Phare Tower



Synthesizing Idiosyncrasies to Mend a Site

Drawing on the power of parametric scripting, the design of the Phare Tower gathers disparate programmatic, physical, and infrastructural elements from the requirements of the building and its surrounding context, and synthesizes these into a form that seamlessly integrates the building into the idiosyncrasies of its site while expressing multiple flows of movement. In the spirit of the Paris Exposition competition proposals, the tower embodies state-of-the-art technological advances to become a cultural landmark.

The complex structure and skin adapt to the tower’s nonstandard form while simultaneously responding to a range of complex, and often competing, physical and environmental considerations. Technologies integrated into the Phare Tower capture the wind for the production of energy and selectively minimize solar gain while maximizing glare-free daylight. Its high-performance skin transforms with changes in light, becoming opaque, translucent, or transparent from different angles and vantage points.

Posted: Feb 22nd, 2009 / Last Edited: Apr 1st, 2012 Print

Description

  • Between 1958 and 1989, high-rise buildings (banned in the historic center of Paris) were constructed just outside the city boundary, forming the business district of La Défense two miles west of Paris. The Phare Tower (phare being French for beacon or lighthouse) marks the first stage of a major redevelopment of the district. La Défense is currently a zone of discrete, isolated buildings amid blank plazas—essentially a nonsite.

    The tower emerges from its irregular site, defined by a neighboring motorway and a rail link, and bisected by an existing pedestrian walkway. It is located between the 1989 Grande Arche de la Défense and the 1958 CNIT building, the former exhibition hall of the National Inter-University Consortium for Telecommunications, with an architecturally significant glass façade, designed by Jean Prouvé. These disparate elements, crowded together and seemingly unrelated, provide an opportunity to mend the site. The site strategy thus synthesizes the programmatic, physical, and infrastructural complexities to connect the surrounding urban space and create a coherent sense of place where none previously existed.

    At the levels of urbanism and circulation, the scheme complements existing plans to transform the CNIT into a center for commerce and recreation. Circulation is directed from the existing transit hub below grade, through the renovated CNIT facilities, and into the tower’s public spaces via a pavilion. The pavilion connects to the Place Carpeaux, and transitions from horizontal to vertical, becoming an integral element in the tower’s form. Glazed exterior escalators soar 35 meters from the pavilion to the tower’s ninth-floor lobby, transporting approximately eight thousand pedestrians each day. As the visitor rides up the escalators to the Grand Hall, the fully glazed envelope reveals views of the traffic passing underneath, as well as of Parisian monuments in the distance.


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  • Between 1958 and 1989, high-rise buildings (banned in the historic center of Paris) were constructed just outside the city boundary, forming the business district of La Défense two miles west of Paris. The Phare Tower (phare being French for beacon or lighthouse) marks the first stage of a major redevelopment of the district. La Défense is currently a zone of discrete, isolated buildings amid blank plazas—essentially a nonsite.

    The tower emerges from its irregular site, defined by a neighboring motorway and a rail link, and bisected by an existing pedestrian walkway. It is located between the 1989 Grande Arche de la Défense and the 1958 CNIT building, the former exhibition hall of the National Inter-University Consortium for Telecommunications, with an architecturally significant glass façade, designed by Jean Prouvé. These disparate elements, crowded together and seemingly unrelated, provide an opportunity to mend the site. The site strategy thus synthesizes the programmatic, physical, and infrastructural complexities to connect the surrounding urban space and create a coherent sense of place where none previously existed.

    At the levels of urbanism and circulation, the scheme complements existing plans to transform the CNIT into a center for commerce and recreation. Circulation is directed from the existing transit hub below grade, through the renovated CNIT facilities, and into the tower’s public spaces via a pavilion. The pavilion connects to the Place Carpeaux, and transitions from horizontal to vertical, becoming an integral element in the tower’s form. Glazed exterior escalators soar 35 meters from the pavilion to the tower’s ninth-floor lobby, transporting approximately eight thousand pedestrians each day. As the visitor rides up the escalators to the Grand Hall, the fully glazed envelope reveals views of the traffic passing underneath, as well as of Parisian monuments in the distance.

