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A significant part of the housing stock in southern Europe is obsolete and in need of extensive retrofitting to improve its energy performance and thermal comfort. However, before adequate retrofit measures can be proposed for this housing stock, the characterization of current building performance is fundamental. Although the simulation tools frequently used and widely accepted by the scientific community ensure accurate results, these require high computational times. The main aim of this paper is the development of a surrogate model to speed up the thermal comfort prediction for any member of a building category, ensuring high reliability by testing the entire simulation process with real data measured in-situ. To this end, an artificial neural network (ANN) is generated under MATLAB® environment using the data obtained from EnergyPlus simulations for linear-type social housing multi-family buildings in southern Spain, which were constructed in the post-war period. The developed ANN provides a regression coefficient between simulation targets and ANN outputs of 0.96, with a relative error between monitored and simulated data below 9%. A further result is that the building category characterization shows a general lack of suitable indoor thermal comfort conditions, thereby showing the great need for effective retrofit strategies.

Facing the climate change is a common priority, due to ethical issues related to general concept of sustainability and livable future for the next generations. Moreover, ethical aims for contrasting energy poverty, heat-related diseases and deaths, availability of food and water, infections and viral-bacteriological risks, meteorological extreme phenomena, such as floods and intense and destructive precipitations, are stringent and pressing targets. All serious and independent investigations reveal future scenarios of an overall global warming that surely make worrying the evolution of quality of life on this earth. Each one has to do his part. In this study, the research is focused on renewable technologies for the passive cooling of buildings. Indeed, the space cooling is a strongly increasing use of energy and induces a vicious circle, being, at the same time, a cause and an effect of the anthropogenic overheating of the planet. The paper mainly reviews techniques for suitably governing the energy interaction between buildings and surrounding environment. The energy efficiency concerns the building envelope design, the use of efficient HVAC systems, adoption of renewable energy on-site. On the other hand, every energy conversion process determines waste heat, so that also a ‘free of operational cost’ solar cooling system however causes dissipation of heat into the ambient. Finally, renewables cannot be the unique solutions for supplying the energy required for the building use. Conversely, strategies for reducing the building cooling are needed, and these are reviewed in this study. In thermodynamics terms, the building is seen as part of the system and not the mere control volume. Greenery of facades and roofs, phase change materials, nocturnal convective cooling, evaporative and ground cooling, solar systems such as chimneys for improving the building ventilation are here discussed, as well as emerging technologies such as breathing walls and dynamic insulation. The reviewed studies, selected on the basis of more recent progresses concerning the investigated technologies, revealed potentialities but also criticalities in the design.

Building activity is the sector that affects for the most part the anthropogenic climate change. Indeed, even if differences can be found among countries, according to the level of development and climates, buildings require about 30–40% of the overall energy demand, with similar share concerning the greenhouse emissions. According to the more recent EU Directives in matter of energy efficiency in energy use, a great attention has to be paid to energy refurbishments of existing buildings. Indeed, the turnover rate of the EU building stock is generally low in fully-developed countries, so that the energy retrofits are also more important compared to new nearly zero-energy buildings. The proposed investigation concerns the demonstrative role of the public hand, whose necessity is underlined by the EU Directives 2010/31/EU and 2012/27/EU, through a multi-step and multi-objective optimization of an educational building of an Italian University. All preliminary investigations aimed at a reliable modelling, the iterative method that combines genetic algorithms and transient energy simulations tailored on calibrated numerical models make the investigation complete and repeatable. All levers of energy efficiency have been pressed, and thus the refurbishment of building envelope, HVAC systems, integration of energy supply by renewables. The multi objective optimisation concerns costs, incentives, indoor comfort, energy demands for heating and cooling and a novel approach is proposed for choosing the best configuration of retrofit. It is resulted that the most profitable energy efficiency measures involve the modernization of energy systems, even if also the retrofit of the building envelope can be profitable under favourable financial conditions. The cost-effective refurbishment reduces the primary energy demand up to a value of 12 kWh/m2a, so that the building can be surely considered as nZEB.

