In an international context that is faced with several environmental issues, especially in relation to energy efficiency, the finding of sustainable solutions for retrofitting existing buildings is a challenging issue. Comprehensive evaluation of the applied materials is required to understand their true impact on the environment as well as their economic suitability. Therefore, a life cycle-based approach is required. This work presents a hybrid method, including energy and comfort optimization, Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) analysis, applied for retrofitting a traditional rural building and then combined together in a multi-criteria approach. The case study considers the assessment of the sustainability of several solutions for roof insulation according to seven criteria derived from the hybrid method developed: energy saving, non-renewable energy, comfort performance, global warming, ozone layer depletion, respiratory inorganics and Net Present Value. The multi-criteria approach used to combine these criteria is the Electre TRI-rC method. The results obtained with this method show the division of the materials into three categories with overall bad, medium or good performance. The stability of results is verified against a two-fold sensitivity analysis. (C) 2018 Elsevier B.V. All rights reserved.