Now, a critical literature review published in Frontiers in Built Environment by Fujing Ma, Torsten Schröder, and Juliette Bekkering of Eindhoven University of Technology has taken aim at this conceptual fog. The team, based in the university’s Circular Built Environment Group, systematically analyzed academic papers and practice guidelines to clarify what circular renovation actually means, identify the barriers constraining its implementation, and synthesize the approaches available for one particularly urgent category of building stock: aged educational buildings. Their findings reveal a field that is expanding rapidly but remains fragmented, with definitions that diverge across scales, temporalities, and levels of abstraction.

The urgency is not abstract. Globally, the construction industry accounts for more than 32 percent of energy consumption, generates more than 25 percent of global solid waste, and is responsible for roughly 35 percent of total greenhouse gas emissions. Within the European Union, buildings account for about 40 percent of energy consumption and 36 percent of CO2-equivalent emissions. In the Netherlands, a country widely regarded as a circular economy frontrunner with a government-wide plan to make its economy 50 percent circular by 2030 and fully circular by 2050, a considerable share of higher-educational buildings built during the university sector’s expansion in the 1960s and 1970s are now approaching or exceeding their intended service life, showing marked deficits in energy performance, spatial functionality, and indoor environmental quality.

The scale of the challenge is considerable. In the EU, an estimated 17 percent of non-residential buildings are educational. The Netherlands alone has around 12,000 educational buildings totaling approximately 20.6 million square meters of floor area, with higher-educational buildings accounting for 62 percent of that total. Many of these structures, averaging over 40 years in age, can no longer fully meet current standards for energy efficiency, material performance, structural safety, functionality, or building regulations. Yet the review’s authors are careful to note that educational buildings do not require a fundamentally different set of circular renovation principles from offices or hospitals. What makes them distinctive is how shared principles—retention, reuse, life extension, adaptability, reversibility—are prioritized, combined, and implemented under their particular functional, spatial, pedagogical, and institutional conditions.

One of the review’s central findings is that circular renovation remains a less clearly defined concept than circular design. While circular design for new construction has developed into a relatively mature body of knowledge, supported by frameworks from Stewart Brand’s shearing layers theory to Cheshire’s building revolutions approach to the Ellen MacArthur Foundation and Arup’s Circular Building Toolkit, circular renovation has produced only six distinct definitions in the literature the team identified. These range from the Ellen MacArthur Foundation’s aspirational framing of durability and adaptability to DRIVE 0’s ambitious benchmark of renovation powered entirely by life-cycle renewable energy. Most, the authors conclude, function either as conceptual visions or strategic reference points, providing little decision support at the level of actual renovation practice, and none is tailored to the specific context of aged educational buildings.

To address this fragmentation, the review proposes its own definition: circular renovation of aged educational buildings is a systemic process of transforming existing buildings that integrates circular design principles with renovation practice, prioritizing the strategic retention, adaptation, and selective replacement of building elements across different layers. It does so by combining material circularity, energy performance improvement, and spatial adaptability, in order to extend both functional and building lifespans. Crucially, the definition bridges a gap that existing frameworks have largely ignored: the interrelationship between circular design and energy refurbishment. Of the six definitions analyzed, only DRIVE 0 explicitly incorporates energy renovation as a core component, leaving a significant conceptual divide between material loops and operational performance.

The review also maps the barriers to implementation with unusual precision, adopting a dual-lens classification that differentiates between renovation stages and building elements. Across five stages—pre-renovation assessment, design and decision-making, permitting and regulatory approval, construction and deconstruction, and operation and long-term maintenance—the barriers are cumulative rather than isolated. Information gaps span all five stages, reflecting persistent technical uncertainty, data fragmentation, and incomplete records. Regulatory barriers concentrate in the middle of the process, where compliance uncertainty for reused structural components and absent standards for reclaimed materials create procedural delays. Economic uncertainty emerges at the pre-renovation, construction, and operation stages, linked to high perceived upfront costs and the long-term erosion of circular value.

At the building-element level, the barriers materialize unevenly across what Brand called shearing layers—the site, structure, skin, services, space plan, and stuff that compose a building and change at different rates. Structural components, with their long service lives and high physical integration, resist disassembly and reuse, so circular strategies here prioritize preservation and life extension rather than component recycling. Envelope systems, though more frequently replaced, are multi-layered and tightly integrated with adhesives and membranes of low separability, frequently preventing dismantling without significant material loss. Building services—ventilation, heat recovery, heating, cooling, hot water, photovoltaics—have shorter lifespans yet are deeply embedded in structural and spatial systems, limiting modular replacement. Notably, installations can contribute up to 67 percent of the total embodied emissions associated with energy renovation measures, with 60 to 80 percent of their environmental impact occurring during production, highlighting the importance of circular design across service system lifecycles.