A new comprehensive approach is proposed to support cost-optimal design of building envelope’s thermal characteristics and HVAC (heating, ventilating and air-conditioning) systems in presence of a simulation-based model predictive control (MPC) for heating and cooling operations. The cost-optimal solution is identified through a main mono-objective genetic algorithm (GA) that minimizes global costs for space conditioning. The explored solutions represent building thermal designs integrated with the MPC of HVAC systems. For defining the MPC strategies, the main GA launches two secondary bi-objective GAs that optimize heating and cooling operations, respectively. These secondary GAs perform Pareto optimizations by minimizing operating costs and thermal discomfort. They provide the optimal hourly set point temperatures for heating and cooling operations, with a day-ahead planning horizon, by considering the forecasts of weather conditions and building use. The optimal control strategies are found based on requirements of users, who set a minimum comfort level to be fulfilled. The GAs are implemented by coupling MATLAB ® with EnergyPlus. The methodology is applied to a new multi-zone residential building in Naples (Southern Italy). It yields primary energy savings around 35.4 kW h/m 2 a and global cost savings around 7000 €, ensuring the same satisfying comfort level, compared to a standard design approach.

How to predict building energy performance with low computational times and good reliability? The study answers this question by employing artificial neural networks (ANNs) to assess energy consumption and occupants' thermal comfort for any member of a building category. Two families of ANNs are generated: the first one addresses the existing building stock (as is), the second one addresses the renovated stock in presence of energy retrofit measures (ERMs). The ANNs are generated in MATLAB ® by using the outcomes of EnergyPlus simulations as targets for networks' training and testing. A preliminary ‘Simulation-based Large-scale sensitivity/uncertainty Analysis of Building Energy performance’ (SLABE) is conducted to optimize the ANNs' generation. It allows to identify the networks' inputs and to properly select the ERMs. The developed ANNs can replace standard building performance simulation tools, thereby producing a substantial reduction of computational efforts and times. This can allow a wide diffusion of rigorous approaches for retrofit design, which are currently hampered by the excessive computational burden. As case study, office buildings built in South Italy during 1920–1970 are investigated. Comparing the ANNs' predictions with EnergyPlus targets, the regression coefficient is between 0.960 and 0.995 and the average relative error is between 2.0% and 11%.

Design criteria for a residential nZEB in Mediterranean climate are discussed. The integrated design procedure focuses on the problem of a large number of available building variants concerning the building envelope. The aim is to search the ones that minimize winter and summer energy demand without compromising thermal comfort. The adopted methodological approach combines the use of dynamic energy simulation tool (EnergyPlus), based on a one-dimensional conduction finite difference solution method, and a constrained multi-objective optimization algorithm. For four cities (Madrid, Nice, Naples, Athens), several passive strategies are compared: thermal properties of the building envelope, adoption of phase change materials with different melting temperatures, cool roof solutions, several window/wall ratio values, some external and internal shading systems. The results allow to evidence that it is difficult to understand the best trade-off between summer and winter performance, by assuring high standard of thermal comfort when the aim is to reach NZEB objectives in Mediterranean climate. However, some guidelines are indicated, starting from the discussed results.

Nowadays the study of Net Zero Energy Buildings (NZEBs) is fundamental, because they are the main strategy to reduce the building energy demand and CO2-equivalent emissions. This paper analyses a case study concerning a multipurpose building located in Palermo (Southern Italy), and evaluates the benefits related to the use of an earth-to-air heat exchanger in a NZEB, in terms of energy saving and reduction of CO2-equivalent emissions, for a Mediterranean climate. The chosen building envelope is thermally performing. The HVAC system consists in fan-coil units connected to an air-to-water heat pump, and mechanical ventilation. The energy demand is reduced by an earth-to-air heat exchanger that pre-heats the ventilation outside air in winter and cools it in summer. The optimization of the heat exchange with the ground is a key-element to reduce the primary energy requirements and CO2-equivalent emissions, especially during summer. Moreover, this paper assesses the possibility to obtain a NZEB using only on-site renewable energy (on the roof of the building), with and without the earth-to-air heat exchanger. The energy analysis is carried out by means of a dynamic building simulation engine, namely EnergyPlus. In addition, a thermal performance and an environmental analysis are performed.

