One of the oldest buildings in La Défense, Paris’s high-rise office district, is well on its way to turning into an energy-efficient entity. This will be facilitated by a highly modernised glass façade among other sustainable and Green features. This building is the “Tour First” or “AXA Tower”, re-christened as “First Tower”, and has been under renovation since 2007. Post completion of the reconstruction, it will stand as the tallest office building in France, at a height of 231 meters. It is already the first skyscraper in the country to have received a HQE (High Environmental Quality) certification.

The renovation is being driven by London-based Kohn Pedersen Fox (KPF) Associates, and execution involves incorporating 80% of the building’s original concrete structure into the revamped version. The tower is sprawled over a total floor space area of close to 87,000 square metres. The project earned the title of “Best Refurbished Office Building” at the 2011 MIPIM Awards.

Glass Façade

The advanced solar control glass that forms the façade is to play a pivotal role in determining the sustainability of the First Tower. The facade element combines a double and a single skin in a single module, while the sharp edges of the old building were rounded using curved glazing in order to impart a slender look and to make the contour more dynamic. 

Façade elements differ depending on the extent of exposure to sunlight. The outer skin of the façade, which receives greater exposure, will be mounted with SGG ANTELIO ARGENT, a solar control glazing product from Saint-Gobain Glass over approximately 17,000 square metres. This glass helps the double-skin façade achieve optimum energy balance and minimize air conditioning costs.

Low-emission windows and solar protection devices are used in the building for energy conservation. Sky gardens at First Tower serve as comfortable spaces for informal meetings and breakout areas along the building exteriors.

HQE certification
First Tower has earned a “high performance” rating in the following four HQE® evaluation categories:
1.    The building’s relationship with the immediate environment.
2.    Energy management.
3.    Building maintenance and sustainability.
4.    Occupant comfort.

Energy Management
The following techniques facilitate maintenance and enhance energy-efficiency at First Tower. 

1. Connections to the district heating and cooling networks.
2. In-house provision for heating requirements through installation of a gas-fired to reduce load on the district heating network.
3. Cooling via heat pumps to reduce demand on the district cooling system.

First Tower is a brilliant example of how an existing building can be enhanced with energy-efficient features without compromising on aesthetic and functional performances.