Skyscrapers or glass towers are an extremely common model throughout the world. In the current context of climate change and resource depletion, we need to develop new postures towards these objects, especially for existing buildings that are becoming obsolete. This article begins by showing how the nature of the facades of these buildings influences the urban climate. It continues with the analysis of an emblematic building from the 1970s, the Tour Areva in Paris-La Défense (France). Through this typical example, we show how it is possible to improve the quality of use and the energy performance by exploring various scenarios. The main theme is the transformation of the façade and how it is possible, through different actions, to simultaneously improve daylighting performance, visual and thermal comfort and overall energy performance. New approaches to geometry and photometry are explored and show, through daylighting and thermal simulations, that it is possible to give these objects a new start. This work concludes with a life cycle analysis that quantifies the valorization of the intrinsic energy stock associated with the building and which elements can be conserved or reused. In this project, we demonstrate that with good design, it is possible to convert these office buildings into pleasant and generous flats and to achieve a high level of energy efficiency and comfort, without forgetting the environmental objectives for the 2050 horizon.