Public energy policies must support the deep energy retrofit of buildings in order to fight climate change and energy poverty. Assessing the impact of such policies is extremely important because the supported energy retrofit measures (ERMs) can ensure huge energy, economic and environmental benefits. However, the energy investigation of wide building stocks is very complex. This issue is here tackled by using and enhancing the methodology SLABE ('Simulation-based Large-scale uncertainty/sensitivity Analysis of Building Energy performance'), which conducts reliable analyses of energy retrofitting building categories. SLABE employs Latin hypercube sampling to generate Representative Building Samples (RBSs), which represent the energy behaviour of the explored building stock. Then, post-processing is applied to assess the impact of proper ERMs on energy consumption, polluting emissions and lifecycle costs. Thus, the cost-optimal retrofit solutions are found in absence and presence of financial incentives, respectively. The outcomes are exploited to assess the effectiveness of current energy policies and to propose potential improvements for harmonizing the public and private perspectives. The methodology combines EnergyPlus and MATLAB®. As case study, it is applied to the Italian office building stock. The outcomes show huge potential energy and cost savings as well as polluting emission reductions.

Zero-energy and zero-carbon buildings would be a huge opportunity for contrasting the climatic changes and, more in general, the deterioration of the microclimate inside and around cities. About it, a question appears compulsory: are zero-energy and zero-carbon concepts applicable at urban scale? This paper tries to answer to this question, by discussing the possible effects of the application of appropriate city planning techniques when a new settlement is designed. An integrated approach to urban planning is applied to a case study, for promoting the design of buildings with very low (or zero) energy needs, characterized by high indoor comfort conditions, by taking into consideration whole city areas, with different kinds of services. Passive heating, cooling and daylighting techniques have been combined, as well as the integration of renewable sources, in order to minimize the energy demand and environmental impact, for having a sustainable ‘urban balance’ and, in general, a sustainable urban growth. As real case study, the design of the holiday village ‘Olympiad’ is presented; it should be built in an unstructured seaside area in Greece. Several indexes are introduced to evaluate the global sustainability of the settlement, through the application of the definition of ‘on-grid ZEB’, with reference to each building as well as for the entire village. This kind of research could help city planners for a growth inspired to general goals of urban sustainability.

Efficient HVAC devices are not sufficient to achieve high levels of building energy performance, since the regulation/control strategy plays a fundamental role. This study proposes a simulation-based model predictive control (MPC) procedure, consisting of the multi-objective optimization of operating cost for space conditioning and thermal comfort. The procedure combines EnergyPlus and MATLAB ® , in which a genetic algorithm is implemented. The aim is to optimize the hourly set point temperatures with a day-ahead planning horizon, based on forecasts of weather conditions and occupancy profiles. The outcome is the Pareto front, and thus the set of non-dominated solutions, among which the user can choose according to his comfort needs and economic constraints. The critical issue of huge computational time, typical of simulation-based MPC, is overcome by adopting a reliable minimum run period. The procedure can be integrated in building automation systems for achieving a real-time optimized MPC. The methodology is applied to a multi-zone residential building located in the Italian city of Naples, considering a typical day of the heating season. Compared to a standard control strategy, the proposed MPC generates a reduction of operating cost up to 56%, as well as an improvement of thermal comfort.

