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The building sector is – directly or indirectly – the first pillar for application of technologies aimed at reducing energy wastes. To achieve sustainable growth goals, worldwide, the building stock needs to be re-developed from the energy viewpoint. This study focuses the attention on the building envelope, since it is the primary subsystem through which energy losses occur between inside and outside environments, by reviewing and discussing the most recent and cutting-edge researches in matter of double-skin and responsive facades for the building retrofit. Each study is investigated by characterizing the technology, the location (i.e., the climatic conditions) and season of analysis, the building intended use and the main findings. The objective is identifying potentialities and recurrent benefits related to the discussed retrofit solutions – such as reduction of energy consumption and CO2-equivalent emissions, exploitation of renewables, conceptual transformation of the building envelope – but also barriers and criticalities – such as overheating risk, lower efficiency of transparent photovoltaics compared to traditional ones, high cost of responsive elements – which have to be addressed and solved in the future. In this vein, a comprehensive snapshot of the evolution of building envelope retrofit solutions is provided with original insights into current and future trends with a view to low- (or zero-) energy buildings. Despite the critical aspects and barriers to overcome, the potential advantages make most of the addressed technologies an important tool to achieve the sustainable renovation of the existing building stock, and therefore their potentialities must be deeply investigated and understood.

This paper aims to underline the variability of constructions in Mediterranean regions, where different climates, architectural techniques and kinds of building uses determine different optimal energy refurbishments of residential buildings placed on the coastline. More in detail, by considering two different construction technologies (i.e., a lightweight house in reinforced concrete and a massive tuff-made villa), two different climates (Greek coast, climate of Athens and Italian coast, climate of Naples), two cost-optimal energy retrofits are presented. The optimized energy retrofit, performed by coupling transient energy simulations and genetic algorithm for generating improved models, have taken into account all levers of energy efficiency, and thus optimization of building envelope (thermal insulation, reflectance, windows and solar screens), active energy systems (daylight control, HVAC systems for the regulation of indoor conditions) and renewable energy sources at the building scale (namely, solar photovoltaic).

Graphical abstract, Highlights • University buildings must be safe, secure and suitable for an “in-presence” education. • Architectural and technological retrofits are necessary to face the COVID-19. • HVAC-related measures anti-contagion need studies in both time and space domains. • A numerical model of a University building, calibrated against measurements, is proposed. • The design of refurbishment is performed by coupled numerical methods, BES and CFD., The proposed investigation is aimed at providing useful suggestions and guidelines for the renovation of educational buildings, in order to do University classrooms safe and sustainable indoor places, with respect to the 2020 SARS-CoV-2 global pandemic. Classrooms and common spaces have to be thought again, for a new “in-presence” life, after the recent worldwide emergency following the spring 2020 pandemic diffusion of COVID-19. In this paper, starting from a real case study, and thus the architectural and technological refurbishment of an Italian University building (Campobasso, South Italy, cold climate), with the aims of improving the classrooms’ quality and safety, a comprehensive approach for the retrofit design is proposed. By taking into account the necessary come back to classrooms starting, hopefully, from the next months (Autumn 2020), experimental studies (monitoring and investigations of the current energy performances) are followed by the coupling of different numerical methods of investigations, and thus building performance simulations, under transient conditions of heat transfer, and computational fluid dynamics studies, to evidence criticalities and potentialities to designers involved in the re-thinking of indoor spaces hosting multiple persons, with quite high occupancy patterns. Both energy impacts, in terms of monthly and annual increase of energy demands due to higher mechanical ventilation, and indoor distribution of microclimatic parameters (i.e., temperature, airspeed, age of air) are here investigated, by proposing new scenarios and evidencing the usefulness of HVAC systems, equipment (e.g., sensible heat recovery, without flows’ contamination) and suitability of some strategies for the air distribution systems (ceiling squared and linear slot diffusers) compared to traditional ones.

The optimal control of the HVAC system in the nearly zero energy buildings (nZEBs) can be considered as a challenge. Indeed, the lack of data given by monitored data does not allow understanding what are the implications of different strategies on thermal comfort and energy consumptions. This paper determines an approach for the evaluation of the management of the heating system in an existing educational nZEB. The aim is to understand how the energy efficiency of the heating system is sensitive to controls strategies and the important role played by the control systems. The test lecture rooms on KU Leuven Ghent Technology Campus (Belgium) have been chosen as case study. A deep analysis, starting from an in-field monitoring, was carried out during the winter period of 2019, in order to assess the actual operation and the energy use of building systems under real conditions. Then, a building energy simulation (BES) model of the building and its systems was developed and calibrated against the real monitoring data. Control strategies of the heating system are simulated and compared to the current configuration. The simulation results show that strategies based on a definition of a heating curve for the boiler can reduce the comfortable time (−23%). Controlling the temperature inside the storage tank as a function of the outdoor temperature together with the control on the activation of the air handling unit result in an energy savings from 32% to 46%, with a correspondent increase of comfort time in the period from 0.6% to 3.4% compared to the baseline scenario, depending to the relationship between the external temperature and water temperature inside the water storage tank.

