## 1 Introduction  
The construction sector stands out as a significant contributor to global energy consumption and anthropogenic carbon impacts. Efforts aimed at enhancing energy efficiency and curbing carbon emissions, formulated on both global and continental scales, can be interpreted as endeavors to mitigate the repercussions climate change could cause. Currently, the prevailing trend increasingly highlights more frequent and severe extreme events, coupled with a significant overall increase in monitored variables linked to global warming. In this context, attention in the construction sector is shifting from a narrow focus on individual buildings' energy efficiency to a broader exploration by research and policy entities at the neighborhood level, clusters of buildings, and cities [1]. Various initiatives, including the EU 100 Climate Neutral and Smart Cities program, the European Bauhaus initiative, and legislation addressing energy communities, underscore this shift toward a more comprehensive approach to decarbonizing the entire building energy infrastructure [2]. This transition aims to address the intricate aspects of building interactions, energy flexibility, grid integration, and load balancing [3]. Additionally, the urban scale facilitates a focus on critical elements such as urban planning and stakeholder involvement throughout the entire lifecycle of a neighborhood [4]. This broader perspective strives for an interdisciplinary and holistic approach to the design and management of neighborhoods and cities. Positive Energy Districts (PEDs), smart neighborhoods scaling up to smart cities and aiming towards the EU mission of Carbon neutral cities are the core tools chosen at the continental and international level to enhance the quality of life in European cities, contribute to COP climate targets, and bolster European leadership as a global model [5]. Smart cities solutions and positive energy districts will need to play a pivotal role in steering urban areas toward a low-carbon future, intending to partially cover the energy needs of nearby areas and foster the development of truly climate-neutral cities. This process involves deploying renewable energy systems within urban and regional energy frameworks, achieving high energy efficiency levels across systems and grids, implementing energy flexibility solutions, utilizing advanced materials, adopting smart energy grids, and emphasizing district-level self-consumption of renewable energy systems. Initiatives like PED JPI Urban Europe, IEA EBC Annex 83--Positive Energy Districts [6], EERA/Smart grids [7], and PED EU NET Cost Action [8] collectively strive to establish PEDs as integral components in the current building sector landscape. However, numerous challenges accompany these concepts, including the technical feasibility of achieving a positive balance in specific urban areas, the imperative for capacity-building among stakeholders, societal challenges, the enhancement of regulatory frameworks, the need for replication potential assessment, and the development of tailored business models for these specific technical solutions. According to the most widely accepted definition [9], Positive Energy Districts are defined as \"energy-efficient and energy-flexible urban areas or groups of connected buildings which produce net zero greenhouse gas emissions and actively manage an annual local or regional surplus production of renewable energy. They require integration of different systems and infrastructures and interaction between buildings, the users and the regional energy, mobility, and ICT systems, while securing the energy supply and a good life for all in line with social, economic and environmental sustainability\" [10]. The concept is thus inherently not limited to a mere mathematical balance between energy use and generation and will require deeper integration with sustainability applications as well as the social sphere [11].