The review’s most distinctive contribution is its application of the shearing layers concept as an organizing lens to classify circular renovation approaches at the building scale. Because layers change at different rates, circularity cannot be applied uniformly but must be matched to each layer’s lifespan and functional role. For the structure layer, the highest-value circular strategy is retention and life extension, with reversible connections such as bolted steel and dry joints where replacement is unavoidable. For the skin, energy-efficiency measures like insulation upgrades converge with circular strategies like modular facade systems and reversible connections. For services, circularity emphasizes accessibility, modularity, replaceability, and upgradability rather than material durability alone. For space plan and stuff, flexible layouts and modular, repairable interior elements dominate. This layer-based classification converts broad circular design intentions into concrete, layer-specific interventions, showing how energy-efficiency and circularity measures align or compete at each layer rather than operating as separate agendas.

The authors acknowledge that their contributions are primarily a critical synthesis of a fragmented literature, along with modest conceptual extensions, and that the proposed definition and layer-based classification should be understood as hypotheses for testing rather than fully validated decision-making tools. The review relied on Scopus as its single primary database, restricted its search to English- and Dutch-language sources, and involved interpretive judgment in source selection. Still, the team outlines a future research agenda centered on what they call the circularity–energy–learning performance coupling: future work should address retention, disassembly, reuse, and lifespan extension; operational carbon, envelope, and system efficiency; and learning adaptability, flexibility, sharing, and hybrid learning as interdependent rather than separate objectives. Aged educational buildings, they argue, are not only technical objects but also learning environments that play a crucial role in inspiring future generations. Renovation projects can act as living laboratories, demonstrating how reuse, adaptability, and resource efficiency can be embedded in everyday spaces—and, when circular principles are made materially visible within students’ daily educational experience, they can shift awareness and inspire the practices that will define the built environment of the coming decades.

Subject of Research: Circular renovation of aged educational buildings

Article Title: Conceptualizing circular renovation for aged educational buildings: a critical review of definitions, barriers, and approaches

Article References: Ma, F., Schröder, T., & Bekkering, J. (2026). Conceptualizing circular renovation for aged educational buildings: a critical review of definitions, barriers, and approaches. Frontiers in Built Environment, 12, Article 1925223. https://doi.org/10.3389/fbuil.2026.1925223

Image Credits: AI Generated

DOI: 10.3389/fbuil.2026.1925223

Keywords: circular economy, circular renovation, educational buildings, shearing layers, building renovation, sustainability, Conceptualizing, circular, renovation, aged, educational, buildings

The scale of the problem is striking. Surveys of Swedish district heating utilities have found that leakages and faults in building internal heating systems are the most frequently reported fault categories. Studies indicate that up to 74 percent of buildings connected to district heating networks contain faults that elevate return temperatures, and an analysis of hourly meter readings from 135 substations in two Swedish networks found that roughly three quarters exhibited at least one fault or sub-optimal behavior. These customer-side faults compress the supply–return temperature differential, force higher distribution flow rates, and undermine the energy and exergy efficiency that low-temperature district heating is designed to achieve. In fourth-generation systems, which operate with narrower temperature margins than the 80–100 °C networks most buildings still connect to, such disturbances are even more consequential.

What makes the new framework unusual is that it embeds unsupervised machine learning models directly inside the building energy simulation loop. The researchers trained three anomaly detectors—a One-Class Support Vector Machine, an Isolation Forest, and a Local Outlier Factor model—exclusively on fault-free baseline data from a full heating season of a modified U.S. Department of Energy Retail Standalone commercial building, simulated in EnergyPlus with a 10-minute timestep and located in Västerås, Sweden. Six engineered features, including the instantaneous temperature error, a normalized hot-water mass flow ratio, a two-hour rolling mean of the comfort deviation, the zone temperature rate of change, outdoor temperature, and the hot-water supply–return differential, define the operating point. Because the models learn only the boundaries of normal operation, they can flag emerging deviations without requiring labeled examples of specific faults, which are scarce and expensive to collect in real buildings.

