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In response to the pressing need to increase energy efficiency in buildings, new regulations are continually being introduced to enforce higher standards. The recent recast of the Energy Performance of Buildings Directive (EPBD IV) emphasizes the establishment of national performance standards, which will supposedly be based on the national Energy Performance Certificate (EPC). However, energy certifications across several European countries rely on a quasi-steady state approach, which fails to accurately represent real-performance conditions due to inherent limitations. This is more evident in buildings located in warm climates, where actual energy demands far exceed those predicted by energy certifications. To address these discrepancies, a shift towards dynamic performance assessment methods is pivotal. This research compares the heating and cooling energy demand of an office building using two approaches: the quasi-steady state, prescribed by the Italian standard, and the dynamic state. After calibrating the dynamic model, it was employed to perform a simulation incorporating more detailed user profiles and boundary conditions than those used in the quasi-steady state method. This approach allows the preservation of both reasonable accuracy and practical applicability. Finally, a sensitivity analysis of influential parameters seeks to elucidate the main causes of divergence between simulated and measured performance and to identify opportunities for improving EPC. The simulation outcomes indicate that, while the stationary model yields heating energy demand relatively aligned with the measured data, it shows substantial discrepancies (about 50%) in the cooling predictions. Moreover, the findings reinforce the inadequacy of the simpler approach and advocate for the integration of dynamic state simulation in energy performance assessment, aligning with the objectives of the recent EPBD.

The European Union’s LEVEL(S) framework establishes a standardized methodology for evaluating and documenting the sustainability of buildings across Europe, aiming to enhance the sustainability, competitiveness, and resilience of the EU’s built environment. This study investigates the theoretical foundations and practical applications of the LEVEL(S) framework in advancing sustainable building practices. The research begins with a systematic identification of gaps in existing sustainability indicators, such as the absence of specific metrics and undefined thresholds, identified in the author’s previous work. To address these gaps, the study introduces new thresholds informed by an extensive review of the relevant literature and performance data. Additionally, the research synthesized a comprehensive Table by analyzing EU user manuals, the related academic literature, and various Green Building Rating Systems (GBRSs), thereby facilitating the extraction of pertinent standards and regulations. Collectively, these findings provide valuable resources for policymakers and stakeholders, ensuring that the recommendations are closely aligned with the LEVEL(S) framework and can be effectively applied to real-world building projects throughout Europe.

Over the past few years, the Covid-19 pandemic has triggered an economic crisis, impacting various sectors including building construction. Within this sector, the residential section represents one of the main causes of energy consumption and pollutant emissions. To address this challenge the European Union has devised a strategic plan aimed at promoting energy efficiency and environmental sustainability, with a special focus on revitalizing the building sector. Within this strategic framework, the tax incentive Superbonus 110% introduced in 2020 has emerged as a pivotal program, incentivizing specific energy efficiency measures for existing buildings in alignment with the EU Directives. In this regard, this study aims to analyse the retrofit intervention of two existing residential buildings subsidized through the Superbonus 110% mechanism. A critical analysis of several passive and active energy efficiency measures is performed considering energy, environmental and economic indicators, employing a dynamic simulation approach. This work demonstrates how the proposed Italian funding program can enhance the diffusion of energy efficiency interventions. However, thanks to the analysis of real case studies, the criticalities and implications that such a mechanism has brought to the construction sector were highlighted, in the perspective of future incentives.

Among renewable energy generation technologies, photovoltaics has a pivotal role in reaching the EU’s decarbonization goals. In particular, building-integrated photovoltaic (BIPV) systems are attracting increasing interest since they are a fundamental element that allows buildings to abate their CO2 emissions while also performing functions typical of traditional building components, such as sealing against water. In such a context, since one of the main challenges to decarbonizing the building sector lies in the retrofitting of existing buildings, the current paper is focused on the design, development, and testing of a novel roofing BIPV system. The entire research was carried out as part of the Horizon 2020 HEART project. In more detail, the research analyzed the requirements of typical pitched tile roofs, which are currently the most common type in Europe, and developed a universal photovoltaic tile that can be easily and quickly integrated into such a type of roof. The research was also aimed at minimizing the embodied energy of the component and promoting disassembly and recycling at the end of life, fully in line with a circular economy perspective. The adopted design and development processes are described in detail in the present paper, along with the results of several tests performed in the field. In addition, further development prospects of the component, aimed at meeting the integration requirements in historic buildings, are finally presented.

In Europe, the recent application of regulations oriented to zero-energy buildings and climate neutrality in 2050 has led to a reduction in energy consumption for heating and cooling in the construction sector. The thermal insulation of the building envelope plays a key role in this process and the requirements about the maximum allowable thermal transmittance are defined by country-specific guidelines. Typically, high insulation values provide low energy consumption for heating; however, they may also entail a risk of overheating in summer period and thus negatively affect the overall performance of the building. In addition, the embodied energy and related emissions caused by the manufacturing and transportation processes of thermal insulation cannot be further neglected in the evaluation of the best optimal solution. Therefore, this paper aims to evaluate the influence in terms of embodied and operational energy of various walls’ thermal insulation thicknesses on residential buildings in Europe. To this end, the EnergyPlus engine was used for the energy simulation within the Ladybug and Honeybee tools, by parametrically conducting multiple iterations; 53 variations of external wall U-value, considering high- and low-thermal-mass scenarios, were simulated for 100 representative cities of the European context, using a typical multifamily building as a reference. The results demonstrate that massive walls generally perform better than lightweight structures and the best solution in terms of energy varies according to each climate. Accordingly, the wall’s thermal transmittance for the samples of Oslo, Bordeaux, Rome and Almeria representative of the Continental, oceanic temperate, Mediterranean, and hot, semi-arid climates were, respectively: 0.12, 0.26, 0.42, and 0.64 W/m2K. The optimal solutions are graphically reported on the map of Europe according to specific climatic features, providing a guidance for new constructions and building retrofit.

