The renovation of the business district received last July a new impetus under the Plan of renewal of Defense announced by the state. The construction of new towers is the showcase for this project. To ensure the good graces of the authorities, the architects is the greater part ecology. But at what price?

Project Features of Defense, the lighthouse tower architect Thom Mayne was chosen a November 27 last al'issu of international consultation. The jury in its public part by the EPAD and Unibail, the owners, therefore upheld the project of the American agency Morphosis. "Not since Mitterrand to find an architectural project of this ambition," told Reuters Leon Bressler, a former CEO of Unibail and chairman of the panel, on the sidelines of a press conference to present the project.

But at a cost of 800 to 900 million euros, this site is worth, equivalent to the François Mitterrand Library, which has twice the acreage. The other candidates (1) in the competition, have presented high quality projects around 450 million euros.

Leaving aside the aesthetic daring of the tower Phare appreciate that everyone according to his own subjectivity, it should try to understand what motivated Unibail meadows to pay twice to build this building, and to endorse this EPAD project.

From the side of the state, where Dominique Perben, Transportation Minister, announced the establishment of a new tower "characterized by its architectural and daring to be innovative and not necessarily by its height. First round, which will use all the techniques of sustainable development It must become a symbol of the revival of La Défense as CNIT or the Grande Arche have marked other stages of the site ", it was may be to give new impetus face al'attraction exercised by the British Capital. Indeed for Paris, the competition is tough. Of the ten groups worldwide located in Defence in 1995, seven are now ten years later. Over the past five years, London has attracted a quarter of new headquarters and service platforms in Europe, compared to only 5% for the Ile-de-France. "Defense is delayed and requires new and ambitious projects to maintain its status and boost its image," the worried Épad in July.

For Unibail, this construction allows the french first owner of commercial real estate to consolidate its leadership position. "Our commitment to this project is highly symbolic, was to confer upon it an architecture resolutely break and turning it into a model of sustainable development by relying on the latest research in the field of new technologies," says Guillaume, for its part, Poitrinal, CEO of Unibail. More ecological, highest, most unusual and most expensive towers of Defence, this project Phare (originally called turn signal) therefore aims to reinforce the control of Unibail illuminant in the business district. Asked prestige.

The ecology is not the only criterion in this case. Already under construction in the defence, two other equally innovative tours have indeed received the CSTB (scientific and technical centre of the building) certification High Environmental Quality: Generali tour of the agency as an architect Valode and Pistre built by real estate VINCI , and the tower of the Granite Societe Generale de architect Christian de Portzamparc. Also competing projects presented to Unibail also contained an ecological dimension.

Thus in order to remain competitive, architects must take into account the environmental factor. Mecaniquement, the introduction of this size leads to a surcharge of 10% to 20%. Factor saving energy, strength against international competition, sustainable development is therefore in line with the policy of urbanism. But let us not be naive, other criteria to guide sustainable choices, the Lighthouse tower is a case in point. The promotion of Ecology also requires an understanding of these realities.

(1) Norman Foster, Jacques Ferrier, Massimiliano Fuksas, Manuelle Gautrand, Herzog and de Meuron, Rem Koolhaas, Nicolas Michelin, Jean Nouvel and Dominique Perrault