Four years work and € 300 millions were needed to modernize the 155 m high tower erected in 1974. The objectives of the American KPF practice in charge of its important renovation were to significantly improve the quality of the spaces, to ennoble the building’s entrance and to create a new, strong architectural image on the Paris skyline. The design also focuses on integrating the building in the dense urban context surrounding it, improving the quality and accessibility of public areas and strengthening the connection between the building and the Grande Esplanade located at the heart of La Défense.

Initially composed of three wings, the height of the original building has been raised and the top of one of the wings has been trimmed to create ten levels. The buildings enlargement on all its facades facilitated passages between the three wings which were before separated. KPF is quite used to very high towers, for instance, the Shanghai World Financial Centre or the Hong Kong International Commerce Centre both close to 500 m high. The First Tower with its 52 floors and its extended area of 87 000 square metres, doesn’t want to compete with its Asiatic cousins. If the architects have preserved 80% of the old concrete structure, the whole building was reinforced. The design also increases the indoor environmental quality by replacing opaque gable walls by 40 000 square metres of glazed façade to bring natural daylight into office spaces and to open views out to the city. A naturally ventilated double skin wraps half of the building. “Its application is a balance between engineering constraints and the aesthetic goals of a dynamic form” added the designers. This insulation, the low emissivity glazing and all the automatically regulated equipments helped to reduce the heating needs by 80%, the air-conditioning costs by 50% and the general energy consumption fivefold. Beyond its architectural qualities, the First Tower shows exceptional ecological performances which will be a striking event in the La Défense history. First is to-day a renewal symbol and the flagship of this business area. Until the new Phare Tower (architects Thom Mayne/ Morphosis) arrives in 2016 to take the lead.

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