Life Cycle Assessment for Climate emergency: A Multiscale Analysis of the Environmental Quality of Buildings in a subtropical island environment

Environmental impacts from anthropogenic activities remain significantly present in the atmosphere. A large part of these environmental impacts is attributable to the construction sector. This thesis was developed in the context of the ecological transition at the scale of Reunion Island. The objective of this work is to understand the factors of the environmental quality of buildings in an insular subtropical environment and to propose alternative approaches to these assessments. The environmental performance of buildings can allow a significant reduction of greenhouse gas (GHG) emissions at both structural and functional scales. In this thesis, a first evaluation of the environmental impacts of the built single-family houses (SFH) allowed us to identify and define the total ratios while considering the representative share of the structural, functional, and end-of-life scales. For this, it was necessary to build a regional database that regionalizes the emission factors (EF) specific to the island. This holistic approach allowed us to highlight the environmental over cost of the island due to its geographical location. Furthermore, we considered another constraint: the impact of the local electricity production mix, which contributes strongly to the operational phase. For this purpose, a prospective approach was carried out through decarbonization scenarios and allowed to determine the decrease of the impact of local electricity generation for the next to 2040, thanks to the integration of new technologies. Finally, the local database having been primarily developed, two approaches, 'simplified' and 'synthesized', were proposed: the simplified approach was initiated to make LCA affordable to professionals so that they have simplified tools for evaluating their projects. Then, the synthesized approach (ICE) allowed us to simplify the information and propose an impact threshold applicable to the constructions in an insular environment. Finally, given all these works, we bring to the first light the importance of integrating a new paradigm of building sustainability. This definition must incorporate the capacity of the building recycling capacity. But it must be considered a short economic chain of revalorization at the scale of India-Oceania. (author)