A “breathing” facade

The majority of the work relating to the environmental design concerns the envelope of the tower which, in addition to the renovation of fluids and systems, will substantially contribute to the project’s resource efficiency goals. In contrast to a new building, where the criteria of footprint and exposure can be leveraged to improve energy performance, these cannot be applied to a tower under renovation. Instead, It is the thickness of the new facade, its shape, technical detail and materiality which will deliver most of the bio-climatic performance of the project, providing more comfortable conditions to occupants and generating substantial energy savings. This high-performance facade includes within its thickness an original natural ventilation principle which can be deployed from top to bottom of the tower, augmenting the energy performance of the facades to fulfil the high standards of the project whilst modifying its occupants’ relationship with the exterior.

The design of this skin naturally requires studies, tests and detailed aeraulic simulations so as to overcome the difficulty of adapting the facade to the architectural constraints arising from the new wide glass panelling on the tower. To enable the effective, flexible and fair use of natural ventilation during long periods throughout the year, we opted for a “chequerboard” exterior facade shape which creates positive and negative pressure on either side of each facade panel, thereby creating natural air circulation between the exterior and interior of the tower. This circulation is captured by external/internal vents and ducts running across the facade, and is flow-regulated by automated shutters.