Green Space Area

The percentage of green area is 43%. Out of 4.7ha (2003 data) of all rooftop green areas in Chiyoda-ku, its rooftop green area accounts for 5.5% of it.

Construction completed March 1984
Site area 11,970m2
Building area 5,471m2
Rooftop green area 2,614m2
Ground-level green area 2,561m2

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.

Cooling down rooftops

We cooled down the upper rooftop of Surugadai Building by applying high-reflectivity coating on it. Cooling down the rooftops largely lowers the rooftop surface temperature, thereby helping to mitigate the Tokyo Heat Island effect.

Awards and Prizes

  1. 1993
    Urban Landscape Award (Director of Chiyoda Ward)
  2. 2001
    Green Achievement Award (Minister of Land, Infrastructure and Transport)
  3. 2004
    Green Rooftop Award (Minister of Environment) :News Release Mitsui Sumitomo Insurance Co., Ltd. Oct.22, 2004
  4. 2005
    SEGES (Urban Green Space Development Foundation) :News Release Mitsui Sumitomo Insurance Co., Ltd. Apr.28, 2005
    Sustaining accreditation of highest rank achievable: Excellent Stage3

Media coverage


NHK General TV Good morning Japan Apr.8, 2005
Nippon TV Unexpected Stopover Trip Sep.30, 2006
Tokyo TV Chie no Wa Oct.1, 2006
Fuji TV Meza nyu- Nov.22, 2006
Nippon TV Omoikkiri TV Dec.19, 2006
NHK General TV Newswatch 9 May 4, 2007
BS Asahi Happy! Lohas May 4, 2007


Yomiuri Weekly Jun.19, 2005 issue
Nihon Keizai Shimbun Sep.28, 2005 evening edition
AERA Oct.31, 2005 issue
SPA Weekly Oct.17, 2006 issue
Yomiuri Shimbun Nov.18, 2006 evening edition
Shincho Weekly Dec.1, 2006 issue
Croissant separate issue Mar.10, 2007 issue
Asahi Shimbun May 8, 2007 evening Edition


TBS Radio Kyokei Arakawa's Day Catch Oct.16, 2006