As a measurement, built density (coefficient of land surface to be built and total floor space) has been the object of numerous researches on urban morphology and architectural forms during the twentieth century. However, for the last ten years, its sensory and qualitative dimension seems to be particularly valued: the perceived density. In multi-unit housing, dense, innovating and compact forms show a significant change of architectural and urban conception. In fact, project practices seem to have been marked by three major changes. Firstly, the importance of the precept of sustainable development, attempting at reducing urban sprawl. Secondly, the increased interest in urban values and the idea of "building a city within a city". Lastly, the current asserted need to redefine density: on one hand, new means are being researched to control it, on the other hand there is a widening of its definition due to the main impulse of architects and researchers. Within this framework, it is illuminating to reconsider the multiple disciplines using this term, as well as the distinct spatial scales tackled in this notion and changes in its use through time. However, focusing only on built density, the present research concentrates on the architectural and urban framework, also known as physical density. It is measured by a density figure but is also qualified by the perception of density. We propose as preliminary approach, an examination of this perceived density in fields where it is more frequently used, such as literature, painting and music. Another important notion of this research requires definition: architectural and urban innovation. Standing out from pure invention, this type of innovation consists essentially in a reinterpretation of previous architectural and urban productions worth naming "retro-innovation". Despite a housing program dependent on past models reluctant to rapid and important changes, radical innovations do occur, though more seldomly. Several ''moments'' of the collective housing architectural history allow for an updating of the different stakes manifested in the density – innovation relationship. Density perception plays a large role in a particular problem emerging from these two notions in contemporary Switzerland. The issue is how encouraging people coming back to the urban centers by proposing larger apartments with more square meters and urban architecture composed of numerous and various spaces, but protecting them at the same time from too close a proximity between neighboring housing and from environmental nuisances. The state of the art brings to light the enormous influence of the researcher and anthropologist Amos Rapoport on perceived density starting with his article, "Towards a Redefinition of Density", published in 1975. For more than thirty years now, architects, psychologists, city planners and geographers refer to this work when defining this notion in their respective fields. As a consequence, it nourishes s
Marine Françoise Jeannine Villaret