The ecological emergency is turning the world of architecture upside down, forcing a fundamental rethink of the design and construction methods developed throughout the twentieth century. The aim of this conference is to explore this paradigm shift, in which finite resources and demographic challenges are forcing us to reinvent architectural practices. Focusing on three themes - materials, climate and pre-existence - we will examine how the use of forgotten materials from the 20th century is forcing us to question the architectural language we can develop. Optimising sources of energy consumption in buildings also leads us to question built morphologies. Finally, the logic of not demolishing any building, whatever its heritage value, because it is in itself a source of energy that has already been consumed, also forces us to question the way in which we need to establish a relationship with what is already there in order to adapt it to today's uses and technical requirements.