Portugal has set a high degree of ambition and determination to be at the forefront of the energy transition through a strong commitment to renewable energies, sustainability and energy efficiency. The methodology used in this dissertation to evaluate the energy efficiency potential of the residential buildings in the Alfama neighborhood,selected as a case study, is supported by the analysis of six types of representative residential buildings. In order to characterize in detail,the dwellings included in the typologies, an analysis of 4142 energy certificates from the national database of energy performance certificates (ADENE) was used. The energy needs obtained for the retrofitting scenarios were compared with those of the current situation. In scenario A, the application of measures to improve rooftop coverage allows a reduction of 29% of space heating energyneeds, 11% bywindows related measures, and 54%in walls. With regard to space cooling needs, the improvements in coverage induce a decline of 33%, of windows10% and on the walls the needs have increased by approximately 6%. When all measures were applied simultaneously, there was a 92% reduction in space heating needs and a 35% reduction in cooling needs compared to the current situation. In scenario A, the application of roofretrofitting measures is estimated at around 10.5 M€ forall typologies, windows around 67 M€ and for walls 25 M€. The application of these measures in all buildings present in Alfama, requires an investment of approximately 100 million euros.For scenario B, the application of the measures in the building stock influenced the reduction of heating needs by28% due toimproved insulation of roofs, 20% due to windows replacementand 47% due towalls. Regarding cooling needs, roof measures allows a potential decrease of 31%, but anincrease of 6% from windows and 4% fromwalls. These impact values reflect the trade-off between applications of renovation measures to improve thermal comfort during both seasons (heating and cooling). Finally, the implementation of the overall set of measures show a significant reduction,of 82% in space heating and 20% in space cooling energy needs.For this scenario, the retrofitting measures for all residential building stock in Alfama requires an investment of 45 M€ (2.9 M€ for roofs; 26 M€ for windows; and 17 M€ for walls retrofitting.