On life cycle assessment in the built environmentfrom conventional sustainability to regeneration and glocal architecture

Résumé

The overarching idea of this thesis is to analyze the role of Life Cycle Assessment (LCA) as a project decision-making tool. LCA is a methodology to conduct a sustainability analysis of any human activity. This work is constructed in three levels, the study of building materials individually, the constructions, such as façades and partitions, and finally, the whole building. As the chapters progress, the focus of the study zooms out from the particularities associated with materials until arriving at the study of the life cycle of buildings. Chapter one corresponds with the first level. In this chapter, several composite boards with bio-epoxy resin and natural fibers are compared to plasterboard in terms of their environmental impact and mechanic characteristics. In the case of constructions, this thesis analyzes some important aspects related to their performance, such as acoustic and thermal insulation. Without at least a competent performance in those parameters, constructions composed of new sustainable materials cannot be considered alternatives to the conventional solutions. In chapter 2, several partition typologies combining the biocomposites and new and conventional acoustic absorbents are compared in terms of their environmental impacts and their airborne acoustic insulation. The third chapter, which also deals with constructions, analyzes the use of façade panels built using rice straw waste from the Albufera park in Valencia and compares it to the most common façade typology in Valencia, the double-layered brick wall. The study assesses the airborne acoustic insulation and the thermal transmittance of the straw construction experimentally. The hygrothermal performance of this material is also analyzed. The last chapter deals with the environmental impacts of buildings as a whole by comparing a European reference wood house in different locations in Europe. The environmental impacts of this house are studied over its whole life cycle in Munich, Ljubljana, Portorož, Madrid, and Valencia to understand how barriers towards regenerative sustainability change depending on location. When it comes to the results, the first chapter indicates that the bio-epoxy composites proposed can be a sustainable alternative to plasterboard by reducing the environmental impact by around 50%. The second chapter shows that replacing the plasterboard and the mineral wool in a drywall partition with the bio-composites and a sheep wool acoustic absorbent can reduce carbon emissions by almost 60%. The third chapter highlights the importance of finding ways of using the rice straw from the Albufera park as a raw material. Moreover, the rice straw façade analyzed demonstrated to be not only beneficial for the environment (avoids the emission of 52 kg of CO2e to the atmosphere per square meter), but also perfectly adequate to be a sustainable alternative to the most common façade typologies in Valencia in terms of acoustic, thermal and hygrothermal performance. Because of the environmental benefits of its use and the fact that it is a proximity material, the rice straw façade panels can be considered a glocal material. The last chapter shows that conventional sustainability measures, such as a wooden frame and high thermal insulation, are not enough to successfully build neither regenerative nor Nearly Zero Emissions Buildings (NZEB). The use of bio-based materials, designing towards passive efficiency, and new technologies are necessary to reach regenerative sustainability. Overall, the results emphasize the need to use LCA as a decision-making tool during the project stage of a building. LCA is the only tool that can provide an accurate representation of the influence a building will have on the environment over its lifespan.