Green Space Area

Surugadai Building Surugadai Annex
Construction completed March 1984 February 2012
Site area 11,970m2 5,417m2
Building area 5,471m2 2,988m2
Rooftop green area 2,481m2 641m2
Ground-level green area 3,037m2 1,020m2
The percentage of green area 46% 31%

Soil structure

The soil depth of rooftop green is 1m on average, with 1.5m for areas with tall trees and 0.6m for areas with shrubs respectively. To maintain aggregate structure of soil long-term, the soil consists of Fuji sand and Kuroboku soil at 3:7 ratio with bark-type compost fertilizer worth 10% of its volume, allowing for good air and water permeability. This means plants survive mostly on rain water. The remaining rain water is used for toilets. To support this soil structure, the load capacity of the building is 2,000kg/m2 on average.

Heat Island Mitigation

Mitsui Sumitomo Insurance Surugadai Building Source: FY 2003 Chiyoda ward Research and engagements for heat island effects, etc.

The surface temperature of green spaces is more than 20°C lower than that of highways and rooftops of surrounding buildings, contributing to mitigating the heat island effect.