More than 124 million tons of oranges are consumed in the world annually. Transformation of orange fruit generates a huge quantity of waste, largely composed of peels. Some attempts to reuse by-products derived from citrus waste have been proposed for energy production, nutrient source or pharmaceutical, food and cosmetic industries. However, their use in the building sector had not been researched. In this study, orange peels, in five different ratios, from 100% of wet peels to 75% and from 0% of dry peels to 25%, were submitted to a thermo-compression procedure. They were evaluated according to their physical (bulk density, water absorption, thickness swelling, surface soundness and thermal conductivity) and mechanical properties (bending strength and modulus of elasticity). The results showed that orange peels can be used as thermal insulation material. The addition of dried peels makes the structure of the board heterogeneous and thus increases its porosity and causes the loss of strength. Hence, the board with the sole use of wet peel, whose thermal conductivity is 0.065 W/mK while flexural strength is 0.09 MPa, is recommended.

A large share of the existing building stock in European seismic regions faces a dual critical vulnerability, namely, poor energy performance and high seismic risk, largely due to previous construction practices that ignored modern energy-efficiency standards and earthquake-resistant design. Addressing this urgent need for deep renovation, the Horizon 2020 e-SAFE project aimed to develop innovative retrofit technologies for reinforced concrete-framed buildings that synergistically achieve earthquake safety, energy saving, architectural renewal, economic feasibility, and social welfare. The e-SAFE solutions feature an integrated approach combining novel envelope technologies (prefabricated timber-based panels and three-dimensional steel trusses) and high-performance thermal systems for domestic hot water, space heating, and space cooling. This paper outlines the main multidisciplinary research methodologies—integrating theoretical and experimental investigation, numerical modeling, industrial prototyping, and participatory design—that guided the design and development of these technologies. The full e-SAFE package was subsequently applied to three diverse pilot buildings in Italy and Romania for comprehensive demonstration and validation; the paper discusses the full-scale results, including the validation of structural and energy performance, the effectiveness of the construction process, and the lessons learned from the demonstration activities. These findings highlight both the significant potential of the integrated retrofit package and specific constructive and operational limitations encountered, thereby providing critical data to inform future research and standardization efforts in integrated seismic-energy building renovation.