A framework for the sustainable renovation of existing structures: application to a reference building

The current dramatic environmental situation has emphasized the need to introduce sustainability issues into the construction sector to substantially reduce its large environmental impacts. Such impacts are mainly connected to raw material depletion during construction/renovation works, to the energy consumption and CO2 emissions during operational phases, and to the waste disposal at the building dismissal and end-of-life. The most sustainable approach to the built environment should consider deep renovation rather than demolition-and-reconstruction, considering energy and structural upgrade of existing buildings to the modern standards, obtained through adoption of sustainable low-impact techniques. With such premises, a sustainable building renovation design (SBR-D) framework has been recently proposed by the authors, which is aimed at identifying the most sustainable retrofit option under an environmental, social, and economic point of view. The framework is inspired by sustainability principles complying with the Life Cycle Thinking approach, such as: recyclability of the materials, reusability of the components, demountability of the solution, reparability/replaceability of the construction components, cost reduction over the life cycle and so on. This comprehensive approach allows minimizing the impacts during the whole life cycle of the retrofitted building, whilst boosting the actual implementation of the retrofit interventions. The framework also encourages the adoption of holistic retrofit strategies and techniques, tackling multiple building deficiencies in a single step (energy, structural, etc.). The framework consists of 4 steps: 1- evaluation of the as-is condition of the building under a multidisciplinary point of view; 2- qualitative pre-screening of the possible retrofit solutions adopting multiple-criteria decision-making (MCDM) methods addressing environmental, social, and economic criteria; 3- design of the selected solutions with performance-based methods; 4- choice of the best retrofit option. This paper presents the framework and its application for the renovation of a reference RC building typical of the European post-WWII building stock. In Step 2, the solutions are compared adopting a Multi Criteria Decision Making method. Different scenarios are considered depending on the building constraints and on the requirements of the stakeholders, thus defining different weights for the selected criteria. The best retrofit option under an environmental, social, and economic point of view is finally determined for each scenario.