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It is well known that in March 2020 a state of emergency was declared, due to the worldwide spread of the new SARS-CoV2 virus. Since that time, all nations have put containment measures in place to avoid a health and social collapse. The main ways of spreading the Covid-19 infection are close contact with an infected person, inhalation of respiratory droplets produced by an infected person and contact with infected surfaces. Part of the droplets produced by an infected person are so small that they are not affected by the force of gravity, so they remain in suspension forming the bio-aerosol. The method of transmission via bio-aerosol is a mechanism recognized by the World Health Organization (WHO), which in that case highlights the important role of mechanical ventilation of building rooms to reduce the risk of contagion. Starting from this assumption, the aim of the paper is to analyse various HVAC systems, evaluating which of these is more efficient to reduce the contagion from Covid-19, and to carry out an energy-cost analysis of the different proposals. To date, there are no legal obligations for the correct design of an air conditioning system capable of countering the spread of the infection from Covid-19. In this paper, the Walles-Riley model was used to derive the number of external air changes per hour needed to reduce contagion. This model can be used for diseases that spread by air. The analyses were conducted on an existing building of the public administration for office use in Southern Italy. The model was dynamically simulated and validated through energy bills. The HVAC systems analysed were fan-coils with primary air and radiant panels with primary air. The energy analysis was first conducted under standard conditions and then in conditions that counter the spread of the virus. An analysis of energy costs was also carried out to assess the increase in expenditure compared to standard conditions. The results show that the number of external air changes per hour necessary to drastically reduce the probability of Covid-19 infection is equal to 5 vol/h. Acting on the air conditioning system is useful to counter the spread from Covid-19 but requires very high energy consumption. A solution to this problem could be to couple the intervention on the air conditioning system with one or more interventions on the building envelope.

In recent years, the European Union has developed a sustainable, competitive, safe, and “decarbonised” energy approach. To achieve this objective, especially in highly urbanized contexts, there is a need to drastically improve the energy behavior of buildings and related energy systems. For this purpose, the aim of this paper is to analyse two very promising technologies that exploit the geothermal energy of the ground: the Earth-to-Air Heat eXchanger (EAHX) and the Ground Source Heat Pump (GSHP). These two systems are used as an energy retrofit strategy for the air conditioning system in an existing single-family house, located in Naples (south Italy). The building and the related systems are dynamically simulated using the DesignBuilder software. The results show energy savings of these two systems (compared to a traditional solution with an air-to-water heat pump) between 13% and 28%, with a total yearly primary energy consumption of about 80 kWh/m2 for the case with EAHX and around 67 kWh/m2 for the case with GSHP.

The theme of the energy requalification of historic buildings is addressed considering the Palaeontology Museum of Naples (Southern Italy). It is assessed whether, through non-invasive methods and without intervening on the building envelope, it is possible to obtain internal hygrothermal parameters suitable to allow both occupants’ thermal comfort and satisfactory conservation conditions for the archaeological finds. In addition, a relevant reduction of energy requirements and CO2 equivalent emissions is required. Dynamic energy simulations are conducted regarding both the current configuration and the various possible modifications concerning the air conditioning system; the model is calibrated by comparison with real energy consumption data. The electric and primary energy are compared for the various cases. Furthermore, the internal hygrothermal conditions for occupants’ thermal comfort and for conservation of the archaeological finds are analysed. Finally, the possibility of inserting a suitable and minimally invasive photovoltaic system is evaluated and an almost ‘Double Plus-Zero Energy Building’ is obtained.

The European Union introduced the concept of “Net Zero Energy Building” (NZEB) to promote competitive, sustainable, eco-friendly, and “decarbonised” cities. To these aims, mainly with reference to highly urbanized places, it is necessary to renovate existing buildings to achieve the NZEB target. Thus, this paper analyses the energy retrofit of an existing building considering two low enthalpy geothermal systems in the HVAC plants: the Ground-to-Air Heat eXchanger (GAHX) and the Ground Source Heat Pump (GSHP). These two plants are used in different retrofit strategies and compared from an energy, environmental and economic point of view. A dynamic simulation software based on EnergyPlus calculation engine is used. The results are very interesting and demonstrate how by using a low enthalpy geothermal plant, a very low value of primary energy requirement can be obtained (about 60 kWh/m2, i.e., −71% compared to the existing building, characterized by a gas boiler). Moreover, substantial savings on annual energy bills and reduction of CO2 emissions are obtained.

