in long-term responsibility for a material's full life cycle.
Across Europe and beyond, architects are confronting a turning point. As rising emissions targets collide with shrinking material supplies and the growing urgency of climate commitments, the built environment is being forced into a deeper reckoning with how it consumes, circulates, and discards resources. What was once considered waste is now revealing itself as a dormant architectural archive, an urban ecosystem of materials waiting to be reclaimed, revalued, or reimagined. Within this shift, architects are beginning to play a radically different role. Not only as designers of buildings, but also as orchestrators of the flows that sustain them.
This emerging mindset is reshaping the foundations of practice. Instead of depending on long, extractive supply chains, designers are beginning to build their own closed-loop networks, establishing material banks, negotiating deconstruction protocols, and participating in new forms of urban mining.
Like the famous Russian Matryoshka doll, opening a package often feels like uncovering endless layers. Inside a cardboard box, there might be molded Styrofoam, then several plastic air pillows, and finally, individual plastic wrapping around each piece. Even a small product can leave behind a trail of plastic waste far larger than its size. Now imagine this logic applied to a construction site where every component, every delivery of materials, often arrives wrapped in multiple layers of protection. What already seems excessive in retail becomes monumental when repeated daily on large construction projects.
All materials come from somewhere, embedded in a chain of extraction, supply, production, and disposal that, depending on its scale, leaves more or less significant marks on the environment. In architecture, we usually approach this trajectory through the lens of materials' circularity, considering how they can re-enter production cycles rather than become waste. Yet, broadening our view to unexpected places reveals parallel systems where by-products from one industry become resources for another. This approach has found fertile ground in organic waste transformed into biomaterials, with one of the most recent examples being the work of Fahrenheit Works. Through their installation, "From the Tagus to the Tile", they repurpose oyster shells initially discarded by food systems to create a reinterpretation of Lisbon's iconic tiles.
In 2020, in the midst of the first wave of lockdowns due to the pandemic, the municipality of Amsterdam announced its strategy for recovering from this crisis by embracing the concept of the “Doughnut Economy.” The model is developed by British economist Kate Raworth and popularized through her book, “Doughnut Economics: Seven Ways to Think Like a 21st-Century Economist”, released in 2017. Here, she argues that the true purpose of economics does not have to equal growth. Instead, the aim is to find a sweet spot, a way to balance the need to provide everyone with what they need to live a good life, a “social foundation” while limiting our impact on the environment, “the environmental ceiling.” With the help of Raworth, Amsterdam has downscaled this approach to the size of a city. The model is now used to inform city-wide strategies and developments in support of this overarching idea: providing a good quality of life for all without putting additional pressure on the planet. Other cities are following this example.
At the end of each edition of the Architecture Biennale, far from the public eye, tons of exhibition materials are transported across Venice in handcarts and boats. Only a small portion of these materials is reused. The main obstacles are the limited storage space in Venice and the high logistical costs—recurring challenges for circular architecture. As a result, most of the waste ends up in landfills or nearby recycling centers. But this scenario is beginning to change. In response to growing environmental concerns, architects are developing strategies to make reuse more viable. These efforts go beyond architectural and construction decisions—they also involve logistics and international trade.
In recent years, architecture has increasingly embraced adaptability, flexibility, and responsiveness as core design principles. This evolution reflects a shift from traditional notions of static, permanent structures to dynamic environments that can adjust to changing needs and conditions. Central to this transformation is the concept of "soft architecture", which leverages pliable materials and innovative systems to create spaces that are functional, sustainable, and user-centric. Soft architecture takes shape through membranes that breathe, façades that move, structures that inflate or fold, and surfaces that bend rather than break. It involves designing for transformation — not only in how a building performs environmentally, but also in how it can accommodate shifting functions, user interactions, or temporary occupations. This approach to building challenges traditional notions of durability and control, proposing instead a more responsive and open-ended architecture. It reflects a growing awareness that buildings, like the societies they serve, must be able to evolve.
In partnership with the European Cultural Center (ECC), ArchDaily has launched its inaugural exhibition as part of the seventh iteration of Time Space Existence, an architectural showcase occurring concurrently with the 19th VeniceArchitecture Biennale. Open from May 10 to November 23, 2025, in various locations throughout Venice, this edition centers on the theme of "Repair, Regenerate, and Reuse," promoting innovative and sustainable approaches in architecture. ArchDaily's contribution is located at Palazzo Mora, complementing other venues like Palazzo Bembo, Marinaressa Gardens, and Palazzo Michiel.
