In Italy and many European countries, deep renovation construction projects for energy and seismic building performance upgrades will be always more and more frequent, to improve sustainability and safety of the existing building stock. Energy requalification involves building envelope and MEP sub-systems, while super structure rehabilitation addresses structural sub-system and internal spaces. Therefore, the limitation of the usability of the building together with the high renovation costs often lead real estate developers and owners to choose an easier strategy, complete demolition and reconstruction of the building. Perhaps, this can be the easiest choice but, from an environmental point of view, usually the least sustainable one. Addressing environmental sustainability means measuring it, and building sustainability can be evaluated via the Life Cycle Assessment (LCA) approach, but LCA needs a complete evaluation of the existing and new building system, sub-systems and components. Therefore, a strategic choice based upon a LCA-based Decision Support System (DSS) can be performed only late in the design process, when most of the technologic systems have been designed in detail. Instead, the proposed parametric preliminary evaluation could help to choose the most environmentally sustainable design alternative earlier in the design stage, and even with a low level of knowledge of the existing building. The proposed approach uses a list of parametric costs for a building type to extract preliminary data about building quantities. Therefore, a DSS method that uses typical cost plans and existing LCA data-base is proposed to perform a preliminary LCA analysis of a building renovation project in the preliminary design stage to evaluate the sustainability of the overall strategy and of the design alternative.