Once a sustained anomaly is confirmed by a temporal persistence filter, a signature-based diagnosis ladder classifies the fault as stuck-closed, stuck-open, or a supply-setpoint bias, and the supervisory compensation module ramps the supply-temperature setpoint toward a fault-specific target. The ramp follows a discrete first-order decay with a gain of 0.2, meaning roughly 90 percent of a requested setpoint change completes within 110 minutes. For under-delivery faults the target is 70 °C, boosting heat extraction through a restricted radiator; for over-delivery the target is 50 °C, throttling the thermal driving force. The compensated setpoint feeds back into the simulation at the next timestep, completing the closed loop with a one-step causal delay that a physically realizable controller could replicate.

The fault taxonomy deliberately spans physical and control failure mechanisms. A stuck-closed valve is a partial mechanical obstruction parameterized by a flow-restriction fraction, clamping hot-water flow to as little as 10 percent of the reference capacity. A stuck-open valve is implemented as a positive bias on the zone heating setpoint, reproducing the sustained overheating and compressed differential a mechanically seized valve would cause. The supply-setpoint bias extends the taxonomy to a system-level failure, depressing the hot-water loop temperature across all zones simultaneously, as might result from a drifted outdoor-temperature sensor or an incorrect reset-curve slope. Across 45 distinct simulations, the framework was tested at five severity levels per fault type, with parameter sensitivity sweeps and compound-fault stress tests probing the boundaries of supervisory controllability.

The headline results reveal a fault-type dichotomy in supervisory recovery potential. The stuck-open proxy fault achieved the highest comfort recovery at 68.8 percent of fault-induced discomfort degree-hours, while cutting hydronic energy use by 15 percent relative to the uncompensated fault and lowering the return-water temperature 4.2 K below baseline, a secondary benefit for network performance. The supply-setpoint bias achieved 57.2 percent recovery at a near-zero energy penalty, though compensation raised the return temperature 6.0 K above baseline because the unrestricted hydraulic path drives excess heat through the radiators. The physically constrained stuck-closed valve achieved only 38.6 percent recovery, because the mechanical flow restriction imposes a hydraulic ceiling that no supply-temperature boost can breach.

Detection performance proved strongly fault-dependent. The stuck-closed fault, with its pronounced combination of anomalously low flow and sustained underheating, was detected by a majority-vote ensemble with perfect recall and an F1-score of 0.90 within 20 minutes of onset, at a seasonal false-positive rate of just 0.18 percent. The stuck-open fault, whose overheating signal builds gradually across multiple features, required 100 minutes and achieved an F1 of 0.86. The supply-setpoint bias was the hardest to detect, with diffuse thermal signatures overlapping normal low-load conditions; none of 168 evaluated configurations exceeded an F1 of 0.52, though high recall ensured the compensation loop could still engage reliably.

Perhaps the most counterintuitive finding concerns feedback stability. For the stuck-open fault, successful compensation removes the overheating signature that triggered detection, causing the controller to release, the biased setpoint to reassert, and the cycle to repeat four to five times per occupied day—a sawtooth oscillation that caps net recovery. For the supply-setpoint bias, an asymmetric release logic with an extended hold sustains a single uninterrupted compensation block, eliminating cycling. The authors conclude that release logic design is as consequential for supervisory recovery as the detection algorithm itself, and that faults where compensation suppresses its own anomaly signature should employ fixed-duration holds rather than continuous re-detection.

Severity sweeps exposed practical detection floors and recovery ceilings. The mildest stuck-open bias of +0.5 °C is entirely undetectable, lying within normal zone-temperature variability, while detection becomes effective at +1.0 °C. For the stuck-closed fault, recovery peaks at a moderate restriction of φ = 0.20 and collapses at the most severe φ = 0.10, where the supply-temperature boost provides insufficient additional thermal driving force. Counterintuitively, detection F1 for the supply-setpoint bias peaks at moderate bias and declines at extreme severity, because very large depressions push the heating system into a regime resembling cold-weather normal operation rather than a distinct fault signature. The fixed anomaly thresholds also provide no severity estimation capability, a limitation for maintenance prioritization.

