One of Europe’s largest energy consumption sources, the building sector is a focus area in the European Commission’s plans for energy efficiency improvement and greenhouse gas emissions reductions. Although legislative instruments already target new buildings’ sustainability, older buildings represent the biggest share of Europe’s stock and should be renovated to effectively reduce emissions in the sector. In Portugal, about 70% of the buildings were constructed before the implementation of energy performance regulations in 1990 and are not energy efficient. The enforced remote routine from the Covid-19 crisis evidenced thermal insulation issues and emphasized residential energy poverty (EP) conditions of the Portuguese population. Building owners can be key actors in the improvement of the national buildings stock’s energy efficiency and should be included in the buildings’ renovation process. Nevertheless, the great diversity of characteristics observed in the country’s residential buildings can be a roadblock in assessing and providing information about the different dwelling types. A bottom-up approach through the development of representative buildings typologies can be an optimizing tool in the building renovation aiming for energy efficiency improvement, enabling the proposal of sustainable retrofitting solutions for residential buildings on a larger scale. Therefore, this dissertation performs a cross-country assessment on the Portuguese residential buildings stock towards the definition of national representative typologies. A set of key building characteristics (e.g., area, floors, bearing structure) from the 2011 Census is used to identify predominant structural and architectural characteristics in the country’s residential buildings’ stock. Sub-regions’ Energy Poverty Vulnerability Index (EPVI) results and climatic zones guide the identification of priority statistical subsections for residential renovation. Sub-regions’ Energy Performance Certificates and subsections’ street view images are also used to assess residential buildings’ predominant constructive solutions and most distinctive visual elements. The most distinct building characteristics of the sub-regions were considered in the typologies’ 3D models construction in SketchUp. The results revealed Alentejo as the most distinct region regarding housing type and building’s bearing structure. Açores, Madeira, Norte and Alentejo are the regions with the highest percentage of sub-regions raking top five in vulnerability to EP. Tâmega e Sousa, Madeira and Baixo Alentejo are the most representative sub-regions in the rank from different climatic zones. Key-feature tables gathering the various regions’ residential buildings most distinct visual elements for all primary architectural components (roof, storeys, openings, envelope, access, plot) helped select examples of buildings used as a reference in the construction of the 3D models. The main differences observed in the three typologies regards the presence of sub-levels (underground floor), façade ornaments and structures, main accesses, number of openings, and plot (land lot) placement. Baixo Alentejo stands out for its typology's lack of setbacks, with few openings, and façade ornaments; Madeira’s most distinct visual element is the presence of an entry porch in its typology’s main entrance; and Tâmega’s typology is the only one with underground level and veranda, with a single flight of stairs and landing marking the main entrance. The typologies resulting from this work can be optimizing tools for residential energy efficiency renovation in sub-regions with vulnerable buildings stock, helping determine sources of energy inefficiency through the estimative of the baseline energy demand of existing buildings, allowing the proposal of adequate alleviation measures, and assisting with the integration of their owners as indispensable stakeholders on a large-scale intervention.