The study proposes a comparison between the thermal performances of a real building, built according to the German standard DIN 4108-2:2003, and a refurbished one (in a theoretical investigation), aimed at satisfying the more restrictive requirements of the new version (i.e., 2013) of the same standard. The analysed building, completed during the 2012, is located in Berlin. The building has good performances in terms of energy demand for heating. Diversely, during the first years of operations, some overheating problems have been verified in summer. Because of sustainability motivations, cooling devices are not installed. An energy-oriented retrofit is here proposed, aimed at verifying if the fulfillment of the new version of the DIN 4108-2:2013 will produce better microclimatic conditions in summer. The results show the necessity of an accurate approach to the topic of summer thermal protection.

Dynamic insulation consists of building envelope components that are air-permeable. Presently, the scientific literature provides various studies on the achievable performance of this technology during the heating season and in steady-state conditions, showing energetic benefits due to the reduction of the walls' thermal transmittance. Diversely, this paper investigates the behavior of dynamic insulation under transient conditions and is focused on the cooling season. In this study, a numerical model is proposed in order to evaluate the profiles of temperature and water vapor concentration, as well as the heat and vapor fluxes through air-permeable walls. This model is implemented in a home-made MATLAB® code, which adopts a finite difference method (FDM), and validated by comparison with: I) a simple case study from an authoritative literature reference; II) a CFD model run in COMSOL®, which adopts a finite element method (FEM). Then, the code is used to explore the benefits induced by dynamic insulation on nocturnal free cooling. For this purpose, nocturnal free cooling potential is investigated in two cases: a) under the hypothesis of dynamic building insulation (i.e., airflow crosses the walls) and b) under the hypothesis of static insulation (i.e., the envelope is not air-permeable). The study shows the advantages of air flowing through the walls. In particular, a reduction of the indoor temperature is verified. The analysis is performed for three geographical locations (Cairo, Naples and Munich), characterized by different climates, in order to assess how the achieved benefits vary depending on the latitude.

A new analytical methodology aimed at characterizing the energy performance of new and existing buildings is proposed for both winter and summer and with reference to entire urban context, and the methodology is transferred into Geographic Information Systems (GISs). The main target is the evaluation of criticalities of the building stock, promoting effective design for new buildings and proper refurbishment of existing buildings. In this regard, the application of standardized procedures is too onerous if the goal is the qualitative distribution of the energy performances with reference to entire urban areas. The energy demands for space heating are evaluated by simplifying the methodology of the European Standard EN ISO 13790, while with reference to summer cooling, a new hybrid method has been specifically developed. The whole method was applied to the entire historical center of the Italian city of Benevento and, thus, to more than 500 buildings. Moreover, comparisons with measured/evaluated energy requests have been performed to identify the reliability of the methodology. Information on energy performances in the whole city center, moreover, allowed for the setting of “Urban Energy Maps,” a tool dedicated to local government, usable for advanced energy planning and territorial control in energy supply.

Building energy simulation programs – in most cases – solve heat conduction through walls by considering one-dimensional heat flows, neglecting thermal bridges. The paper shows a new method for implementing bi-dimensional and three-dimensional heat transfer in dynamic energy simulation software, allowing a great improvement of their capabilities. The new procedure starts from the theory of state space representation of transfer functions, and then introduces simplifications for reducing computational time and the required CPU sources. Starting from a first case study, aimed to verify the achievable correspondence of the simplified new method compared to the original one, two common thermal bridges have been deeply analysed, comparing the proposed methodologies and numerical solution based on using finite volume methods. The investigated building structures determine bi-dimensional heat flows because of discontinuities in both materials and geometry. By comparing the achieved outcomes to those derived by much more onerous CFD studies, several cases changing grid refinement, timestep, ambient condition and so on, the proposed method shows its suitability, with maximum errors never higher than 4.5%, also under hourly-variable outdoor temperature and solar radiation.

