Cities have a key role in achieving the 2030 EU environmental, energy, and climate targets, in particular the residential building sector, which is the major source of energy consumption in urban areas. The Italian building stock is composed of over 50% of buildings built between the '50s and '80s, which have obsolete thermal system technologies and inefficient envelopes. Urban energy planning should be used as a resource to highlight the major criticalities in existing buildings and to correctly identify the strategies to adopt. This thesis work analyzes residential buildings of Milan to evaluate actual heating energy consumption and their possible reduction due to different retrofit actions.