Retrofit of European Residential BuildinEurope is leading the decarbonization of the building sector through directives such as the Energy performance of buildings directive (EPBD) (2010/31/EU)[3] and the Energy efficiency directive (2012/27/EU) that support the implementation of efficiency measures to achieve a highly energy-efficient and decarbonized building stock by 2050. As a consequence, Building stock modelling has become an important topic since it represents a tool able to accomplish the targets proposed in a cost-efficient way. However, the research of cost-optimal levels for an entire building stock is a complex task. Indeed, there are still limitations in the nowadays models as: (i)??They are not able to forecast what the minimum number of buildings to produce a reliable model of the stock is, allowing to decrease the computation time.