The innovation project e-SAFE, funded by the EU under the H2020 Programme, is developing a new deep renovation system for non-historical re-inforced concrete (RC) framed buildings, which combines energy efficiency and improved seismic resistance. The present paper describes the main func-tionalities of a Decision Support System (e-DSS) that is being developed by e-SAFE experts, aimed at guiding the technicians and the building owners through a conscious preliminary co-design activity, and leading to the choice of the most suitable renovation solution amongst those envisaged by the e-SAFE portfolio. The e-DSS allows assessing – with a reasonable degree of approxima-tion – the energy performance of the building before and after the proposed renovation action, the environmental benefits in terms of decarbonization (i.e. reduction in CO2 emission for space heating, space cooling and DHW prepara-tion), the expected costs and time for the building renovation and the expected time of Return of the Investment (ROI), based also on the savings in the annual operating costs. The paper explains the criteria used by the tool to identify those solutions that are not suitable for the selected building, and discusses the degree of approximation behind the calculation of energy, cost and environmental per-formance.