Nowadays, urbanists are facing increasing demands regarding the performance of urban development projects in terms of environment, quality of life and socio‐economic issues. In order to address these increasing demands, actors involved in urban development projects need tools capable of assessing their impacts. These tools should also enable the comparison of all potential scenarios. Taking into account these needs, Nobatek and Tecnalia have developed NEST (Neighbourhood Evaluation for Sustainable Territories), which is one of the first tools that allows for a simultaneous environmental, economic and social analysis at the district scale, with a life‐cycle perspective. Using NEST, the authors of this work carried out an environmental and social evaluation of three districts in the city of Donostia, in the framework of the Essai Urbain research project. The evaluation first consisted of analysing baseline environmental impacts of the three districts. Then, with the objective of reducing environmental impacts and increasing social well‐being, the authors proposed several refurbishment scenarios for the studied districts, focusing on energy issues. The study was performed in close collaboration with the city of Donostia, which enabled the identification and selection of the most relevant scenarios from an environmental standpoint. Moreover, the NEST software has caught the attention of the project's stakeholders regarding environmental issues. Finally, NEST seems to be an interesting alternative in accounting for sustainable development issues from the early stages of urban development projects.