The building sector has a central role in achieving the European goals of a zero-emission and fully decarbonized stock by 2050. Among the provisions of the Energy Performance of Buildings Directive (EPBD) recast, the implementation of the cost-optimal methodology marked a novel approach in the establishment of minimum energy performance requirements for new and existing buildings. Member States must develop cost-optimal calculations every 5 years to verify and accordingly update the national requirements in force. This paper analyses the latest national cost-optimal reports, providing an updated assessment of the implementation of the cost-optimal methodology throughout Europe. It quantifies the progress in reaching cost-optimal levels in comparison with the previous assessment. It focuses on the conformity and plausibility of calculations in compliance with the policy framework. Furthermore, it evaluates the gap with national requirements, showing that the gap is higher than 15% only in a few Member States. The results provide a comprehensive review of the European progress towards cost-optimality in both the residential sector (average cost-optimal level 80 kWh/m²y for new, 130 kWh/m²y for existing buildings) and the non-residential sector (140 kWh/m²y for new, 180 kWh/m²y for existing buildings). An overall positive development can be inferred from the analysis of the Member States’ progress in the methodology’s implementation. The review also gives inputs for the cost-optimal methodology update foreseen for 2026 (e.g., cost-optimality for districts and historical buildings). The outcomes assume a crucial relevance for the ambitious energy efficiency targets established by Europe.

The building sector is crucial in all of the possible net zero scenarios suggested for the European Union. In this area, the Italian situation is exemplary. Italy suffers from an aging and low-performance building stock and needs to increase its annual rate of energy retrofits in order to achieve its 2030 and 2050 targets. Even though since at least 2007, several different incentives schemes intended to stimulate energy-efficiency interventions have been in place, Italy has not been sufficiently able to promote deep retrofits. In 2020, in order to help the economy recover after the lockdowns that were introduced to face the first phase of the COVID-19 pandemic, the existing incentives were increased to up to 110% of investments for interventions that improved the energy class by at least two grades. This so-called “Superbonus” was also extended to the public social housing sector thanks to a credit assignment scheme. Given the results of this provisional phase, a possible policy roadmap for the energy renovation of the residential and educational building stock in Italy is presented in this paper through an analysis of data related to the implementation of current instruments in terms of number of interventions, investment needed, energy savings and evaluation of potential benefits and costs that can derive from an increase in the current deep-renovation rate. Through definition of a long-term renovation strategy, this paper illustrates how market barriers and other issues in instrument design can be tackled and how policymakers can help to develop a sustainable long-term roadmap for energy-efficient buildings. Beyond the residential sector, public buildings, particularly educational buildings, are taken into consideration as well, as they are places of collective use that represent the social values of fairness and sustainability and can therefore have an exemplary role for private initiatives.

Community energy is a buzzword that has historically included various type of experiences. In 2018, the Renewable Energy Directive (RED II) legally defined renewable energy communities (RECs). Based on the first pilot projects and on the Italian legal framework, a possible REC configuration of municipal initiative with a high replicability potential is one in which a photovoltaic system is installed in educational buildings and shares energy with neighbouring residential consumers. This analysis presents an economical evaluation of different possible scenarios depending on variables such as solar radiation, system capacity, fraction of self-consumption within the REC, installation costs and energy prices. All the scenarios identified and analysed show positive economic indexes, although the energy and economic results may significantly vary depending on the variables studied. In the analysed case studies, the Net Present Value (after 20 years) is between kEUR 51 and kEUR 478; the internal rate of return is between 9.5% and 88%; the payback time is between 13.6 years and 1.1 years. The results of this analysis are relevant as they allow us to better understand the critical factors that can enable REC in providing local economic and social benefits to have a real impact on energy poverty or on the provision of local social services.

This data article relates to the paper “Review of the cost-optimal methodology implementation in Member States in compliance with the Energy Performance of Buildings Directive”. Datasets linked with this article refer to the analysis of the latest national cost-optimal reports, providing an assessment of the implementation of the cost-optimal methodology, as established by the Energy Performance of Building Directive (EPBD). Based on latest national reports, the data provided a comprehensive update to the cost-optimal methodology implementation throughout Europe, which is currently lacking harmonization. Datasets allow an overall overview of the status of the cost-optimal methodology implementation in Europe with details on the calculations carried out (e.g., multi-stage, dynamic, macroeconomic, and financial perspectives, included energy uses, and full-cost approach). Data relate to the implemented methodology, reference buildings, assessed cost-optimal levels, energy performance, costs, and sensitivity analysis. Data also provide insight into energy consumption, efficiency measures for residential and non-residential buildings, nearly zero energy buildings (NZEBs) levels, and global costs. The reported data can be useful to quantify the cost-optimal levels for different building types, both residential (average cost-optimal level 80 kWh/m²y for new, 130 kWh/m²y for existing buildings) and non-residential buildings (140 kWh/m²y for new, 180 kWh/m²y for existing buildings). Data outline weak and strong points of the methodology, as well as future developments in the light of the methodology revision foreseen in 2026. The data support energy efficiency and energy policies related to buildings toward the EU building stock decarbonization goal within 2050.

This paper presents an overall concept developed by ENEA (the Italian National Agency for New Technologies, Energy and Sustainable Economic Development) in the Italian framework of renewable energy communities (RECs). The proposed work is driven by the idea that RECs are part of a long-term vision aimed at achieving the broader concept of smart communities (SCs) through smart energy communities (SECs). SECs are, therefore, the evolution of RECs toward SCs, where ICT (information and communications technology) and digitalization play a pivotal role in fostering and boosting the energy transition and addressing societal challenge goals by 2050. In this scenario, the proposed approach is based on three dimensions, as follows: digital tools, use cases, and the observatory. Digital tools can be utilized at different stages of the creation of RECs, ranging from the design and engagement phase to evaluation, analysis, and the token economy. The second dimension refers to some selected different business cases that are used to test and demonstrate the proposed tools and provide support to specific RECs in the different phases of their creation. Lastly, the EC observatory was created by ENEA to provide necessary support to the market and stakeholders on different aspects, such as data management, economics, legal issues, communication, and regional governance.