Europe’s largest law complex, the 160-meter-tall Paris Courthouse skyscraper by architectural firm Renzo Piano Building Workshop (RPBW), reunites under one roof the various activities of the French capital’s judiciary system that had previously been dispersed throughout the city due to a shortage of space in its historic seat on Île de la Cité (which continues to accommodate the Criminal Court, Court of Appeals and Supreme Court). Bringing together the regional court, police court, public prosecution courts and district courts of each arrondissement, its location on a L-shaped site beside the Martin Luther King Park and the ring road in the Clichy-Batignolles urban development zone on Paris’ northwestern edge in what was formerly an abandoned railway area places it at the crossroads of the city’s administrative districts and suburbs. It is part of a new eco-district currently under construction, which will comprise housing, offices, shops and a metro and tram station.
Under the framework of a public-private partnership, the French state delegated construction to a major investor and building company, Bouygues Bâtiment, which will remain owner of the property for 27 years before handing it over to the nation, currently a tenant on a long-term lease. The French government had initially proposed splitting the law courts into two distinct buildings – the first to house public functions, such as courtrooms, and the second, offices – but RPBW chose a single integrated edifice welcoming up to 8,800 people daily including 2,000 employees, which through its size and status would come to symbolize the point of departure for the rehabilitation and redevelopment of the Porte de Clichy neighborhood.
Having won the competition in 2011, the architects wished to set a new benchmark for energy consumption in a very tall building and to lessen the visual impact of the tower against the skyline by designing a series of four stacked glass volumes that diminish in size as they rise upwards to form a step-like profile. From the park, the courthouse blends into its surroundings as it has a slim profile, with the smallest façade oriented to the south to reduce the solar factor, while giving users the best views of Paris: the Eiffel Tower for those on the east side and Montmartre for those on the west. Every office has a window with unobstructed views as the immediate area is free of high-rise developments.
The east and west façades of the top three blocks stretch beyond the building to produce fine glass “frames” that heighten the sense of lightness. Each of the three volumes is only 22 meters deep so that natural light touches the core easily, with two vertical “spines” running up the sides of the east- and west-facing glazed façades lined with extremely visible solar panels – never done before on the façade of a high rise – which display a desire to shift toward using renewable energy in public buildings. The east side houses an external lift with panoramic views, while the west side includes balconies to insert agreeable outdoor spaces. Further promoting well-being are semi-outdoor relaxation areas like double-height winter gardens. The tower includes communal areas, a restaurant, cafeterias, a library and meeting rooms.
A heavy concrete structure as is traditional in France for a building of its size since steel production in the country has almost disappeared, the courthouse uses concrete from Lafarge Holcim’s factories based in the Paris region (Batignolles and Gennevilliers). The building’s energy performance respects the Paris Climate Plan’s goals, 2012 thermic regulation requirements and HQE certification (the French High Quality Environmental standard). With an ambitious energy consumption target of 50 kWh/sqm/year, the tower has already achieved around 70 kWh/sqm/year, which is half that of a typical high rise. Energy is recycled and energy efficiency is continuously controlled through the building management system to detect and diagnose consumption waste.
With 50,000 sqm of highly-transparent glass panels whose coating reflects 33 % of the light falling onto it (thus the sky is reflected under certain angles), RPBW had considered the glass characteristics of each façade according to its orientation to offer the best compromise between high light transmission in favour of natural light, reduced solar factor to limit solar radiation in summertime and low thermal conductivity to reduce heat loss. It chose a high-performing building envelope composed of a double-wall ventilated façade with an excellent daylight factor, meaning practically no use of electrical lighting during the daytime and remarkable insulation in winter. Automatic solar blinds descend in the sun’s presence to prevent the tower from overheating. Partner in charge, Bernard Plattner, says, “A court building is usually not visible from the outside. Our building is very transparent. The double-skin façade is an efficient way to have large openings to get maximum daylight inside. Transparency is also symbolic. That means it’s a building of justice and not a dark building that hides what is happening inside. It’s supposed to give the impression that there is a certain idea of transparency in the exercise of justice.”
The long and low ground building serves as a pedestal for the other three volumes to rest upon. Inside, the public lobby separated into three atria extending up through the full height of the pedestal (up to 27 meters) is naturally ventilated during the mid-season, as its soaring space facilitates the chimney effect with the opening of oculi in the upper part. This natural ventilation is handled automatically by the building management system thanks to temperature, wind and humidity captors, while underfloor heating and cooling ensure a comfortable year-round temperature. European wood has been used abundantly as it’s a warm material conventionally used in court buildings. The 90 courtrooms showcase parquet floors and microperforated, acoustically-absorbent steamed beechwood paneling, and have visual contact with the exterior, taking advantage of daylight entering through the façades, whereas law courts generally have no windows for privacy and discretion.
The three other blocks each encompass 10 floors of meeting rooms and offices, which are separated by landscaped roof terraces planted with 323 trees (oak, maple, hornbeam and birch). The eighth floor features a 5,650-sqm planted terrace, onto which the staff restaurant opens, intended as a dedicated space for walking, relaxing, reflecting and informal interaction between employees. Another 2,000 sqm of outdoor gardens occupy the 19th and 29th floors – currently the highest planted terrace in Paris at a height of 100 meters – enabling the Martin Luther King Park to “extend” into the building. As these terraces cover practically the entire ground surface, rainwater is absorbed and reevaporates in the space with almost none entering the sewage system.
Plattner believes that the Paris Courthouse can serve as a model for sustainable practices for other public projects worldwide, stating, “I hope it can prove that it is possible to have outdoor spaces up to 100 meters up in environmentally-friendly high-rise buildings that benefit the user. In France, high-rise buildings in the ’70s and the ’80s were basically of very poor quality, and people generally thought that they were horrible things, especially when you look in the suburbs of Paris, but I’m sure it is possible to give a signal through this building that high rises have a good future thanks to their conviviality and quality of life. I very strongly believe in the society of urbanity in which we live – it’s half of the world’s population – so we have to develop sustainable high-rise buildings of comfortable quality of life for our future.”
