peer reviewedIn the next decades, most of the energy consumption of the building sector in Europe will be due to the buildings that exist today. The present paper presents the first results obtained by a web-based tool developed to enable a clear visualisation of existing dwelling stock in Brussels Capital Region and to help major stakeholders and public institutions of the region to define their strategies to retrofit the dwellings built before 1945. The tool is structured with six different scales and the characterisation of building stock is based on a set of criteria focused on three main topics: energy, environment and heritage value. Existing dwellings are grouped in seven different types and each type can be retrofitted in a specific manner (envelope, systems and number of dwellings per building). This paper presents and compares five scenarios of evolution of the dwelling stock. This tool can only be used to analyse Brussels Capital Region for the moment, but the methodology can be applied to other regions in the world. Enlarging the scope of this tool will help to meet the environmental, social and economic challenges of the contemporary world and to foster the transition of building sector towards a sustainable development