European directives and the objectives of the continent's 2020 strategy identify an urgent need to rehabilitate inefficient urban environments and bring them in line with a twenty-first century social market economy based on low carbon emissions and the harnessing of existing resources. An overarching approach informed by environmental, social and economic integration should be adopted to recover the built heritage and the cities that house it. Urban potential should be accurately assessed to ensure full advantage is taken of existing resources without generating false expectations and the concomitant perverse effects on the objectives of integrated urban regeneration. The development of precision tools to assess the potential for improving energy efficiency in the urban fabric is a priority. This study proposes a method for calculating energy loss across building envelopes based on the exploitation of cadastral data with open source IT tools. The output includes neighbourhood scale information on the thermal performance of building envelopes and energy dispersion relative to a city's climate based on energy loss calculations. More generally, it establishes energy efficiency of the existing urban fabric from precise energy indicators developed with pooled geometric data collected building by building from the cadastre. The method is verified by analysing the findings for a case study in an area on the outskirts of Madrid characterised by inefficient construction and listed as a deprived neighbourhood, with a population very likely to be subject to energy poverty. The methodology described can be extrapolated to other European cities with cadastres similar to Spain's and in particular to those in temperate Mediterranean climates with cold winters and warm summers. (C) 2018 Elsevier B.V. All rights reserved.