    Rather than an isolated and autonomous tower, the building is a hybrid structure. The 300-meter tower straddles the site to meet the ground as a tripod. It comprises one splayed structural leg, two occupiable legs (the Trapezium, to the west, and the East Building), as well as a pavilion that engages the surrounding context and transforms the public space of the plaza. The two occupiable legs frame a 24-meter-wide by-28-meter-tall void in the tower’s base, creating a monumental urban gateway, which maintains view corridors toward the CNIT and toward Courbevoie and allows pedestrian traffic to flow directly underneath the building.

    As it rises from its tripod base, the tower’s asymmetric profile swells slightly to accommodate the soaring Grand Hall, then becomes more slender in response to wind load, and finally tapers off to a thicket of wind turbines, antennas and hair-like structures on the roof. The tower appears to shift continually, distinct from different vantage points—not a single image but a dynamic structure that responds to its site, environment, and performance requirements. At its base, the building’s skin opens, exposing a 250-foot-high Grand Hall. The Grand Hall becomes the center for all vertical transportation. From the Hall’s security checkpoint, people transition to double-deck banks of express elevators serving the office tower. On the 66th floor, a sky restaurant and a panoramic terrace, offering spectacular 270-degree views, are open to the public. Overall, the project comprises 146 988m2 or 1 582 166 ft2 of net surface area and 164 185 m2 or 1 767 273 ft2 of gross surface area.

    Technologies integrated into the Phare Tower harness the wind for the production of energy and selectively minimize solar gain while maximizing glare-free daylight. The tower is crowned with a cluster of antennas and a wind farm of turbines that harvest energy—a metaphorical garden in the sky. Both the form and the orientation of the building respond to the path of the sun. The planar, clear-glazed north façade maximizes interior exposure to year-round natural daylight. A curvilinear second skin of diagonal stainless steel mesh panels wraps the tower’s continuous south, east, and west glazed façades to minimize heat gain and glare and maximize energy efficiency.


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Sustainability

  • Optimized skin
    Both the form and the orientation of the building respond to the path of the sun; the south façade’s curvilinear double skin minimizes heat gain and glare, while the flat, clear-glazed north façade maximizes interior exposures to year-round natural daylight. A brise soleil wraps the tower’s continuous South, East, and West glazed façades. This double-membrane façade system improves both energy efficiency and worker comfort, by reducing the solar heat gain and minimizing glare, while maintaining panoramic views and affording natural light to the office spaces.

    Curvilinear south façade Flat, clear glazed north façade


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  • Optimized skin
    Both the form and the orientation of the building respond to the path of the sun; the south façade’s curvilinear double skin minimizes heat gain and glare, while the flat, clear-glazed north façade maximizes interior exposures to year-round natural daylight. A brise soleil wraps the tower’s continuous South, East, and West glazed façades. This double-membrane façade system improves both energy efficiency and worker comfort, by reducing the solar heat gain and minimizing glare, while maintaining panoramic views and affording natural light to the office spaces.

    Curvilinear south façade Flat, clear glazed north façade


    Traditionally, for optimal sun shading, brise soleil louvers are angled perpendicular to the direction of the sun’s path, as calculated on the summer solstice. Yet the complexity of the tower’s curving east-, west-, and south-facing facades, combined with the diagonal orientation of the panels, requires a unique angle for each of the five thousand stainless steel mesh panels to achieve optimal sun shading.

    Diagram of optimized skin


    Roof wind farm
    Atop the tower, the diagrid structure dissolves into spires of helical vertical-axis wind turbines. This powerful statement of environmental responsibility literally crowns the building. The natural wind energy harnessed by the turbines will provide power for the general services of the upper floors of the tower. This visually distinctive wind farm provides clean, alternative energy.

    Aerodynamic form
    The structure is an efficient hybrid concrete and steel system. The concrete core sustains a vertical load only, and the steel beams and diagrid are the ideal shape to withstand windload, resulting in material saving and a reduction in building weight. The steel diagrid structural system results in a lighter building, which facilitates the placement of such a tall tower on a small site with low bearing capacity, where a heavier building made of concrete might prove challenging.


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Details

Location:
La Defense, France
Client:
SCI CNIT DEVELOPPEMENT
Site Area:
0.8 acres / 0.3 hectares
Size:
1,767,273 gross sq ft / 164,180 gross sq m
Program:
Commercial office tower with office space, employee restaurants, public cafés and amenities, panoramic restaurant
Design:
2006 - 2010
Construction:
2013 - 2017
Type:
  • Commercial

Project Credits

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Construction Manager
Consulting Architect
Energy Modeling
Facade Consultant
HVAC and Environmental Engineer
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