Thermal bridges are weak areas of the building envelope, determining heat flows higher than those characterizing the common dispersing surfaces (i.e., walls without discontinuities). This phenomenon induces uncontrolled thermal losses and hygiene problems, connected to the possible vapor condensation and mold growth. Presently, the numerical codes for the energy audits, as, for instance, EnergyPlus, carry out zero-dimensional (indoor air) and one-dimensional (conduction heat transfer) analyses, approximately estimating the thermal bridge effects on the seasonal heating demand of buildings. In this paper, results obtained by means of the simplified 1-D models are compared to those obtained by more sophisticated models 2-D or 3-D, in order to point out differences in terms of equivalent conductivity and thermal transmittance. Then, dynamic simulations compare the outcomes in terms of seasonal energy consumption. A typical office building has been considered, analyzing – according to three different approaches – the thermal bridge represented by the roof structure. The outcomes, with reference to several Italian climates, show that a proper modelling is necessary. In particular, an over estimation of the heat losses, determined by an approximate evaluation, induces higher cost of refurbishing, higher cooling energy requests in summer, minor thermal comfort in naturally ventilated buildings.

The European Energy Efficiency Building Directive 2002/91/CE, as well as other acts and funding programs, strongly promotes the adoption of passive strategies for buildings, in order to achieve indoor thermal comfort conditions above all in summer, so reducing or avoiding the use of air conditioning systems. In this paper, the energy performances achievable using an earth-to-air heat exchanger for an air-conditioned building have been evaluated for both winter and summer. By means of dynamic building energy performance simulation codes, the energy requirements of the systems have been analysed for different Italian climates, as a function of the main boundary conditions (such as the typology of soil, tube material, tube length and depth, velocity of the air crossing the tube, ventilation airflow rates, control modes). The earth-to-air heat exchanger has shown the highest efficiency for cold climates both in winter and summer. The possible coupling of this technology with other passive strategies has been also examined. Then, a technical-economic analysis has been carried out: this technology is economically acceptable (simple payback of 5–9 years) only in the cases of easy and cheap moving earth works; moreover, metallic tubes are not suitable. Finally, considering in summer a not fully air-conditioned building, only provided with diurnal ventilation coupled to an earth-to-air heat exchanger plus night-time ventilation, the possible indoor thermal comfort conditions have been evaluated.

Harnessing the appropriate radiative characteristics of buildings’ external surfaces is a highly effective way to reduce internal space heating and cooling demand. Building energy dynamic simulations are created in order to compare various external coatings with reference to a social housing case-study in a typical Mediterranean climate (Naples, Italy). An innovative index, the Surface Factor (SF) is proposed to inform the choice of the most suitable surface coatings as a function of local climatic conditions and thereby reduce overall energy demand. For cities with high solar gain and/or low winter degrees-day (SF > 0.65), high-reflective and/or high-emissive coatings (i.e. “cool paints”) are suitable, while low-reflective and/or low-emissive external coatings are more suitable for cooler climates (SF < 0.4). The simultaneous interactions of wall mass, surface radiative characteristics and indoor ventilation on the summer cooling energy demands are evaluated and substantial heating or cooling savings can be achieved, particularly for existing buildings. For regions in which outdoor night temperature is lower than the indoor value, high thermal inertia walls are viable only when coupled to night ventilation. Diurnal ventilation coupled to massive walls was found to be energy inefficient.

In the museum environment, the temporal stability and the spatial uniformity of the indoor microclimatic parameters are necessary primarily for the correct artwork conservation and then for the occupant thermal comfort. Therefore, a HVAC system is usually necessary. This paper above all emphasizes the integration of Building Energy Performance Simulation (BEPS) and Computational Fluid Dynamics (CFD) codes. This coupled numerical approach can provide accurate information about both the HVAC system energy request and the indoor microclimatic control (temporal and spatial distribution of the parameters). Then, a case study concerning a typical museum exhibition room is examined. The annual energy request for three types of all-air system, as well as the temporal variation of indoor temperature and relative humidity, is evaluated by means of a BEPS code. Energy savings can be obtained using a system with desiccant wheel (11%) or enthalpy wheel (9%), compared to the base system. As regards indoor relative humidity control, this is more critical for summer conditions, and the best performance is obtained by the system with desiccant wheel. Then, the spatial microclimatic control is analyzed by means of a CFD analysis, for various thermal load conditions and different air diffusion xequipments. The best performances are obtained by using the swirling (vortex) diffusers; also the perimetrical stripes of slot diffusers show satisfactory performances. Finally, in order to evaluate the ability of air diffusion equipments to assure good ventilation effectiveness, an analysis of the mean age of air is carried out too.