Compound-fault stress tests in diagnosis-only mode revealed the framework’s single-fault operational scope. When two under-delivery faults reinforce each other, the diagnosis remains action-consistent, correctly calling for a supply-temperature boost. But when a stuck-open bias partially cancels a supply-setpoint depression, the fixed-priority ladder commits to the wrong verdict on most alarmed steps, and parallel signature evaluation reveals conflicting control actions—reduce versus boost—on 80.7 percent of alarmed timesteps. The authors argue that an explicit abstain state with temporal confirmation is necessary to prevent erroneous compensation under concurrent faults. For physically constrained faults, the framework functions primarily as a diagnostic triage tool, providing rapid classification for priority maintenance dispatch, whereas control-type faults are viable candidates for immediate autonomous relief until maintenance is scheduled. Field validation in instrumented district heating substations remains the critical next step to assess sensor noise and unmodeled hydraulic dynamics before such systems can move from simulation into operational buildings.

Subject of Research: Building energy systems and district heating

Article Title: Integrated fault detection and supervisory compensation for hydronic radiator faults in district-heated buildings

Article References: Monghasemi, N., Vouros, S., Kyprianidis, K., & Vadiee, A. (2026). Integrated fault detection and supervisory compensation for hydronic radiator faults in district-heated buildings. Results in Engineering, 32, Article 113471. https://doi.org/10.1016/j.rineng.2026.113471

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113471

Keywords: Integrated, fault, detection, supervisory, compensation, hydronic, radiator, faults, district-heated, buildings, scientific research

The work forms part of the OLADAPT project, funded by Spain’s Ministry of Science, Innovation and Universities, and is being conducted in collaboration with the Polytechnic University of Madrid, the University of Extremadura and the UNESCO Chair in Sustainable Development and Environmental Education at the EHU. The researchers aligned their approach with the guidelines of the Intergovernmental Panel on Climate Change, which frame climate risk as the product of hazard, exposure and vulnerability. In the case of urban heat, that framing matters enormously, because the hazard itself—the temperature a given area experiences—is only one ingredient in the equation. How a city is built, which areas are hardest hit by high temperatures, and how many people are exposed and how little protection they have, all combine to determine the real risk to human health, thermal comfort and the liveability of urban spaces.

“We are looking at how to conduct a multi-dimensional and multi-scale assessment of the risk posed by heatwaves in urban areas. The risk posed by heatwaves is not measured solely by temperature; it has multiple dimensions,” explains Irantzu Álvarez, a researcher in the SAREN group, which is led by Leire Garmendia. That multidimensional perspective is what distinguishes the new methodology from coarser city-level assessments. Rather than treating a municipality as a single unit of analysis, the team measured vulnerability at the level of individual buildings and open public spaces, generating fine-grained vulnerability maps that reveal hotspots of risk that would otherwise remain invisible in aggregate statistics.

Building the maps required assembling a large volume of data drawn from a variety of sources. The researchers incorporated socioeconomic variables describing the people who live and work in each location, detailed characteristics of the buildings themselves, and environmental variables capturing the conditions of the surrounding urban environment. This combination is crucial, because sensitivity to heat depends on both the physical fabric and the human context. “A building may be sensitive to heat, but its residents may have the financial means to protect their home from it,” the researchers explain. In other words, a thermally poor building occupied by wealthy residents may pose less of a welfare problem than a marginally better building occupied by people with no means to install cooling, improve insulation or otherwise shield themselves from extreme temperatures.

The study’s most consistent finding across all three cities is the weight of socioeconomic variables in determining vulnerability. “People on low incomes, older people, etc. are far more vulnerable,” the research group states. This pattern held in Bilbao, Madrid and Cáceres despite their very different climates, suggesting that the social gradient of heat risk is a structural feature of Spanish cities rather than an artefact of any particular climate zone. Just as importantly, the analysis showed that vulnerability is not uniform within a city, and may even vary substantially within a single neighbourhood. It is therefore not enough, the researchers argue, to declare one city more vulnerable than another; detailed, building-by-building analysis is needed to locate the specific hotspots where intervention will save the most people from harm.

The choice of the individual building as the unit of analysis is what gives the methodology its practical power for municipal decision-making. “This methodology shows which buildings or types of buildings should be renovated or adapted first,” say Álvarez and Laura Quesada, the two researchers who spearheaded the analysis. Quesada is an architect specialising in the restoration and conservation of historic heritage and works at the Vitoria-Gasteiz School of Engineering, while Álvarez is a Technical Engineer in Surveying with a degree in Geography, based at the Bilbao School of Engineering; both lecture on the Master’s Degree in Construction Engineering at the Bilbao School of Engineering. Their combined expertise reflects the interdisciplinary character of the work, which spans building physics, urban geography and social science.

