Green Roof Laws

Green rooftops are at the center of Tokyo’s long-standing policy efforts to reduce urban heat and strengthen environmental resilience. More than twenty years ago, the city introduced requirements under its Nature Conservation Ordinance mandating vegetated roof spaces on qualifying new and renovated buildings.

These rules apply to private buildings larger than 1,000 square meters, public buildings over 250 square meters, and large developments exceeding 10,000 square meters. In 2009, "the standards were expanded so that buildings above 5,000 square meters must green at least 25% of their roofs, while smaller buildings must meet a 20% target."

The initiative has produced significant ecological benefits. Additionally, "more than 5,700 buildings now feature green roofs, covering roughly 180 hectares." These installations lower rooftop temperatures by up to 25°C and reduce indoor heat by several degrees, decreasing energy demand for cooling and heating. They also improve air quality, support biodiversity, absorb stormwater, and reintroduce natural habitats into dense urban areas.

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