DOI: 10.7764/RDLC.16.1.22At present, architects and engineers design in such a way that their projects comply with the local regulations of the place where they are working. However these local rules are not enough to achieve the sustainability objectives set by the European Union for 2020. The selection of one building material or another will establish, in part, the building's global environmental impact. For this reason it is increasingly necessary to characterize, on an environmental level, building materials, in order to be able to prescribe the most suitable material to incorporate to architectural projects. Taking into account that thermal insulation materials are one of the key elements in construction, since they help the building's energy saving, the environmental impact of extruded polystyrene, glass wool and cork are assessed in this article in a comparative manner, by the Life Cycle Analysis (LCA) methodology. In conclusion, according to the results obtained, there is not one best product, environmentally speaking, for all the impact categories analyzed. The choice of a material or another must be done adopting a solution of global commitment, cork being the best material out of the ones selected.