Photovoltaic (PV) systems are often used for the attainment of the NZEB (Net Zero Energy Building) target. The lack of sufficient roof area for the plant installation is, however, a common issue that limits the spread of this technology mainly in urban areas characterized by high density of buildings. This work evaluates the possibility of obtaining the NZEB target for residences and offices in Mediterranean area, using only “on site” PV systems, i.e., on the roof slab, considering different typologies of building. An in-depth analysis is provided for obtaining the building geometric parameters that would allow to establish, in the first stages of the design process and avoiding dynamic energy simulations, whether it is possible to achieve energy self-sufficiency for a certain building, taking into consideration the characteristics of the plans and the number of floors. The results show that, for the investigated square-based residential building, the energy self-sufficiency, and therefore the NZEB target, is obtainable up a maximum of 7 levels (6 levels for rectangular shape building, 5 for L and courtyard shapes), while, for another case study building intended for offices, the energy self-sufficiency is obtainable up to a maximum of 7 levels. For early design analyses about geometric characteristics and intended use of new buildings, it would be possible to use the results reported in this study to achieve a first evaluation of NZEB target attainment.

The External Thermal Insulation Composite System (ETICS) is one of the most common passive strategies to obtain energy savings in existing buildings. Despite previous studies dealing with ETICS durability in real building case studies or involving accelerated ageing tests in climatic chambers, little progress has been made in the knowledge of the long-term durability and energy efficiency of the system. In this work, following previous experiments on ageing cycles, different climatic chambers are used to accelerate performance decay by simulating the natural outdoor exposure to assess the thermal transmittance decay of a building wall. After evaluating through laboratory tests the decay of the thermal performances of grey expanded polystyrene sintered (EPS) and polyurethane, the results are applied to an existing building. The case study building is virtually located in three different Italian climatic zones and an evaluation in terms of thermal transmittance values and their influence on heating energy consumption is made by using the dynamic simulation software DesignBuilder. The results show no significant variations during ETICS service life; the thermal performances are reduced little over time and therefore there is an increase in consumption for building heating of about only 2% after a time t1 equal to 8 years. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Nowadays, environmental and energy issues attract a lot of attention in the civil buildings sector, leading to the emergence of new technologies and new targets, which include Net Zero Energy Buildings (NZEBs). However, despite the great response in scientific research, the spread of NZEBs in Europe is quite limited. This is due not only to the lack of transposition of the related European Directives into the various national legislations, but also to the high initial cost of such high-performance buildings. The aim of this paper is to demonstrate how different energy retrofit strategies on existing buildings can lead to the achievement of the NZEB target if encouraged by tax incentives, at zero or almost zero cost. The introduction of tax incentives by individual EU member states would allow the spread of NZEBs that are still underdeveloped, especially in highly urbanized contexts. A suitable building energy dynamic simulation software has been used. The case study refers to a villa located in Southern Italy and for which different energy retrofit strategies are proposed to reach the NZEB target. For each case, an energy and economic evaluation is carried out to evaluate the feasibility of the interventions, exploiting the so-called “Super-Eco-Bonus 110%” incentive. The main results highlight that among the various solutions, the greatest energy cost reductions are obtained with the use of heat pump generators. Furthermore, the solution with the biomass boiler allows the use of a smaller number of photovoltaic panels to meet the yearly energy balance of the NZEB.

The energy needs of a Net Zero Energy Building (NZEB) are fully met by renewable energy sources. These strongly depend on their characteristics and on meteorological-geographical factors, but also on different kinds of energy balance. The aim of this paper is to investigate the comparison between two different photovoltaic systems (fixed and tracking) and two kinds of energy balance (yearly and monthly), to evaluate which system better achieves the definition of NZEB for an existing residential building, so limiting exchanges with the national electricity grid. A dynamic energy simulation software (DesignBuilder) is used. The results show that the photovoltaic surface which attains the NZEB target on yearly basis not always achieves the same objective when the energy balance is performed on monthly basis. Furthermore, considering a monthly balance, the size of the photovoltaic system with biaxial solar tracking is 45% minor compared to the fixed photovoltaic system, thanks to a steadier energy production.

