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CASE STUDY:
French Embassy

Tokyo, Japan

French Connection: Supported by piloti and board formed concrete, Tokyo’s new French Embassy bows politely to the past while its high CASBEE rating bodes well for the future.

ADPI; Takenaka Corporation

By Naomi Pollock, AIA

Ever since the dawning of Modernism, Japan has been in love with French architecture. While the United States looked to Mies van der Rohe, Japan only had eyes for Le Corbusier, who trained several of the country’s most notable architects and whose buildings influenced legions of others. The product of an international consortium of designers and developers, Japan’s new French Embassy bows politely to that legacy. Combining the best of both worlds, this slender structure with its piloti and board-formed concrete embodies Parisian elegance but stands in the heart of Tokyo.

French Embassy, Tokyo, Japan
Photo © Kawasumi Architectural Photograph Office
French Embassy, Tokyo, Japan

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KEY PARAMETERS
Location: Tokyo, Japan (Tokyo Bay watershed)
Gross area: 91,000 ft2 (8,454 m2)
Completed: October 2009
Annual purchased energy use (based on simulation): 60 kBtu/ft2 (680 MJ/m2)
Annual carbon footprint (predicted): 22 lbs. CO2/ft2 (110 kg CO2/m2)
Program: Offices and residences

 

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Temp./Dew Points   Precipitation
Temp./Dew Points   Precipitation

TEAM
Owner: French Ministry of Foreign Affairs
Architect: ADPI; Takenaka Corporation
Interior design: Takenaka Corporation
Engineers: Takenaka Corporation
Lighting consultant: LSA
General contractor: Takenaka Corporation

SOURCES
Glazing: Saint-Gobain
Skylights: NSG
Carpet tile: Toli
Office furniture: Okamura
Reception furniture: K and Company

The project began in the 1990s when the French government decided to replace the existing building designed in 1957 by Jean Demaret and Joseph Belmont. Situated within the 270,000-square-foot property acquired in 1921, it was seismically unsound, functionally deficient, and too small. Adopting a public-private strategy, the French government held an open competition for an ecologically sensitive embassy. “Since this project represents our country, we wanted it to showcase our concern for environmental quality,” explains Rudolf Etienne, director of property management for the Pacific-Asia Area, French Ministry of Foreign Affairs.

They awarded the commission to the team comprised of both developers and architects. In exchange for a 53-year lease on a one-acre portion of embassy land where they could build condominiums, the developers agreed to pay for the embassy’s design, construction, and maintenance for 15 years, plus fund the renovation of the ambassador’s residence and other embassy properties in Japan.

For the competition, Aeroports de Paris Ingenerie devised the project’s basic plan but afterwards Takenaka, one of Japan’s leading design-build construction companies, saw the project through to completion. Kume Sekkei participated as technical advisors and construction supervisors. The winning scheme proposed separate volumes for the visa section and embassy offices respectively. Fronting the street, the visa building holds processing and waiting areas plus a check-point since it doubles as the gateway to the entire compound. From here, a ramp leads up to the offices, a 91,000-square-foot building entered through a 4-story atrium lobby flanked by two wings. Perched on piloti, the west wing holds the porte cochere, parking, and mechanical room at grade plus four floors of offices and service spaces. The east wing starts with parking followed by three floors of offices and staff apartments topped by the ambassador’s secluded suite.

This site strategy had several advantages. Dividing the embassy’s public and private functions appealed greatly from a security point of view. And placing the main building along the southern edge of the property minimized the impact on the existing ambassador’s residence to the north and the site’s mature forest in the middle. Utilizing the ground’s southward slope, the architects located the new construction 66 feet below the residence to preserve the home’s tree-filled view. This entailed removing a small segment of the hill at the west end and bolstering the hill with a concrete retaining wall. Sculpted to resemble rocks, the stepped wall incorporates planters whose greenery enlivens the approach to the new building.

