Towards net-zero carbon facades. (Bio)-circular strategies for Curtain Walls retrofitting

Energy retrofitting is central to achieving Europe's goal of carbon neutrality by 2050, and office buildings, responsible together with wholesale buildings for around 50% of the energy consumption of the non-residential sector, offer great potential. Their building envelopes are associated with 50-60% of total heat losses and are essential for improving energy efficiency. Since the 1980s, glazed Curtain Walls (CW), 36% of total office building envelopes, (with glass at 60% per module), have contributed to high energy dissipation while adding significant Embodied Carbon (EC) due to glass disposal at the End of Life (EoL). Considering their lifespan of 30 years and current overheating problems due to rising temperatures, CW systems require improved EoL strategies as well as enhanced energy performance, possibly without affecting their EC. In this regard, using bio-residues, absorbing carbon over growth and storing it until their EoL, offers an alternative for CWs insulation. This research combines circular and bio-economy to develop and assess a new context-based energy retrofitting strategy for CW systems, tailored to specific geographies, - Italy, Germany and Sweden, due to their different climatic conditions and office building stock potential -, related available resources and needs. In this context, it explores the integration of agro-industrial bio-residues for producing Mycelium-Based Composite (MBC) thermal insulation, alongside strategies for glass recovery and reuse from existing CW systems. Two key retrofitting scenarios are explored: (1) by mean of comparative Life Cycle Assessment (LCA), the carbon savings given by the use of an alternative CW module made of remanufactured glass and reused aluminium and steel are analyzed in comparison with a standard CW module made of virgin materials; (2) through its technological development, a new retrofitting solution, based on the indoor overcoating of a CW facade with MBC insulation, is designed, assessed and prototyped to enhance energy conservation while extending the façade service life. In this context, the thesis, adopts a multi-disciplinary and multi-scalar approach, which goes from the resource, to the material, and to the façade system scale, combining notions of architecture, energy physics and biology. By doing so, it offers insights on European office building potential and available bio-materials for construction applications, and informs on the quantitative benefits the adoption of alternative retrofitting strategies might achieve towards a net-zero built environment.