The Global Layer

Abstract

Cities face converging building-performance problems — envelope heat-loss, HVAC decarbonization, embodied carbon in concrete and steel, and construction-and-demolition waste — and diverging regulatory vocabularies. New York codifies operational emissions through Local Law 97 of 2019. Denmark encodes embodied-carbon thresholds through Bygningsreglement BR18 §297. The European Union, through the recast Energy Performance of Buildings Directive 2024/1275, mandates material passports for all new buildings over 1,000 square meters beginning in 2028. California applies CALGreen Tier 1 and Tier 2 to public and private construction. Japan operates the METI Top Runner Program for equipment efficiency and is extending analogous logic to the building stock.

These frameworks are not, in the computer-science sense, the same rule. They are — increasingly — the same concepts expressed in different forms. Large language models operating over a shared semantic layer, combined with formal rule engines derived from building-code ontologies, can translate between them. A BIM file authored in Copenhagen can be tested against LL97 in New York. A material passport produced in Amsterdam can be priced into a reclaim market in Tokyo. This chapter argues that AI is the translation layer, and that federation — not harmonization — is the policy objective. Federation means compatible schemas and machine-readable rules, not a single global building code.

The chapter proceeds in six moves. It (1) surveys cross-jurisdiction rule engines; (2) describes federated material passports; (3) examines transferable climate-resilience models; (4) presents a six-city peer scorecard; (5) outlines the standardization battle between open and proprietary digital-twin formats; and (6) closes with three implications for policy and capital allocation in the 2026–2030 window.

Cross-jurisdiction rule engines

A building code is, structurally, a collection of rules keyed to building attributes — use, area, height, envelope assembly, occupancy, material quantity. When the rule and the attribute are both machine-readable, a compliance check becomes a function call. LL97 is written in English and enacted in New York Administrative Code Title 28, Article 320, but the binding obligations are numerical: emissions intensity caps measured in kilograms of CO equivalent per square foot per year, by building occupancy group, across compliance periods of 2024–2029 and 2030–2034. Those caps can be represented as a rule table the size of a small CSV.

Bygningsreglement BR18 §297 is the comparable Danish construct for embodied carbon: a limit of 12 kilograms CO per square meter per year, averaged over a 50-year reference period, for new construction over 1,000 square meters — now tightening on a published schedule. Directive (EU) 2024/1275 sets analogous zero- emission and whole-life-carbon disclosure requirements across the 27 member states. California's CALGreen Code (2023 edition) incorporates Tier 1 and Tier 2 thresholds for material reuse, recycled content, and construction-waste diversion that mirror a subset of the EPBD requirements. Japan's METI Top Runner Program covers appliances and equipment, and serves as the template for an emerging buildings-sector analogue.

Expressed as rules over a shared schema — IFC 4.3 as the geometric and semantic substrate, ISO 19650 as the information-management envelope — each of these frameworks becomes queryable against the same model. A developer with a BIM file can, in principle, run the feasibility of the same design across five jurisdictions in minutes. The technical capability exists. The blocker is that the rule expressions themselves live in PDFs, not in shared machine-readable repositories. Projects such as buildingSMART's IDS (Information Delivery Specification) and the EU's Digital Building Logbook initiative are the first credible candidates for that repository layer.

The pattern recognition that LLMs supply is the translation from legal text to rule. The formal rule engine — still necessary — is what makes the result auditable. The combination is, in the literature, typically called "neuro-symbolic" compliance checking. It is the specific architecture that allows LL97 to speak to BR18 without either becoming the other.

Federated material passports

A material passport is a structured record of what a building is made of — quantities, grades, provenance, and end-of-life pathways. Directive (EU) 2024/1275 requires them on all new buildings above 1,000 square meters starting in 2028 and, through the companion Construction Products Regulation revision, on the products that go into them. Denmark, the Netherlands, and France have national implementations at various stages. The Ellen MacArthur Foundation's Building Prosperity (2024) and Circle Economy's Circularity Gap Report (2024) both argue that passport adoption — more than any single demolition tax or landfill ban — is the lever most likely to shift material flows at continental scale.