Indoor overheating risk and increased energy demand for cooling are becoming more and more frequent in the building sector of the Mediterranean area. In detail, for the reduction of the energy consumption of educational buildings, characterized by high endogenous gains, the particular boundary conditions affecting their use should be taken in consideration, and thus schedules of occupancy, wide necessity of air-changes for air quality. This paper, with reference to a case study, proposes deep investigations aimed at optimizing the annual energy performance of an educational building of the University of Sannio, located in the Southern Italy. A numerical model of the building has been designed and validated according to monitored data. Starting from the present scenario, after a complete refurbishment of the building envelope, the potentialities of several typologies of green roofs - by considering also the implementation of the adaptive approach in the comfort standard - have been tested. The scope is the optimization of the energy demand for the annual microclimatic control, by avoiding an energy-intensive operation of the air-conditioning devices during the warm season.

A novel methodology is proposed in order to support the cost-optimal design of building envelope’s thermal characteristics and space conditioning systems in presence of an enhanced simulation-based model predictive control (MPC) for heating and cooling operations. The cost-optimal solution is identified by running a main mono-objective genetic algorithm (GA) that allows to minimize the global cost for space conditioning over building lifecycle. Each solution investigated by the GA represents a building thermal design combined with the MPC of space conditioning systems. In order to define the MPC strategy, the main mono-objective GA launches two secondary bi-objective GAs that optimize the heating and cooling operations, respectively. These secondary GAs perform a Pareto optimization by minimizing operating cost for space conditioning and thermal discomfort. They provide the optimal values of hourly set point temperatures for heating and cooling systems, with a day-ahead planning horizon, by considering the forecasts of weather conditions and building use. The optimal control strategy is detected based on needs and wills of users, who set a minimum level of thermal comfort to be fulfilled. The three employed GAs are implemented by coupling MATLAB® (optimization engine) with EnergyPlus (building performance simulation tool). For testing purposes, the methodology is applied for the thermal design of a new multi-zone residential building located in Naples (Southern Italy). It produces potential savings of 35.4 kWh/m2a as for primary energy consumption, and of around 7’000 € as for global cost, by ensuring the same satisfying comfort level, compared to standard approaches for building thermal design and space conditioning systems’ control.

Hospitals represent the most energy-intensive buildings in most of the World, mainly because of strict requirements for micro-climatic control and high energy needs for equipment. Thus, the effective energy design and/or retrofit of these buildings can yield huge energy, environmental and economic benefits. In this frame, the study investigates the energy retrofit of a hospital building, i.e., the “D” Pavilion of the “A. Cardarelli” hospital facility in Naples (South Italy). The building is modeled in EnergyPlus and the energy model is calibrated by comparison against measured data, provided by an annual experimental campaign. Hence, in order to address building energy retrofit, a rigorous cost-optimal analysis is conducted by coupling EnergyPlus and MATLAB®. The investigated energy retrofit measures (ERMs) are addressed to the energy systems and to the exploitation of renewable energy sources. ERMs for the building envelope are excluded because they are not effective for the considered case study. The optimization allows to explore a comprehensive domain of retrofit scenarios, and thus, finally, robust cost-optimal solutions are found in correspondence of different discount rates. These solutions yield substantial reductions of primary energy consumption, global cost and polluting emissions with payback periods around 4 years.