Hands to Reclaim the Green City: The Beginning and Spread of Mandatory Rooftop Gardening in Kyoto (2007)

Hands to Reclaim the Green City: The Beginning and Spread of Mandatory Rooftop Gardening in Kyoto (2007)

In the early 2000s, Japan began to take heat island countermeasures in earnest as a national policy. From 2002 to 2004, the government developed the "Outline of Urban Heat Island Countermeasures," which focused on structural improvements, greening, and high-reflectivity. Rooftop greening was institutionalized as a major means of reducing the heat capacity of cities, and each municipality established ordinances mandating and guiding such measures.

In Kyoto, landscape and environmental policies were integrated in 2007 to clarify the policy of simultaneously improving the urban thermal environment and landscape. In the same year as the renewal of the landscape policy, the city put into operation a specific greening building system, making greening of buildings and sites mandatory for newly constructed or reconstructed buildings with a site area of 1,000 square meters or more in urbanization zones. The system required greening of at least 20% of the rooftop area, and was implemented in areas covering 11 cities and 7 towns in the prefecture.

This system functioned not only as a landscape improvement measure, but also as an urban thermal environmental measure. The introduction of a water-retaining lightweight greening base and a heat-insulating construction method reduced the temperature rise in buildings and reduced the cooling load. With the cooperation of citizens and businesses, greening has also spread to temples, shrines, and commercial facilities.

The background of this trend is the global warming countermeasure trend triggered by the Kyoto Protocol that came into effect in 2005. Kyoto Prefecture and Kyoto City positioned the mandatory greening as a "symbiosis of culture and the environment" and promoted it as an urban policy to bring back wind and greenery from the rooftops of cities. The greenery sprouting on rooftops has transcended the heat island and has become a symbol of the historical city creating the environment of the future.