Thanks to the glass facade, the architects were able to enhance the building interior with the old and new growth. Concentrated on the building’s north side, the offices have unimpeded views of the densely wooded landscape while service spaces, such as lavatories, kitchenettes, and storage, line the building’s concrete-paneled south side. Designed to edit the large apartment block next door, the opaque wall also reduces the heat load. But the transparent facade has energy conservation benefits too. Composed of insulated, double-paned glass, the curtainwall helps maintain indoor comfort and facilitates the building’s natural ventilation system.

In addition to hand-operated windows that regulate individual offices, a computer-controlled system creates a chimney effect that modulates the temperature and air circulation throughout the building. In response to roof-mounted sensors that evaluate outdoor conditions, including wind velocity and humidity, the computer instructs intake vents on the facade to admit fresh air. Passive ducts direct the flow into the corridors, and clerestory windows ringing the atrium’s glazed roof draw the air up and out. Taking advantage of Tokyo’s mild climate, this system curtails the use of mechanical air handling during the many months when temperatures range between 59 and 86 degrees Fahrenheit. “The system needs some warm air but not too much,” explains Takenaka mechanical engineer Yuuhi Sonoda. Consequently, in the dead of winter or peak of summer, a gas heat pump takes over.

While gas is not commonly used in Japanese office buildings, it is cheaper than electricity in the long run and can be restored quickly after earthquakes. Since the embassy must continue to function during major disasters, earthquake readiness was an important consideration for all aspects of its design and construction. Regarding structure, conventional reinforced concrete was sufficient for the visa building. But the offices’ steel frame rests on seismic isolators that reduce lateral forces drastically. This, in turn, made it possible to use smaller columns and beams. “Essentially the entire building is floating on rubber,” says Takenaka architect Daishi Yoshimoto, AIA. As a result, the architects were able to lessen the dead space above the ceiling and create a lower building without compromising the 9.5-foot height in the offices.

Arranged in an 18-foot grid, the slender columns fit neatly within the 20-square-foot module commonly used in France—the standard that guided the size and placement of everything from window mullions and room partitions to electrical outlets and light fixtures. “You can take a door from one place and use it interchangeably in the building,” explains Yoshimoto. This flexibility allows the client to easily reconfigure rooms with minimal waste. “Embassies tend to reorganize quite often so we requested an adjustable building,” says Etienne.

In addition to reusable building parts, the architects chose many materials with ecological benefits such as carpet and recycled wood decking stamped with Japan’s Eco-Mark certification. But conservation was not their sole criterion. To distinguish the embassy from a commercial office building, the architects used wood to denote public areas and brightly color-coded the corridors on each floor. And because the exterior had to be distinctive and durable, board-formed concrete and aluminum cladding cover the visa building and its bold roof, while polished concrete panels dotted with green granite chunks and white limestone pebbles comprise the offices’ solid walls. Aside from select windows, the only glass on the building’s backside encloses the internal stair.

An enticement to walk instead of ride, the open, wood stair admits southern light and is a visual focal point of the atrium. Capped with clear glass, the embassy’s airy core is filled with daylight that permeates adjacent spaces and diminishes the need for artificial illumination. Even the double-loaded corridors use only low-level fixtures, thanks to the atrium and the glass partitions that let in light from the offices.

High quality working conditions were one among many considerations evaluated for a Comprehensive Assessment System for Built Environment Efficiency (CASBEE) rating. Japan’s LEED equivalent, the CASBEE system is based on a ratio of the building’s tangible and intangible qualities to the load it places on the environment. “Any building will have a negative impact but if the good outweighs the bad it is a good building,” explains Yoshimoto. Awarded a 4.1 out of a possible 5, the new French Embassy received an unusually high mark, especially for an office building. But top rank was not the project’s primary goal. Instead, the French Embassy is a diplomatic balance of design, comfort, and ecology that’s bound to cement the bond between the two countries.

Based in Tokyo, Naomi Pollock, AIA, is Architectural Record’s Special International Correspondent.

This article appeared in the May 2010 print issue of GreenSource Magazine.

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