Intended to complement the adjacent historic Mitsui Main Building, the 40-story Mitsui Headquarters in Tokyo was designed to usher in a new era for the financial institution while retaining historical harmony with the area. The design of the project aspires to fulfill a need for urban renewal while creating an energy-efficient, low-management-cost building.
The 116,500-square-meter tower includes office space, a hotel with 250 rooms and a small shopping mall on the lower floors. Native cypress trees stand at four level intervals, representing an environmental interpretation of classical columns. Multi-purpose catwalks every four floors provide lateral bracing to transfer wind loads, support the native Cyprus trees at each bay and function as maintenance platforms for the interior glass surfaces. Exterior platforms mimic traditional Japanese overhangs on temple structures and are also used for lighting the trees for special holidays and other events.
To maximize energy efficiency, a double curtain wall provides an interstitial air space to minimize thermal gains and losses. A fan system, activated by photovoltaic panels, functions in the winter to move air heated by solar gain on the south to the north creating a balanced, tempered environment and reducing heat loss from the occupied spaces.