The increased effects of climate change in the built environment require a rapid and effective response to adapt urban settlements to the main impacts related to heatwave, extreme precipitation, sea-level rise, and so on. At the same time, there is not much time to reduce Greenhouse Gas (GHG) emissions that contribute to climate change and limit the mean temperature of the planet within the 1.5 °C imposed by the Paris Agreement. In this perspective, cities around the world have a key role toward carbon neutral and resilient targets. In parallel in the last years, we are witnessing the impacts of a big amount of data and information available at the city scale. There are many data coming from different databases that can be processed and managed to support the urban climate action planned and designed by decision-makers and urban practitioners, for example, to assess the carbon emission of the building sector or to simulate the effects of extreme precipitation or urban heat island and consequence behavior of the built environment. In this scenario, in the last years, among many different digital enable technologies available in the Industry 4.0 ambit, it has gained more attention in the field of urban planning and urban design the digital twin concept that could synthesize in a digital representation of the real-world data and information flow that could exchange from the physical side to digital representation and vice versa. The aim of the paper is to analyze the urban digital twin developed in last years in Europe to evaluate if and how they consider the climate change issue, in order to understand the state of the art, the applications developed for climate change and which is the level of experimentation in order to study and develop guidelines to build urban digital twin as a support tool for a climate-neutral and resilient city.

Cities worldwide have established plans and policies to achieve climate-neutral and climate-resilient objectives in recent decades. Researches have demonstrated that Climate Change Action Plans generally fail to include mitigation and adaptation approaches in their planning processes, despite their importance. A proposed multilevel assessment of Climate Change Action Plans, urban regeneration, and building projects was used to analyze the ten cities most sustainable in terms of developing environmental strategies, including local climate action to determine the degree of adaptation and mitigation integration in cutting-edge contexts and to identify measures that show synergies and co-benefits for urban design practices. Climate Change Action Plans, urban regeneration and building projects have been evaluated through scoring methods to determine firstly the level of integration among adaptation and mitigation and secondly the most used urban design solutions that addresses both approaches. Almost all of Climate Change Action Plans have "moderate" and "early" integration, with the most advanced in North American cities including Toronto, Montreal, New York, and San Francisco. Climate Change Action Plans partly influence urban regeneration projects. Among the cities studied, Royal Seaport and Hammarby Sjöstad in Stockholm stand out as the most advanced in terms of including measures for both mitigating and adapting to climate change, as well as the extent of activities carried out. North American building projects have the highest adaptation and mitigation strategies. Climate Change Action Plans, urban regeneration initiatives, and building projects analyzed have displayed measures to include both climate change mitigation and climate change adaptation benefits into urban design.

In the new context of the trialling and the development of the materials, buildings systems and innovative processes required to meet new challenges posed by environmental transition in Europe and across the globe, the construction sector urgently needs to define more sustainable development models to achieve decarbonisation, as is the case in other sectors. In this context, recent experiences of incorporating photovoltaics into architecture are a clear sign of a change in focus on how systems are integrated into architectural design: a new way of viewing the technological innovation of PV modules which is ever more closely linked to the architectural design right from the initial concept stages. The study we present is based on a critical analysis of the current international state of the art of architectural design incorporating photovoltaics, selecting case studies which illustrate best practice for technological innovation to demonstrate possible scenarios for future developments. Therefore, all the principle approaches identified by the international research will be described as well as the impact that these technological developments are having on architectural style and quality of life in cities. With regard to the aesthetic and formal properties that are the dominant feature of recent practice for the integration of photovoltaics, the study will highlight further areas of research with a view to defining a component of the building shell in which the generation of energy from renewable sources represents just one of the potential components of a system integrated into the architectural style. In addition, the intention is to demonstrate that the architectural designs analysed can be considered to be the result of a close relationship between designers, applied research and the industrial sector; therefore, technological innovation of photovoltaic products will inevitably be linked to a deeper and fundamental innovation of processes leading to these results.

The transition towards circular practices in the construction sector requires integrated approaches addressing both material resource procurement and the fragmentation of local stakeholder networks. This study presents the ACT-FLOW Framework, a multi-level approach enabling territorial circular processes by integrating actor networks and material flows. The framework comprises three interconnected levels (strategies, processes, and indicators) supporting the definition, implementation, and evaluation of circular practices across building and territorial scales with an iterative refinement phase. Methodologically, it was developed through a Design Science Research approach (DSR) articulated into four steps: (1) define the scope and boundaries; (2) develop a knowledge base; (3) structure the framework and its components; and (4) validate and apply it to a real case, the Circular Design Polito Lab, a research infrastructure currently under development by the Politecnico di Torino (Italy). The results demonstrate how the framework supports stakeholder coordination, structures circular workflows, and enhances circular performance monitoring. The primary limitation is that the case study has not yet been realized; consequently, it is not feasible to conduct an ex post but only an ex ante evaluation of the results. Future research will assess the framework’s capacity to foster ecosystemic conditions for circular construction practices through its longitudinal application across project phases.

The construction sector generates over one-third of all waste in Europe, yet the reuse of building components remains marginal compared to recycling, and circular strategies are rarely aligned on the territorial scale at which materials, stakeholders and infrastructure operate. This paper investigates the regulatory, institutional, infrastructural and operational conditions under which reuse to become a systemic practice. A desk-based comparative analysis of six European contexts (Belgium, the Netherlands, Switzerland, Germany, France, Denmark) was conducted on 282 documents, using a framework of seven dimensions grouped into three macro-families drawn from the literature on territorial circular ecosystems. The findings show that these conditions form a dependency chain of five ordered links: legal recognition of the non-waste status; a standardized pre-demolition audit; preparation and storage physical hubs, in parallel with research infrastructures, absorbing technical uncertainty; a guarantee system covering performance, liability and insurability; and a demand-side activation. The guarantee link is a constraint and a key element in demand activation. Regulation is necessary but not sufficient, since binding instruments target recycling or auditing while reuse remains voluntary in all six contexts. The chain yields a typology of ecosystem configurations and a replicable diagnostic instrument, whose transferability is assessed on the Italian case.

Urban areas face increasing challenges from climate change and require comprehensive approaches to address both mitigation and adaptation. The complexity of this integrated approach can be tackled through the adoption of digital enabling technologies in the realm of smart cities. In recent years, numerous Urban Digital Twins have been developed by cities worldwide to better support planners and designers with data, simulations, and visualizations.This study explores the integration of climate change mitigation and adaptation within Urban Digital Twins. The research identifies factors that are often overlooked in current implementations and provides guidelines for structuring Urban Digital Twin modules. By analyzing key functionalities and requirements, as well as insights from stakeholder interviews, this work highlights the potential of Urban Digital Twins in fostering holistically climate-proof urban development.Key findings emphasize the importance of incorporating climate-related variables across Urban Digital Twin functions to support decision-making in urban regeneration and new urban development projects. Despite challenges such as data integration, the proposed guidelines aim to inform future Urban Digital Twin development efforts, enhancing their role in planning and designing more resilient urban areas. The paper presents a case study on the Urban Digital Twin of Helsinki, outlining essential factors and their implications for urban climate-proof decision-making.