Advanced materials for the energy retrofit of opaque building envelopes. From laboratory thermal characterisation to the application on the building components

In EU almost 40% of the final energy use is consumed by the building sector. In particular, ~ 83% of existing buildings were built before 1991 when poor or no-energy regulations were applied. For this reason, pushing towards deep renovations of the existing building stock, which has an important energy saving potential, can be one of the best solutions to address the next targets of 40% reduction of the emissions until 2030 (Paris Agreement). Among the retrofit interventions, the renovation of building envelopes seems to be one of the most effective practice. Nevertheless, the intervention on building envelope presents several issues, since space saving, technological and historical compatibility represent important barriers which limit the large diffusion of envelope retrofit intervention. In the thesis four different advanced materials were deeply investigated: Super Insulating Materials, Advanced Thermal Plasters, Phase Change Materials, and Low Emittance Materials. These materials start to be attractive since they seem to be particularly suitable for all the cases in which usual envelope retrofit techniques cannot be adopted. Their high potential is mainly related to the high thermal performance (thermal insulation or storage capability) they are able to provide with lower thickness and less use of space if compared to traditional materials. Unfortunately, the building sector is a conservative market, and as a consequence, despite the great potentials of advanced materials, they are still poorly adopted, because of the high costs, the short durability (concerning the building lifetime) and the lack of knowledge about their actual thermal behaviour. The aim of the thesis is to overcome the barriers that limit the use of these advanced materials in buildings, providing methodologies, tools, data and guidelines related to their application in energy retrofit interventions on opaque building envelope components. For this reasons the research activities were focused on experimental (in lab and in-field) analyses and on numerical modelling. For each Advanced Material, the investigations were carried out at different scales: material, component and building scale. At material scale, laboratory assessment of the thermal performance and development of new testing procedures were carried out by using a Heat Flow Meter Apparatus. At building component scale, laboratory experiments using a double climatic chamber (Building Envelope Test cell) were performed. Moreover, each presented technology was installed in a real case study (demonstration buildings) and its performance was monitored under actual operating conditions. The results of the in-lab and in-field experimental activities were used for the empirical validation of different simulation software. Moreover, the validated models were used to test different design alternatives that allow defining new guidelines for the proper design of envelope retrofit making use of advanced materials. In the last phase, the analyses allowed to scale up from the component level to the building/room level, so to identify and to demonstrate the effects/benefits achievable through the adoption of the proposed advanced materials on IEQ and energy demand, in comparison to usual and conventional solutions.