The technical basis is already in place. buildingSMART International's IFC 4.3 supports the object classes a passport requires. ISO 19650 defines the information-management process. RICS's Whole Life Carbon Assessment, 2nd Edition (2023), defines the carbon accounting boundaries. The remaining work is schema interoperability: if NYC, Tokyo, Amsterdam, and Copenhagen each adopt a different dialect, a reclaimed steel beam in one city is illegible to a buyer in another. If they adopt compatible dialects — not necessarily identical ones — the reclaim market becomes continental rather than municipal.

The economic consequence is direct. A reclaim market at municipal scale is dominated by logistics costs and idiosyncratic local supply. A reclaim market at continental scale, matched through a federated passport registry, can sustain the liquidity that an industrial reuse economy requires. The EPBD 2028 deadline functions, in effect, as a forcing function for schema interoperability. The cities that arrive at the deadline with compatible passports will participate in that market. The cities that arrive with incompatible ones will remain local.

Transferable climate-resilience models

Urban-heat-island models trained on NYC LiDAR, LL84 benchmarking disclosures, and the Mayor's Office of Climate and Environmental Justice surface-temperature survey generalize, with domain adaptation, to other dense coastal cities with analogous rooftop density and albedo distributions. MIT Senseable City Lab's working papers through 2024, and the C40 Cities Clean Construction Declaration signatories' shared datasets, indicate that the dominant predictors — impervious-surface fraction, building-height variance, and tree canopy — are portable across Boston, Rotterdam, Melbourne, and Singapore.

Flood-resilience models are similarly transferable. Copenhagen's Cloudburst Management Plan (2012), the canonical response to the 2011 cloudburst event, has been reused as a reference architecture by cities from Hamburg to Auckland. NYC's post-Sandy planning — including the DEP Citywide Long-Term Control Plan and the Mayor's Office of Resiliency's neighborhood-level strategies — is a second reference architecture for high-surge, low-gradient coastal geometry. A model trained on one can be fine-tuned to the other with comparatively small local samples.

The value of transferability is not that cities avoid doing local work. They cannot; hydraulics and microclimate remain local phenomena. The value is that the hypothesis space is already populated. A planner in Osaka does not begin from first principles. A planner in Miami does not either. This is a qualitatively different starting condition than the one that existed a decade ago — and it is what makes the global layer analytically meaningful rather than merely rhetorical.

The standardization battle

Three formats are competing to become the substrate of the global layer. buildingSMART International's IFC (Industry Foundation Classes), now at version 4.3 with BCF 2.1 for issue-tracking, is the open, ISO-ratified option — ISO 16739-1:2024 — with the largest installed base in public-sector procurement. Autodesk Forma, the successor to Spacemaker, is the proprietary counterpart backed by the dominant authoring-tool vendor; its 2024 research publications suggest an open-API strategy but not open semantics. ESRI's ArcGIS Urban and associated 3D basemaps occupy the urban-scale digital-twin layer with a tight integration to the GIS installed base.

The question is not which format is technically superior. Interoperability questions rarely resolve on technical merit. The question is which format accumulates the public-procurement mandates that lock in the next decade. The EU — through the EPBD's Digital Building Logbook provisions and the European Commission's eBIM procurement guidance — is explicit that open standards are the default. The United States is less explicit; federal General Services Administration and U.S. Army Corps of Engineers BIM mandates specify IFC as a deliverable but do not restrict authoring tools. The near-term trajectory is a bilingual market: IFC as the contractual artifact, proprietary formats as the authoring environment. Whether that bilingualism holds, or whether a single format dominates by 2030, is the live question.

The stakes are federation versus vendor lock-in. A global layer built on open semantics scales to every city that adopts the standard. A global layer built on a proprietary format scales only where the vendor is present and only at the price the vendor sets. The first is an infrastructure good. The second is an enterprise product. The difference, at the 30-year horizon that building stock operates on, is the difference between a public utility and a toll road.