A second layer of the methodology links the vulnerability of buildings to that of the open public spaces around them. The researchers measured the impact of the surrounding environment on each building, capturing factors such as green cover and shade. “Buildings may be highly vulnerable but have plenty of green areas and shade around them. Taking all of this into account means that adaptation measures can be implemented in different ways,” the team explains. A vulnerable building in a leafy, shaded street may call for a different response than an equally vulnerable building on a hot, exposed plaza. By treating buildings and open spaces as an interconnected system rather than as separate problems, the maps allow planners to design adaptation strategies that operate at the scale of the streetscape as well as the individual structure.

The practical output of the methodology is a set of urban vulnerability maps that clearly indicate where priority action should be taken to tackle heatwaves. “Adaptation measures can be implemented much more effectively with this type of study,” the researchers say. For municipalities operating under tight budgets, this kind of prioritisation is invaluable: rather than spreading resources thinly across an entire city, officials can target renovation programmes, shading installations, green infrastructure and social support towards the buildings and neighbourhoods where the combination of physical exposure and social vulnerability is greatest. The maps thus translate abstract climate risk assessments into concrete, spatially explicit guidance.

Demonstrating the approach in three cities with distinct climates also served as a test of its transferability. “The methodology is fully replicable; it can be used anywhere. This makes the methodology more robust. It is a genuinely useful tool for municipalities and cities,” the group states. The successful application in Bilbao, Madrid and Cáceres suggests that the framework could be adopted by other cities facing intensifying heat risk, both in Spain and further afield, provided comparable socioeconomic, building and environmental data are available.

The broader context for this research is the steady escalation of extreme weather under climate change. Heatwaves are becoming more frequent and more severe, with direct consequences for public health, thermal comfort and the overall liveability of cities. Because urban populations are concentrated and much of the built fabric is long-lived, the decisions cities make now about which buildings to retrofit and which public spaces to green will shape heat resilience for decades. By demonstrating that vulnerability is a local, block-by-block phenomenon shaped jointly by poverty, age, building quality and the surrounding environment, the SAREN team’s work offers city governments a rigorous, replicable way to direct adaptation resources where they will matter most—and a reminder that the people least able to protect themselves from extreme heat are often concentrated in the very places that need help first.

Subject of Research: Multiscale GIS-based assessment of urban heatwave vulnerability in Spanish cities

Article Title: Vulnerability to heatwaves varies greatly from one area to another within cities

Article References: Vulnerability to heatwaves varies greatly from one area to another within cities. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: heatwaves, urban vulnerability, climate adaptation, socioeconomic factors, buildings, public spaces, GIS mapping, Bilbao, Madrid, Cáceres, IPCC, urban resilience

The methodology behind the estimate represents a significant advance in how scientists quantify the physical economy. Rather than extrapolating from sparse national statistics, the team constructed a building-level characterization that records the footprint, height, typology and inferred material composition of individual structures worldwide. By combining machine-learning classification of satellite and geospatial data with engineering relationships that translate a building’s geometry into mass of concrete, steel, masonry, timber and other materials, the researchers could weight each of the 606 million structures much as an accountant weighs each asset on a balance sheet. The result is a high-resolution global map of where material mass physically sits, from the reinforced concrete towers of East Asian megacities to the low-rise masonry neighbourhoods of Europe and the lightweight dwellings of sub-Saharan Africa.

The headline number, 835 gigatonnes, confirms that buildings dominate the material dimension of human civilization. Earlier work, including a landmark study published in the Proceedings of the National Academy of Sciences in 2017, showed that global socioeconomic material stocks rose twenty-three-fold over the twentieth century and that maintaining and expanding those stocks now requires roughly half of all annual resource use. The new building-level inventory sharpens that picture considerably by showing exactly which objects consume those resources. Buildings, it turns out, are the single largest store of anthropogenic materials, outweighing infrastructure, vehicles and machinery combined by a wide margin. Concrete and aggregate dominate the stock, followed by brick, steel and timber, with the mix varying systematically by region, income level and urban form.

