Can AI read and cite building energy laws across 119 cities? That is the data collection challenge behind the next edition of Building Green, the World Bank Group’s dataset on building energy codes and their enforcement, due in spring 2027. The dataset pairs two types of data: what the law requires, researched from published legal sources, and what happens in practice, reported by local experts. For the legal half, we put AI to the test: OpenAI’s GPT-5.4 Mini drafted answers to 60 legal questions per city, each tied to an exact excerpt from the law; Anthropic’s Claude independently reviewed the legal basis; and analysts checked every answer. In the first 21 economies reviewed, about four in five answers were correct, at roughly US$27 per city in model costs and an estimated 1,500 researcher hours saved.
The stakes are high. Buildings and construction account for around 37 percent of global CO2 emissions, and energy codes are one of the main tools governments use to set efficiency standards for new construction. But a code on the books is not a code in practice. That gap is at the heart of Building Green. Its first edition, published in 2024, found that across 88 economies with a mandatory code, just over a third had a functioning system for qualifying and overseeing the inspectors who check compliance.
The next edition covers 119 cities in 110 economies.
What AI can and cannot answer
Data on regulations and their enforcement are collected through two complementary questionnaires.
The regulatory data are matters of record — whether a requirement is mandatory, which law establishes it, what penalties apply — and can be traced to official sources such as gazettes, ministry websites, and standards. This questionnaire covers 60 questions per city, answered by AI, with each answer carrying its legal basis, an exact excerpt, and a URL.
The enforcement data exist in no official source: how consistently a requirement is applied, how long a compliance review takes, whether the local workforce and market can deliver what the code requires, and whether incentives work in practice. These answers come from the architects, engineers, and officials who work with the process, through a separate expert questionnaire.