What this means

1. The first open, AI-queryable building dataset becomes the de facto global standard.

Standards do not win on elegance. They win on corpora. Whichever city publishes the first complete, open, machine-readable building-performance dataset — geometry, operational energy, embodied carbon, material inventory, and compliance status, under a permissive license — will supply the training data against which the next decade of models are calibrated. That dataset will become, by default, the reference schema. The competitive window is narrow. The EPBD 2028 deadline is the forcing function. NYC, with LL84 and LL97 disclosures already public, is structurally well-positioned; so is Amsterdam, which has already released much of its 3D BAG and passport work under open licenses. The window closes when one of them ships end-to-end.

2. Federated material passports are the largest available circular-economy multiplier in 2026–2030.

The sector-level literature — Ellen MacArthur Foundation's Building Prosperity, Circle Economy's Circularity Gap Report, and the European Commission's own impact assessments for EPBD 2024/1275 — converges on a single claim: continental-scale reclaim markets require passport compatibility more than any other single intervention. Demolition taxes, landfill bans, and extended-producer-responsibility regulations each contribute at the margin. Passports are the structural lever. Their adoption, if federated, measurably compresses the embodied-carbon footprint of new construction by creating a liquid secondary market for structural steel, concrete elements, and façade components. Their adoption, if fragmented, produces small local markets that clear at low volume and disappear under transport cost.

3. Fragmentation is the default failure mode.

If NYC, Amsterdam, and Tokyo each adopt incompatible schemas — even accidentally, through divergent national implementations of EPBD or through proprietary twin formats tied to single-vendor procurements — the global circular market collapses to local maxima. Each city optimizes within its own boundary; cross-border flows remain at the hand-carried, artisanal scale they currently occupy. The risk is not the absence of regulation but the presence of too many mutually unintelligible regulations. The policy response is not harmonization — which is politically unavailable and probably undesirable — but federation: shared schemas, shared rule expressions, and machine-readable equivalence mappings between national codes. The infrastructure for that federation is the global layer this chapter describes.

Sources

• Directive (EU) 2024/1275 of the European Parliament and of the Council of 24 April 2024 on the energy performance of buildings (recast). Official Journal of the European Union.
• Bygningsreglement BR18 §297. Trafik-, Bygge- og Boligstyrelsen (Danish Housing and Planning Authority), 2023 revision.
• California Building Standards Commission. CALGreen (2023 California Green Building Standards Code), Title 24, Part 11.
• New York City Local Law 97 of 2019 (Emissions from Large Buildings). NYC Administrative Code Title 28, Article 320.
• Ministry of Economy, Trade and Industry (Japan). Top Runner Program, current equipment list and methodology, METI 2023 update.
• buildingSMART International. IFC 4.3 (ISO 16739-1:2024); BCF 2.1; Information Delivery Specification (IDS).
• International Organization for Standardization. ISO 19650-1/-2 Organization and digitization of information about buildings and civil engineering works.
• Ellen MacArthur Foundation. Building Prosperity: Unlocking the Potential of a Circular Built Environment (2024).
• Circle Economy. Circularity Gap Report 2024. Amsterdam.
• Kobenhavns Kommune. Cloudburst Management Plan (2012); Copenhagen Climate Plan 2025.
• Gemeente Amsterdam. Amsterdam Circular Strategy 2020–2050; Circular Monitor (2024).
• Ville de Paris. Plan Climat (2024); Décret Tertiaire (Decree n° 2019-771).
• Tokyo Metropolitan Government. Climate Change Adaptation Plan; Tokyo Cap-and-Trade Program (2010–).
• Building and Construction Authority (Singapore). Green Mark scheme; Super Low Energy Buildings 2030.
• MIT Senseable City Lab. Working papers on urban-heat-island and rooftop-albedo modeling, 2023–2024.
• C40 Cities. Clean Construction Declaration and signatory reporting, 2023–2024.
• NYC Department of Environmental Protection. Citywide Long-Term Control Plan, most recent amendment.
• Royal Institution of Chartered Surveyors. Whole Life Carbon Assessment for the Built Environment, 2nd Edition (2023).