Buildings account for about 36% of CO2 emissions and 40% of energy consumption at EU level. Thus, a deep renovation of the building stock is fundamental to achieve the sustainability targets established worldwide. Accordingly, the study proposes an integrated approach for energy modeling and retrofit planning of districts/neighborhoods of buildings. A Geographic Information System (GIS) tool is coupled with SketchUp® to generate accurate geometrical models, while the thermophysical definition of the building envelopes is performed under DesignBuilder®. Then, EnergyPlus is used as dynamic energy simulator, while MATLAB® is the external post-processing engine. In detail, two phases are identified: 1) development of the energy model; 2) energy retrofit optimization. The approach is relevant to different scale-levels simultaneously, from a single apartment to the whole district/neighborhood as an entity. Furthemore, the use of EnergyPlus ensures high accuracy in energy predictions, while modeling the energy systems directly under MATLAB® environment strongly reduces the computational burden without affecting the results’ reliability. As a case study, part of an existing neighborhood located in Naples (Italy) and representative of the Southern Italy building stock is modeled, and its retrofit is optimized. According to the Italian laws, three retrofit levels are investigated to compare their effects on selected energy, financial and environmental indicators. Finally, two optimal solutions are selected: the “nZEB” (nearly Zero-Energy Building) and the “cost-optimal” ones. The former is the one that minimizes the neighborhood’s primary energy consumption, which passes from 116.9 kWh/m2a to 72.3 kWh/m2a, while the latter minimizes the global cost, which passes from 184.4 €/m2 to 129.6 €/m2.

Buildings account for around one third of World energy consumption and polluting emissions, thus their energy retrofit is crucial aiming at reducing the human impact on the environment. In this context, worldwide, public grant policies and stringent requirements have been adopted to promote energy efficiency in the building sector. This study proposes a comprehensive analysis to drive the energy retrofit of building neighborhoods by examining energy efficiency measures involving envelope components, heating, ventilating and air conditioning systems, photovoltaics. The effects of the creation of a local energy community that shares the photovoltaic production are taken into account too. Finally, the Italian “Superbonus 110%” public grant policy is considered, and some insights are given. More in detail, the analysis aims at minimizing at the same time the primary energy consumption and the global cost, satisfying both the public and the private stakeholders. It makes use of different software: CADMapper® and SketchUp® for modeling the geometry of the neighborhood; DesignBuilder® for realizing the first raw energy model; EnergyPlus to refine the energy model and to perform dynamic energy simulations; MATLAB® to post-process the results of the simulations. As case study, an existing neighborhood located in Naples (Italy) is investigated and three suboptimal solutions are proposed: nZEB solution, cost-optimal solution and utopia solution. Sensible reductions in energy consumption and global cost can be achieved in presence of public grants, i.e., up to 69.2 kWh/m2a and 153.6 €/m2, respectively.

The main purpose of this study is to evaluate, based on experimental data, the potential of pre-cooling the ventilation air based on ground-to-water heat exchanger, coupled with an intermediate water-to-air exchanger, during the summer period. The case study for this investigation is an existing nearly zero energy building located in Benevento, a middle-size city of South Italy with typical Mediterranean climate. Measurements of several performance parameters with four different HVAC possible configurations are shown as well as monitoring of energy uses and indoor microclimatic conditions in order to verify if comfort conditions inside the building are guaranteed together with the achievement of ‘nearly zero energy target’. Indeed, the study intends to assess the interaction between building and power grid and evaluate the temporal correspondence between building load and PV generation with hourly time step. The discussion about the hourly energy balance serves as reference to export or improve management and design strategies in regions with comparable climate conditions.

