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Good practice Imported

Tokyo's Nature Conservation Ordinance — Mandatory Rooftop & Wall Greening for New Buildings

Japan · Tokyo · See the Japan profile · See the Tokyo profile

Evidence: Descriptive / self-reported Top 58% 40/100 · Ask Evidence Copilot about this practice

Since 2001, Tokyo has legally required new and renovated buildings above set size thresholds to green 20-25% of their roof area; the mandate has added roughly 180 hectares of green roofs across more than 5,700 buildings citywide.

5,700+
Buildings compliant
180 hectares
Green roof area added citywide
1,000 hectares
Original 2016 target
up to 25 C
Rooftop surface-temperature reduction (lightweight green roofs) (2004 study)
Tokyo's Nature Conservation Ordinance — Mandatory Rooftop & Wall Greening for New Buildings

Details

Maturity
Established
Promoter
Tokyo Metropolitan Government (Bureau of Environment)
Period
2001-present
Keywords
urban greening, green roofs, green walls, building regulation, heat island mitigation

Context

The Tokyo Metropolitan Government's Nature Conservation Ordinance, enacted 2001, requires private buildings over 1,000 m2 (250 m2 public) undergoing new construction or major renovation to green at least 20% of usable rooftop area; a 2009 amendment raised this to 25% for buildings over 5,000 m2.

Results

By the time of C40's case study, more than 5,700 buildings had complied, adding about 180 hectares of green roofs citywide, against an original target of 1,000 hectares by 2016. A 2004 study found lightweight green roofs could lower rooftop surface temperatures by up to 25C.

Conclusions

The achieved total fell well short of the citywide target, and no independently published biodiversity or stormwater-retention monitoring tied to the mandate was found.

Implementation
Indicative cost
Low (< €50k)
Time to results
Long (> 3 years)
Staffing & skills
Tokyo Metropolitan Government Bureau of Environment permitting staff

Conditions for success

  • Consistent building-permit enforcement
  • Developer compliance with green-area thresholds

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Data sources

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