Improving energy and structural performance of existing buildings through engineered skins in deep renovation interventions

The majority of the European buildings is characterized by high energy consumption, technological obsolescence, and living discomfort. Moreover, these buildings have exhausted their structural service life (50 years) and may be structurally unsafe. In this paper, an integrated deep renovation solution for the seismic retrofitting, energy efficiency upgrade and architectural restyling of existing concrete buildings is proposed. More specifically, the performance of a technological-structural shell made of pre-fabricated, insulated panels is presented. The structural shell enforces a box-structural behavior of the existing building, while improving energy efficiency. The intervention is conceived to be entirely carried out from outside the building, without causing any disruption in the building use. The new shell can either adhere to the existing structure, as a thermal-structural coating layer, or can be located with an offset, thereby enabling remodelage interventions to include balconies or living spaces. The combined retrofitting increases the building nominal service life and, when replicated at large scale, increases the resilience at district level. The concept of Life Cycle Thinking is integrated in the design of the solution and in the selection of the technologies to maximize sustainability and resilience: the new skin is equipped with structural “fuses”, in which possible structural damage can be lumped to enable easy reparability after an earthquake; the additional structural skin is designed as fully demountable and recyclable at the end of life. Pre-fabricated technology is addressed to enable easy assemblage and to shorten the construction site and retrofit work duration, to improve reparability and adaptability over time. Furthermore, the pre-fabricated solution optimizes raw material consumption and reduces waste production during the whole building life cycle. Feasibility of the conceived integrated intervention is finally assessed with reference to a case study building, representative of the Italian building stock.