The necessity to predict building energy performance assumes a predominant role today. Present regulations in energy matter introduce pressing objectives for the energy requalification of buildings. Within spring 2020, EU Member States must adopt the European Directive 2018/844, which focuses the attention on present buildings. It establishes new obligations to retrofit the existing building stock. Solutions to improve building energy performance and to achieve economic, energy, and environmental benefits become mandatory, requiring robust and reliable procedures for energy modeling and simulation. The present study will show the importance of considering a non-standard occupant profile in energy performance simulations. The investigated edifice is a typical residential building in Naples (southern part of Italy, Mediterranean climate), built during the sixties and seventies. For the energy retrofit of the building, the most common refurbishment interventions in the Neapolitan building stock will be assessed for energy, economic and emissions savings, and thus new thermal insulation and replacement of windows. Firstly, the results will be analyzed by taking into account a standard-use profile of the occupants. Secondly, the possible wrong behaviors of users will be examined, to compare an “energy-intensive” model with the standard retrofitted model. The impact on building energy demand of the following actions will be analyzed: more energy-intensive use of the electric and lighting systems, the opening of the windows during the activation hours of the heating/cooling systems, the modification of the thermostat setpoint, the deactivation of the shading systems. The study shows a considerable increase in energy demand, following the wrong behavior of the occupants, which affects the economic convenience of the refurbishment investment. The energy retrofit is economically and energetically feasible for a standard building occupation, but sometimes wrong habits can reduce the convenience, if energy-intensive behaviors occur. This work will show that, when the numerical building model of a common building refurbishment is realized and when the cost-benefits analysis is performed, the uncertainty in occupant behavior cannot be neglected.

The green wall is an engineered technology for stormwater management and climate change mitigation at the urban level. At the building scale, these energy efficiency measures are suitable for improving indoor comfort conditions and for reducing energy needs. Several guidelines are available about vertical greening systems, but these propose design parameters and performance evaluation criteria, often incomparable. In order to facilitate the implementation of proper technical standards, this paper proposes a critical review of more recent scientific investigations. All parameters for the design optimization are discussed as well as the achievable social and private benefits by taking into consideration the type of study (numerical or experimental), the climate conditions, the analysis period, all technical requirements of the green layer as well as of the back wall. The review underlines that a multi-criteria design approach is needed for green vertical systems. Thus, the paper is concluded with a SWOT analysis, evidencing “strengths”, “weaknesses”, “opportunities” and “threats”. The analysis shows that the highlighted benefits will acquire greater relevance considering the increase in global temperatures and the growing need to redevelop densely built urban centers, while some negative aspects may be filled in the future with a deeper preparation of designers and careful choice of materials. The review paper shows, therefore, drivers and barriers occurring designing and implementing green walls.

The study provides a methodological approach for designing energy refurbishment measures of buildings, enabling to understand the uncertainty of using numerical modelling and the real impacts due of adopting some energy efficiency technologies. The case study is a University building of the centre of Italy, and the reference scenario has been supported by various in-situ surveys, investigations and evaluations of the indoor comfort. Collected data, together with a comparison with energy bills, has allowed a proper calibration of a numerical model simulated by means EnergyPlus. All this phase is described in this paper, while a second part will discuss the energy retrofit and the building energy optimization. © 2019 The Authors. Published by Elsevier Ltd.

Nowadays, the Nearly Zero Energy Buildings (NZEBs) represent the new target from 2019 onwards. The present study is focused on a single-family house (called BNZEB), placed in south Italy and specifically designed for a Mediterranean climate. The “Benevento” Nearly Zero Energy Building (that is why the name is “BNZEB”) is built with the purpose to be, at the same time, a research laboratory, suitable for testing and measuring energy demands, renewable energy conversion, indoor environmental quality and other aspects of performances in a realistic context. More in detail, firstly the BNZEB is presented and described; then, the early results of a monitoring campaign are shown with the purpose to characterise the energy performance of this building during the summer season and verify the effectiveness of chosen design solutions. For this reason, the daily energy balance is proposed with the aim to evidence the impact of solar production and electric storage on building energy consumptions. It is really important the presentation and the discussion about the monitoring results because, very often, the real performance does not coincide with the expected one and further optimizations are needed. Subsequently, a numerical model of the case study building, suitable for performing transient energy simulations, is used to compare the BNZEB building with other buildings: (a) one representative of the constructive standard established by Italian law; (b) a second one typical of the not-refurbished buildings stock of the city. The aim of this last part is to understand how much the BNZEB's energy performances are better compared to reference buildings during the summer season. Finally, the replicability of BNZEB design in Mediterranean cities, like Lisbon, Montpellier, Madrid, Seville and Athens is evaluated.

