In this paper, an integrated approach targeting sustainability, safety and resilience is envisioned for the renovation of the post-Second World War RC buildings clustered in urban outskirts. The solution stems as an enhancement of the widespread camouflage practice, which targets energy efficiency and architectural restyling by complementing the building with a technological double skin, self-supported on an independent exoskeleton. Based on this integrated approach, the exoskeleton can be further engineered to also enable structural safety and resilience. Life cycle thinking is addressed to re-conceive traditional structural design approaches, guaranteeing safety, while minimising costs and environmental impacts over the building life cycle. Accurate selection of materials and dry technologies enables adaptability, reparability and maintenance, and total recyclability/reuse at end-of-life. The intervention is carried out from outside, avoiding relocation of the inhabitants and possible building downtime. The paper introduces a possible framework for engineers, technologists and architects to design new holistic renovation interventions, for which innovative solution sets are required. Possible structural techniques to be coupled with energy refurbishment are proposed. As a proof of concept, the envisaged holistic renovation strategy is applied to a reference building, and benefits entailed in combining structural safety measures within an integrated intervention are commented.

The decarbonization of the construction sector, which is one of the most impactful sectors worldwide, requires a significant paradigm shift from a linear economy to a circular, future-proofed and sustainable economy. In this transition, the role of designers and structural engineers becomes pivotal, and new design objectives and principles inspired by Life Cycle Thinking (LCT) should be defined and included from the early stages of the design process to allow for a truly sustainable renovation of the built environment. In this paper, an overview of LCT-based objectives and principles is provided, critically analyzing the current state of the art of sustainability and circularity in the construction sector. The effectiveness of applying such design principles from the early stages of the design of retrofit interventions is then demonstrated with reference to a case study building. Four seismic retrofit alternatives made of timber, steel and concrete, conceived according to either LCT principles or traditional, were designed and compared to a demolition and reconstruction scenario on the basis of five common environmental impact indicators. The indicators were calculated adopting simplified LCA analyses based on Environmental Product Declarations (EPDs), considering the product and End of Life stages of the building. The results of the comparative analyses confirm that LCT-based retrofit solutions are less impactful than both the traditional seismic retrofit interventions and the demolition and reconstruction scenario.

The European goal to reach carbon neutrality in 2050 has further put the focus on the construction sector, which is responsible for great impacts on the environment, and new sustainable solutions to renovate the existing building stock are currently under development. In this paper, the AdESA (Adeguamento Energetico Sismico ed Architettonico, in Italian) system, a holistic retrofit technique for the integrated renovation of the existing buildings, is presented. The system was developed by a consortium of enterprises and universities and was applied to a pilot building. The system consists of a dry, modular and flexible shell exoskeleton technique that implements different layers depending on the building retrofit needs (cross-laminated timber (CLT) panels for the structural retrofit, thermal insulation panels for the energy efficiency amelioration, and claddings for the architectural restyling). In order to foster actual sustainability, the solution contextually targets eco-efficiency, safety and resilience. To this end, the system not only couples the structural and energy interventions to reduce the operating costs, but it is also conceived in compliance with life cycle thinking (LCT) principles to reduce impacts throughout the remaining building service life (from retrofit time to the end of its life). The system is designed to be easily mountable and demountable to allow for the reuse/recycling of its components at the end of life by adopting macro-prefabricated dry components and standardized connections, to reduce damage caused by earthquakes by reducing the allowed inter-story drift, and by amassing the possible damage into sacrificial replaceable elements. The paper describes the AdESA system from a multidisciplinary perspective and its effective application for the deep renovation of an existing gymnasium hall.

Existing buildings can reach a performance enhancement and extend their nominal service life through renovation measures such as seismic rehabilitation. In particular, when buildings have almost exhausted their service life, seeking an optimal solution should consider whether costs and environmental effects are worthwhile, or new construction is preferred. In this paper, a methodology to consider seismic hazard into probabilistic approaches for life-cycle analyses is presented considering the possibility of structural enhancement over an extended building lifespan. A life-cycle-based decision support tool for building renovation measures is developed and applied to a selected case study. Unlike standard “static” analyses, which in this work show shortcomings by underestimating impacts of vulnerable buildings, such an approach brings out environmental and economic advantages of retrofit measures designed to improve the structural performance.

Given the current climate emergency and the ambitious targets of carbon emissions reduction, retrofitting strategies on existing buildings typically include reducing energy demand, decarbonising the power supply, and addressing embodied carbon stored in materials. This latter point redefines the role of engineers in the transitions towards a sustainable construction sector, being they responsible for designing low impact, sustainable and carbon neutral solutions. A Life Cycle Structural Engineering (LCSE) approach, inspired by the principles of Life Cycle Thinking (LCT), should thus be adopted for the sustainable renovation of existing buildings. Only recently have pioneering approaches been proposed, tackling multifaceted buildings’ needs, such as those related to energy consumption as well as seismic safety, but often disregarding LCT principles. This study presents a redefinition of the concept of LCSE for sustainable construction and a comprehensive review of available methods and tools to operationalise the LCSE approach in practice, focusing on the consideration of LCT principles in the retrofitting design process, integration of seismic loss estimation and environmental impact assessment, and implementation of integrated retrofitting strategies. The greatest ambition of this work is thus to boost a paradigm shift for building engineers towards an interdisciplinary perspective in building assessment and retrofitting.