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.
During the Time Space Existence exhibition, organized by the European Cultural Centre in Venice, Pritzker Prize-winning architect Alejandro Aravena and his firm ELEMENTAL unveiled a full-scale prototype for a new approach in incremental housing solutions. Titled the USB Core, standing for Basic Services Unit housing prototype, this proposal aims to demonstrate how efficient construction can provide all the essential housing components in a minimal space. The prototype is also the result of a collaboration between the architecture office and concrete manufacturer and researcher Holcim, and is built out of a newly developed type of net-zero concrete mix. It also incorporates fully recycled aggregates, in alignment with circular economy principles. The collaboration aims to demonstrate a more environmentally conscious yet cost-effective way of providing essential services to at-risk communities without harming the planet.
While on site in Venice, ArchDaily's managing editor Maria-Cristina Florian had the chance to sit down with Alejandro Aravena and discuss the implications of this collaboration, the urgent need for housing, and the role of the architect as the coordinator of a process involving many actors.
Material intelligence refers to how materials perform, adapt, and interact with ecological and cultural systems. It considers how stone, steel, or timber respond to intertangled forces, how those materials are sourced and assembled, and how they persist after demolition. Designers are centering material intelligence in constructing our cities in a generation of environmental uncertainty and strained supply chains.
Officially open since April 13 as part of Expo 2025 Osaka, the German Pavilion, designed by LAVA Architects. brings to life the theme of the circular economy. Previously unveiled under the title "Wa! Doitsu" (translated as "Wow! Germany"), the Pavilion explores concepts around circularity, showcasing the "terminological culmination of the sustainability discussion." Focusing on returning all consumable goods to the cycle of the economy, achieving zero waste, and minimizing resource consumption, the theme is visible throughout the entire design.
In a context where sustainability and material identity are becoming priorities in architecture, some ancient materials are finding new life. Terrazzo, with origins dating back to the 15th century, stands out as an example of how tradition can fuel innovation. The modern form, as we know it today, emerged in 15th-century Venice, Italy, when Venetian mosaic workers, seeking to make use of marble scraps, began incorporating these irregular fragments into mortar to create durable and visually appealing surfaces for terraces around their homes. This approach not only minimized raw material waste but also led to the development of new surface-finishing techniques, evolving from manual stone rubbing to the use of a heavy, long-handled grinding stone known as a galera.