What elevates the study beyond a bookkeeping exercise is its demonstration that material stock correlates strongly with urban form, and that urban form is a policy variable. Dense, compact cities with mid-rise and high-rise construction embody far less material per unit of floor area than sprawling, low-density development built with single-family homes. A detached suburban house may require several times more material per square metre of living space than an apartment in a well-engineered residential tower, because it spreads foundations, walls and roofs across a much larger footprint for the same usable area. The researchers show that cities which have grown vertically, whether in East Asia or in dense European cores, deliver housing and commercial space with markedly higher material efficiency than cities that have grown outward. The choice of urban form made today, in other words, is a choice about how many gigatonnes of stone, sand, iron and cement future generations will need to extract.

The inequality dimension of the findings is likely to spark the most debate. High-income countries hold a disproportionately large share of the global building stock relative to their populations, reflecting decades of accumulated construction, larger per-capita floor areas and heavier material specifications. Low-income countries, by contrast, face an enormous unfinished task: providing adequate housing, schools, clinics and workplaces for growing urban populations with building stocks that are materially thin. A household in a wealthy economy may be sheltered by hundreds of tonnes of embodied material, while a household in a low-income country may live within a structure embodying a fraction of that mass. Closing this material gap is a development imperative, yet it collides head-on with planetary limits, because the cement, steel and aluminium industries already account for a substantial share of global carbon dioxide emissions and industrial energy demand.

This tension frames what the study’s authors call efficiency paths. If low-income nations simply replicate the material-intensive development trajectories of the twentieth century, the global building stock could balloon in ways that climate targets cannot absorb. But the building-level database suggests alternatives. Material-efficient urban forms, compact neighbourhoods served by shared infrastructure, mid-rise construction that balances density with buildability, and designs that extend structural lifetimes and enable reuse of components, could deliver comparable human wellbeing with dramatically less new material. Scenario analyses published in Nature Communications in 2021 estimated that material-efficiency strategies in residential buildings alone could save billions of tonnes of resources and significant emissions, and the new global inventory provides the granular baseline needed to identify where those strategies would pay off most.

The technical achievement of characterizing 606 million buildings also matters for how cities are managed. Material stocks are not static; they are slow-motion flows. Every year, part of the stock is demolished and replaced, releasing construction and demolition waste, while new construction draws fresh resources from mines, quarries and forests. Knowing where materials are concentrated, how old they are and what they are made of allows planners to treat the existing city as a reservoir, an urban mine whose steel and concrete can be recovered and reused rather than discarded. It also enables more accurate life-cycle assessment, better forecasts of future demolition waste, and more precise carbon accounting, since the emissions embedded in a city’s buildings can now be estimated structure by structure rather than guessed from national averages.

The study builds on a rapid recent evolution in the field. A 2025 analysis in the Journal of Industrial Ecology produced the first global high-resolution map of building material stocks, and a 2024 study in Engineering used big geodata to reveal spatial patterns of built-environment stocks across and within fifty Chinese cities, showing that material intensity varies not only between countries but dramatically between neighbourhoods of the same city. The new Nature Cities work scales this building-level approach to the entire planet and adds the explicit inequality framing, quantifying the gap between the material abundance of wealthy urban systems and the material scarcity of poorer ones. In doing so, it connects two research communities that have often worked separately: industrial ecologists tracking global resource flows, and urban scientists studying the shape and growth of cities.

The implications reach into international climate negotiations, development finance and urban planning practice alike. For high-income countries, the findings suggest that the priority is not merely reducing new construction but managing an already massive stock efficiently, through renovation, densification, adaptive reuse and circular-economy strategies that keep existing materials in service. For low-income and middle-income countries, the findings argue for infrastructure and housing policies that leapfrog the most material-wasteful development patterns, adopting compact urban forms and efficient construction technologies before car-dependent sprawl and resource-hungry building standards become locked in. The 835 gigatonnes already in the ground cannot be un-built, but the next several hundred tonnes that humanity will inevitably add remain, for now, a choice. The new global inventory of the world’s buildings makes that choice visible, measurable and, for the first time, mappable at the scale of every structure on Earth.

Subject of Research: Global building-level quantification of urban material stocks and inequality

Article Title: Global characterization of building-level weight reveals urban material inequality

Article References: Global characterization of building-level weight reveals urban material inequality. (2026). Nature Cities. https://doi.org/10.1038/s44284-026-00509-w (Author names are not included in the publisher’s citation export.)

Image Credits: AI Generated

DOI: 10.1038/s44284-026-00509-w

Keywords: material stocks, built environment, urban inequality, buildings, concrete, material efficiency, urban form, sustainability, cities, resource use, Global, characterization