The present work concerns the energy retrofit of a public educational building at the University of Molise, located in Termoli, South Italy. The study provides a comparison of the results obtained by different dynamic simulations of passive strategies to improve thermal comfort and energy behavior of the building during the summer regime. Firstly, the building model was calibrated against historical consumption data. Then, a subsequent step involves the technical-economic analysis, by means of building performance simulations, of energy upgrading scenarios, specifically, cool roof and green roof technologies for the horizontal opaque envelope and thermal insulation, vented fa&ccedil, ade, and phase change materials&rsquo, applications for the vertical opaque envelope. Improving the indoor thermal comfort and reducing the thermal energy demand during summertime through innovative solutions will be the primary objective of the present study. The energy efficiency measures are compared from the energy, emissions, costs, and indoor comfort points of view. Phase Change Materials applied to the inner side of the external walls are analyzed in depth and, by varying their melting temperature, optimization of design is performed too. This innovative material, with a melting temperature of 23 &deg, C and a freezing temperature of 21 &deg, C, determines the reduction of summer energy consumption of 11.7% and the increase of summer indoor comfort of 215 h. Even if consolidated, other solutions, like the cool roof, green roof, thermal insulation, and vented fa&ccedil, ade induce improvements in terms of summer energy saving, and the percentage difference compared to the basic building is less than 2%. For this case study, a Mediterranean building, with construction characteristics typical of the 1990s, traditional passive technologies are not very efficient in improving the energy performance, so the investigation focused on the adoption of innovative solutions such as PCMs, for reducing summer energy demand and improving indoor thermal comfort.

The first part of this study provided a discussion about the methodological approach for designing energy refurbishment measures of buildings. The case study is a building owned by University of Molise, in Campobasso, a cold Italian city. The reference scenario is a numerical model built after deep investigations, and thus surveys, questionnaires, documents and experimental measurements on the real building. Then, a calibrated energy model was presented. In this second part, starting from the calibrated model, some energy retrofit measures have been implemented. The obtained results allow to discuss two key points for researches in matter of energy refurbishment of buildings: a) the importance of using validated models to simulate the present performance; b) the environmental benefits and the economic implications of a deep energy refurbishment. © 2019 The Authors. Published by Elsevier Ltd.

Many strategies are under investigation to reduce the environmental impact of the building stock. Among them, the implementation of optimal operation strategies of the HVAC (heating, ventilating and air conditioning) systems plays a fundamental role because it can produce substantial energy-economic savings and increment of thermal comfort. In this vein, a weather-data-based control framework is here proposed to provide optimal heating operation strategies easily applicable to a huge number of buildings. It works by coupling EnergyPlus and MATLAB® to run a multi-objective genetic algorithm and proposes a novel approach for multi-criteria decision-making. This latter addresses characteristic days (i.e., average cold days, average days and average hot days) of weather data files with the aim to provide monthly heating strategies that ensure the best compromise between running cost and thermal discomfort. As case studies, the proposed framework is applied to a residential building, representative of the Italian building stock from 1961 to 1975. In order to cover most of the Italian territory, four different cities are considered: Palermo (climatic zone B), Naples (C), Florence (D) and Milan (E). The achieved cost reduction is included between 6% (Milan) and 34% (Palermo), while the thermal comfort is not penalized. Finally, the framework provides practical indications ready to be easily applied to the Italian residential stock to achieve a significant and widespread improvement of energy performance. © 2019 Elsevier Ltd

This study offers deep insights into the link between climatic stress and building heating performance. Two representative Italian residential buildings – existing and newly-built, respectively – are investigated by predicting heating demand for 63 locations, covering all typical national climates. Two simulation software are used – i.e., TERMUS® and EnergyPlus –, to compare a standard semi steady-state approach with a more accurate dynamic one. The comparison enables to understand the influence of the climatic stress on different levels of building modeling/simulation. Notably, the semi steady approach can provide reliable outcomes (close to the dynamic one) for existing buildings in cold climates. Then, a sensitivity analysis is conducted to investigate the correlation between climatic parameters and yearly heating demand, showing that the heating degree day index does not provide a complete explanation of such demand. Indeed, it does not take into account latitude and/or solar radiation, whose influence is not negligible. Therefore, a novel heating stress index is proposed, including normalized heating degree day and latitude. Its expression is optimized through a Pareto approach to ensure the best fitting/regression of yearly heating demand for both building typologies. The achieved determination coefficient (R2) is 0.990 for the existing building, 0.995 for the newly-built one. Finally, climatic stress curves are achieved to predict heating demand and related running cost as a function of the proposed index, providing a user-friendly but reliable tool to forecast building heating needs.