Le mur à haute performance thermique : évolution et perspectives de la façade porteuse en béton préfabriqué à Genève dès 1973

The scope of this research includes the development of composite concrete façade elements that are thin, loadbearing and of high thermal performance. The research applies to manufactured precast concrete elements and focuses on improving their structure in terms of their construction but also their cost and environmental impact. During the last four decades, society’s energy efficiency awareness has been steadily growing in everyday life and in scientific circles. The Swiss Federal Institutes of Technology are promoting a plan known as the 2000 Watt Society (Société à 2000 Watts) which would reduce the energy consumption of the country’s inhabitants. In the context of Swiss construction, Minergie type labels are a requirement ensuring improved living conditions at lower energy consumption levels. These new ambitions increase the thermal requirements which in turn lead to the inevitable thickening of the building envelope. In a Swiss urban context, such as the Geneva region in particular, land is increasingly rare and the price of leasable surface continues to rise. As a result, the materials commonly used for insulation are economical but bulky ; they increase the thickness of the façades and significantly reduce the usable surface available for buildings. In an urban context such as this, what is the suitable dimension and fair price of a wall ? The method used was to analyze the strategies that would result in the correct dimensions of high thermal performance walls. Diminishing their width increases the area of livable surface while maintaining the wall’s thermal, static and sustainable standards. The objective was to establish a process for determining the composition of products that carry the Minergie-P and Minergie-Eco label. To this end, several tests and a pilot project for an individual house were carried out using optimum high thermal performance precast concrete walls as a model. The test demonstrated the feasibility of this type of wall. The innovation was to place between the two layers of concrete, a high thermal performance Vacuum Insulated Panel (VIP) type material and a traditional one. This combination allowed optimizing the thickness of the wall while responding to construction constraints. The proportion of the combination of insulation materials was selected according to their thermal performance, environmental impact and price. The goal was to maintain a constant thickness from the stages of project design to its completion. The argument of this dissertation is based on the conviction and the importance to commit to the use of high thermal performance construction materials overall in the future. At present, in the midst of a fossil fuel crisis, this is no longer just an individual concern. Indeed, the scarcity of fossil fuels and global warming are vital and critical problems that can be solved by using appropriate architecture solutions such as heat traps.