We studied the structure of the 15-minute city by measuring the distances from the services on spatial graphs. While the concept of the 15-minute city is rapidly spreading, its operative definition can be of help for planning and understanding the possibilities of the general idea. For three European cities (Rome, Paris, and London), we developed a method to calculate pedestrian travel time to reach services for all the possible paths on urban graphs, finding that the 15-minute city generally has multiple connected components and that the services have not necessarily been part of it. This algorithm was used to to make a quantitative comparison between the cities, showing that Paris and London have a stronger 15-minute characterization than Rome. By generalizing the method, it was possible to define a 15-minute urban index, which quantitatively characterizes this city feature. The results seem to be promising because, at the cost of the massive use of computational time, a digital model for the city can be generated: a planning tool to simulate urban solutions and a rigorous criterion for evaluating how much a city can be considered a 15-minute city.

Cities need to make themselves energy self-sufficient by exploiting renewable sources and, above all, to evaluate the potential and constraints that each city can express by virtue of its own characteristics. This study focused on how the realisation of a renewable energy community could be approached in urbanised contexts. The methodology involved the selection of three case studies in Rome analysing the feasibility, programming and design scale, and the implications of planning RECs. Through simulation at three levels of detail, this study identifies elements to assess the feasibility of RECs and to elaborate scenarios to support their planning and dimensioning. The practical importance is to identify a possible methodological path and relevant factors which public or private stakeholders can consider at different levels in setting up RECs in an urban context. The research conclusions of these simulations point out that the specificities of a context affect many factors, among which an important role is played by the facilities and spaces for public use, as they are synergetic to a shared use of energy between residential and non-residential functions, but above all, because they are also available to accommodate services for the energy community.

Cities are the main field of application of technological innovations for ecological transition and decarbonisation. With reference to its proximity spaces, the research proposes a multidisciplinary and transcalar vision in which analytical and quantitative methods of urban design are combined with qualitative assessment methods of technological design to simulate and measure the impacts of interventions in terms of mitigation and adaptation to the effects of climate change. A planning support tool, based on game theory, guides the choice between effective and interdependent solutions for decarbonisation through renewable energy production, ecosystem services and accessibility to essential services.

The history of lightness might not only recount aeroplanes and low-density materials, it might also speak of a need for dematerialisation consistent with the control of resource consumption and greenhouse gas (GHG) emissions. Following the Paris Agreement, carbon neutrality policies had initially focused on mitigation actions for energy efficiency and low-carbon sources. Although crucial for the materials industry, other strategies, especially on the demand side, are possible to reduce their production. In the context of the circular economy applied to the built environment, Material Efficiency (ME) constitutes a set of actions for circular design for which functions, configurations and construction processes need to be reinvented.

This study investigates the application of the Positive Energy District paradigm to two existing and morphologically diverse urban districts in Rome: Testaccio and Valco San Paolo. The research aims to evaluate the feasibility and effectiveness of district-scale energy retrofitting strategies, integrating dynamic simulation tools to model current energy behavior and assess future scenarios. The methodology combines a range of interventions including envelope insulation, high-performance glazing, HVAC system upgrades, efficient lighting solutions, and large-scale photovoltaic deployment. Additionally, the study explores the potential benefits of energy storage systems, with particular focus on the optimal sizing of lithium-ion battery solutions to enhance local self-consumption and reduce grid dependency. Key performance indicators are used to analyze the alignment between renewable energy generation and district demand, as well as the interaction with the electrical grid. By calibrating simulation models with real thermophysical and consumption data, the research ensures methodological robustness and enables the replicability of the proposed approach in other urban contexts. The study offers a comprehensive framework for planners and policymakers seeking to support the decarbonization and resilience of urban districts through the implementation of PEDs. Future developments will focus on optimizing storage management, assessing the environmental impact of battery life cycles, and integrating PEDs within broader urban energy ecosystems.