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The evident need for improving the existing building stock still suffers from important barriers, such as the fragmentation of the value chain, the lack of information regarding some solutions, and the lack of confidence with respect to energy savings, which prevent unlocking investments, and the difficult communication among stakeholders. Therefore, new processes based on exploiting the potential of existing and new tools are required. In this framework, the OptEEmAL project has developed a tool that integrates stakeholders, data and tools in order to ease the process of designing energy efficient retrofitting projects at building and district scale. This tool works around an optimisation framework in order to evaluate, compare and optimise candidate retrofitting scenarios against a set of indicators showing the performance of the district. This evaluation and optimisation method is based on aggregating indicators through transforming the priorities of stakeholders into a mathematical weighting scheme, which makes it possible to provide scenarios within their expectations. Therefore, the generation of these scenarios is driven by their design parameters, being thus flexible and adapted to their needs. This paper shows the implementation of this tool and specifically 3 different prioritisation schemes, analysing how they impact into the decision making process and selection of the retrofitting strategy.Buildings account for approximately 40% of energy consumption and 36% of GHG emissions in the context of the EU [1]. When analysing the stock of existing buildings, around 30% of the building stock is more than 50 years old [2] and almost 75% is energy inefficient [3,4]. The implications of this energy inefficiency not only result in an energy and environmental cost, but also provoke other impacts, such as health problems due to the low levels of comfort within these buildings [5]. It is then imperative to focus on upgrading an ageing building stock, whose current renovation rates are low, at~1.2%. To achieve these targets, this rate should increase to 3% [6].On the other hand, the retrofitting market is quite fragmented, with multiple stakeholders with different and often conflicting interests. This is mirrored in the communication and information exchanges between them. This strong barrier is added to others, such as the lack of knowledge of some technologies among construction professionals, the varying ambition of performance requirements present within regulations, lack of awareness, and uncertainty as to the expected savings, which make

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.

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Energy geostructures (EG) are an innovative technology in the sustainable energy agenda that can be used to satisfy the heating and cooling needs of the built environment. EGs include several types of geostructures such as piles, walls, tunnels, shafts, sewers. The application of this technology to infrastructure projects is particularly interesting because of the important thermal potential offered by the large surfaces that can be thermally-activated. This study deals with thermo-active walls (Energy walls, EW), which are retaining structures used to sustain the sides of excavations. Aspects related to the hydro-thermal interactions and to the thermal design are here presented. Finally, the testing setup for the execution of a thermal response test on a recently-built EW in western Switzerland is discussed.