GA Smart Building delivers the CNES headquarters in the heart of Paris – Les Halles

Built in the 1980s, this 9,200 m² building, owned by Gecina, underwent a full interior and exterior renovation as part of a public design-build contract awarded to a consortium led by GA Smart Building, alongside SK&Associés Architectes, engineering firm Artelia, and acoustics specialist Gamba.

A major heavy renovation project in the heart of the city

CNES, a key player in French space policy since 1961, has occupied its current headquarters for more than 40 years. Located on Place Maurice-Quentin in the Les Halles district of Paris, close to the Forum des Halles and Saint-Eustache Church, the building benefits from a central location in the heart of the 1st arrondissement. The site hosts CNES management and coordination functions alongside its centers in Toulouse, Kourou, and Paris-Daumesnil.

As part of a lease of more than 20 years signed with Gecina, the public institution, tenant of its headquarters, launched a complete modernization of the building to adapt its spaces to contemporary uses and significantly improve its energy performance.

An open, bright and reorganized building

The renovation addressed both the exterior envelope and the interior spaces.

Outside, the stone façade and original architectural detailing were preserved and cleaned. The forecourt, curtain wall, and building entrances were completely redesigned to improve the building’s visibility in the public space.

Inside, the layout was thoroughly transformed:

• Modernization of the entrance hall with illuminated wall and ceiling features inspired by the space universe
• Reorganization around a central patio to bring natural light and spatial openness
• Redevelopment of the first-floor cafeteria connected to the patio and designed as a meeting space for occupants
• Opening up of the upper floors to create contemporary office spaces equipped with modular glass partitions that promote transparency and flexibility

The rooftop terrace was transformed into a landscaped rooftop garden of 700 m². This new space is also intended to promote urban biodiversity.

The space occupied by CNES has been significantly optimized: teams are now grouped on the two upper floors (3,000 m²), while the lower levels accommodate other public organizations or entities linked to space activities.

A specific construction phasing strategy was implemented to allow the shops located on the ground floor to remain operational throughout the duration of the works.

Enhanced environmental performance

Like all GA Smart Building projects, the renovation of the historic CNES headquarters aimed for strong environmental performance. The project targeted the HQE Bâtiment Rénovation V1 certification at the “Excellent” level. The renovation significantly improved the building’s energy performance through:

• Internal insulation and replacement of windows and joinery
• Installation of energy-efficient technical systems
• Optimized resource management, use of ecological materials, implementation of materials with FDES rated A or A+, and use of products from the circular economy

As a result, the building will comply with the objectives of the French tertiary decree, helping control operating costs for CNES.

The building’s technical management was handled by Equilab, a subsidiary of GA Smart Building, through the deployment of a Building Management System (BMS) integrating a 3D BIM digital model. This system allows supervision of the building’s installations and long-term monitoring. Equilab also implemented regulation of the heating, ventilation, and air conditioning (HVAC) systems, contributing to sustainable control of energy consumption.

Thanks to full control of all renovation phases, GA Smart Building delivered this major renovation in just 18 months after the start of works, in line with the initial schedule.