During Venice’s “Time-Space Existence” exhibition, Pritzker Prize-winning architect Alejandro Aravena and his firm ELEMENTAL, in collaboration with concrete manufacturer Holcim, unveiled a full-scale prototype of the USB Core Basic Service Unit housing. Centered on the concept of incremental development, this prototype is built using net-zero carbon concrete and 100% recycled aggregates. It aims to provide affordable, eco-friendly housing solutions for vulnerable groups, sparking widespread discussion in the architectural community about balancing residential needs with environmental protection—an exploration that aligns perfectly with the architecture latest trend of integrating social value with sustainability.
Material Revolution: A Breakthrough in Net-Zero Carbon Concrete
The key innovation of the USB Core prototype lies in its new concrete formula. By adding “biochar”—a type of charcoal that permanently sequesters carbon dioxide—each kilogram of biochar prevents the release of 3 kilograms of CO₂. Combined with low-carbon concrete technology, this achieves a negative carbon footprint. According to Holcim’s life-cycle assessment, under normal conditions (300 km of cement transportation and 100 km of aggregate transportation), the material ultimately reaches net-zero carbon emissions. Meanwhile, the prototype uses recycled aggregates throughout the construction process, reducing the extraction of natural resources and practicing the concept of a circular economy, thus offering a new path for the low-carbon transformation of the construction industry.
Incremental Concept: Solving the “3S” Dilemma in Housing
Aravena points out that global housing currently faces the “3S” challenges: Scale, Speed, and Scarcity of means. Millions of people move to cities every week, and without proper accommodation, slums will breed health crises and social problems. Taking Chile as an example, two housing censuses show that two-thirds of built areas lack construction permits, and traditional construction processes fail to meet real needs.
Aravena’s team found that the crux of slum issues is not “too few buildings” but “lack of public space.” In cities like Copenhagen and Manhattan, the ratio of public to private space is approximately 1:1, while in slums, it drops to as low as 1:10, leading to blocked emergency access and no activity areas for residents. Therefore, the USB Core prioritizes public space planning, providing fire-resistant and earthquake-resistant basic structures, as well as water, electricity, and sanitation facilities. Residents can later independently improve interior decorations, which not only reduces initial costs but also safeguards the public interests of the community.
In Aravena’s view, when addressing housing problems, architects need to abandon the traditional mindset of “controlling the final product” and shift to “designing the process.” He cites Chile’s “Chalk Operation” as an example: by simply drawing lines to define the boundaries between private and public spaces, spontaneous construction can be standardized and public interests protected. “We are not providers of resources, but guides of forces,” he emphasizes. The two-story design of the USB Core not only meets policy requirements for sanitation facilities, fire resistance, and earthquake resistance but also reserves space for future high-density development, helping residents settle in the city center instead of being marginalized to the suburbs.
This role shift is reflected in detailed designs: the prototype uses robotic formwork construction, which reduces weight while creating diverse patterns. This not only meets structural strength requirements but also builds an emotional connection between residents and their homes through aesthetic design. “Aesthetics should not be sacrificed under harsh conditions,” Aravena believes. Customized details make residents feel respected and enhance their sense of community belonging.
Cross-Industry Collaboration and Future Outlook
Aravena admits that the construction industry is essentially “the art of collaboration.” The implementation of the USB Core would not have been possible without technological research and development with Holcim, policy coordination with the Chile government, and in-depth listening to residents’ needs. He hopes that in the future, financial institutions will include the application of zero-carbon materials in loan conditions to promote the large-scale promotion of such solutions.
“This is not a single project, but a new tool in the toolbox,” Aravena says. The ultimate goal of the USB Core is to enable housing construction to no longer choose between “meeting needs” and “protecting the environment.” Instead, it uses innovative technologies and concepts to achieve a win-win situation for both social and ecological values. Currently, the prototype has become the focus of the Venice’s “Time-Space Existence” exhibition, providing a replicable practical model for global housing issues.