This article presents the use of phase-change material (PCM) thermal storage within the Horizon 2020 HEART project (Holistic Energy and Architectural Retrofit Toolkit), aimed at decarbonising the European building sector through the retrofitting of existing structures into energy-efficient smart buildings. These buildings not only reduce energy consumption, but also incorporate advanced technologies for harnessing green energy, thereby promoting environmental sustainability. The HEART project employs state-of-the-art technologies for electricity production/dispatching and heat generation/storage, managed by a cloud-based platform for the real-time monitoring of parameters and optimising energy utilisation, enabling users to control their environmental comfort. The article provides a detailed examination of one of the project’s demonstration sites in Italy, focusing on various components such as heat pumps, photovoltaic systems (PV), controllers, and particularly emphasising the significance of storage tanks. The study involved the measurement and analysis of three heat storage tanks, each with a total volume of 3000 L. These tanks utilised PCM modules for latent heat storage, significantly enhancing overall heat accumulation. Water served as the heat transfer fluid within the tanks. Through meticulous calculations, the article quantifies the accumulated heat and presents a comparative evaluation between PCM-based storage tanks and conventional water tanks, showcasing the advantages of PCM technology in terms of increased heat retention and efficiency.

The current energy-environmental emergency requires urgent actions, especially for retrofit existing buildings in line with EU Renovation Wave targets and decarbonization strategies. The paper presents the optimization process of a dry envelope system based on sandwich panels, developed and engineered within “RE-SKIN” Horizon project. Rather than introducing new materials, the approach upgrades state-of-the-art technologies to enhance performance while minimizing environmental impacts. Through close collaboration with consortium partners, the design evolves from conventional to low-impact materials, integrating low-impact coat steel layers and bio-based PUR foam insulation. A comprehensive Life Cycle Assessment (LCA) identifies environmental hotspots, guiding impact reductions between the initial and optimized design solution. The suggested sandwich panels enhance energy efficiency while enabling smart building integration for real-time monitoring, all while supporting circular resource use as a sustainable alternative to standard insulation coatings.

The application of sustainability assessment in a decision context is associated with various challenges that explain why the transition to action-oriented knowledge still needs to be fulfilled. Therefore, this paper aims to explore the associated challenges in sustainability assessment in the decision context of the built environment. Several publications are reviewed to provide a systemic understanding of the associated complexities. The challenges in sustainability assessment in the built environment are categorized at different levels, from understanding to measurement and implementation. The challenges are further categorized into definition, context, interpretation, data, measurement methods, uncertainties, indicators and indices, results, coordination, conflicts, and action-oriented knowledge. Moreover, according to the nature of each challenge, they are classified into epistemological, methodological, and procedural challenges. The novelty of this review is that it reviews and reports almost all fragmentedly reported challenges in sustainability assessment of the built environment in the literature within a holistic framework that provides a clear understanding of the state of the art and second discusses them within an integrated framework (the Sustainability Assessment Network) including the position of active-role players to resolve them, including strategists, scientist, and stakeholders.

The indoor climate of non-climatized churches is usually subject to cyclical fluctuations of temperature and relative humidity induced by external climate conditions which might be dampened by the high thermal capacity of their envelope. However, several phenomena affect their indoor climate (e.g., internal gains due to people and artificial lighting, air infiltration, etc.), which lead to environmental variations that might jeopardize the artworks contained within. In particular, one of the most influential parameters that may affect non-climatized churches is the massive and intermittent presence of people who constantly visit their spaces. In such regard, long-term monitoring allows the collection of environmental data with different building operation conditions and visitor fluxes. This paper analyses the indoor climate of the Milan Cathedral (Duomo di Milano) in Italy for three continuous years (including the lockdown period that occurred in 2020 caused by the COVID-19 pandemic), with a focus on visitors’ effects on the indoor environment and the conservation of the main artworks contained within. The results of the analysis have shown that spaces with huge volume are most influenced by the opening of the doors rather than the hygrothermal contribution of the intermittent presence of massive crowds. Moreover, the absence of visitors for a prolonged period correlates with an improvement in the indoor conservation conditions for artworks, especially those made of hygroscopic materials, due to the reduction in short, rapid climate fluctuations.

When considering the deployment of renewable energy sources in systems, the challenge of their utilization comes from their time instability when a mismatch between production and demand occurs. With the integration of thermal storages into systems that utilize renewable energy sources, such mismatch can be evened out. The use of phase-change materials (PCMs) as thermal storage has a theoretical advantage over the sensible one because of their high latent heat that is released or accumulated during the phase-change process. Therefore, the present paper is a review of latent thermal storages in hydronic systems for heating, cooling and domestic hot water in buildings. The work aims to offer an overview on applications of latent thermal storages coupled with heat pumps and solar collectors. The review shows that phase-change materials improve the release of heat from thermal storage and can supply heat or cold at a desired temperature level for longer time periods. The PCM review ends with the results from one of the Horizon2020 research projects, where indirect electrical storage in the form of thermal storage is considered. The review is a technological outline of the current state-of-the-art technology that could serve as a knowledge base for the practical implementation of latent thermal storages. The paper ends with an overview of energy storage maturity and the objectives from different roadmaps of European bodies.