Earth-to-air (EAHX) and/or air-to-air (AAHX) heat exchangers can be conveniently inserted in heating, ventilation, and air conditioning (HVAC) systems to obtain relevant energy saving. In this article, the subject is analyzed for an office building located in two Italian localities: Milan (Northern Italy, with cold winters and hot summers) and Palermo (Southern Italy, with mild winters and very hot summers). A dynamic building energy performance simulation software is used to simulate a designed office building. The HVAC system is based on fancoils and primary air, with or without EAHX and AAHX. The seasonal analysis shows better energy results for AAHX in winter and EAHX in summer, respectively. The yearly analysis shows that the EAHX is preferable in hot or mild climates. Successively, the EAHX and AAHX are combined: based on the previous seasonal results, the first one is activated in summer, while the second in winter. The combination of the two technologies is preferable for Milan (energy saving up to about 75%) compared to Palermo (saving up to about 60%). Finally, the analyses of the equivalent CO2 emissions and discounted payback are reported.

In this paper, a model that analyses the coupling of a concentrating photovoltaic and thermal (CPV/T) system with a desiccant cooling (DC) system used to satisfy the energy loads required by a supermarket, is presented. A detailed analysis of the supermarket electrical and thermal loads is conducted in different periods of the year: summer, winter and half seasons. A CPV/T system linear focus configuration is considered, and its sizing as a function of the solar Direct Normal Irradiance (DNI) is realized for each period of the year. Hence, an Artificial Neural Network (ANN) is used to model carefully the DNI adopting experimental data in the simulation process. The coupling between the CPV/T and DC systems allows to obtain energy and economic savings during the year compared with a conventional solution, considering accurately in the modelling: supermarket energy loads, solar radiation, environmental conditions, etc. In particular, the analysis of three case studies is performed, where the main aim has been to size the CPV/T-DC integrated system and to study how it can match the different supermarket energy needs. The three solutions are analyzed from an energetic and economic point of view in order to demonstrate the effectiveness of the solution proposed.

This paper investigates air-to-air (AAHX) and earth-to-air (EAHX) heat exchangers, to reduce the energy requirements of air conditioning systems for office buildings. The AAHX considered is of static type with a partition wall and allows recovering both sensible and latent heat. The EAHX technology exploits the capability of the ground as energy storage, through a system of earthed air ducts laid horizontally. In summer, the ground usually presents temperatures lower than outside ventilation air temperatures, while in winter it could have, in some hours/days, a temperature higher than the outside air. Three European cities are considered: Palermo (southern Italy), with mild winters and very hot summers; Milan (northern Italy), with cold winters and hot summers; Berlin (Germany), with very cold winters and quite hot summers. The analysis is performed by means of EnergyPlus, a dynamic building energy simulation software, with reference to the same, newly designed office building, with or without heat recovery systems. The air conditioning system is based on fan-coils and primary air, and the EAHX (or the AAHX) is inserted in the first part of the primary air-handling unit. The research shows that in winter the use of the AAHX reduces the energy requirement much more than the EAHX, while in summer the EAHX is preferable. Moreover, the annual analysis shows that the use of the EAHX is more convenient in hot climates. The case of coupled heat exchangers (AAHX + EAHX) is also investigated. The evaluated discounted payback is about 6–9 years for the EAHX (3–5 years if an incentive of 20% is considered) and 1–3 years for the AAHX (less than 1 year with the incentive).

Delaying the analysis of the building performance to the final stages of the design process can often cause the actual results to differ from the expected ones, with the issue of significant redesign costs. The aim of this work is to improve the designer’s control on thermal and geometric variables of the building in the first stages of the design process, to obtain an optimized building from different points of view. An innovative computational performance-driven design optimization workflow is proposed. The integration of a parametric algorithmic modelling tool in a genetic algorithm powered performance optimization procedure allows to minimize energy need and construction cost of the building, and to optimize the natural illumination levels, affecting several geometric variables. This approach is tested on the early design stages for the new construction of an educational building located in the centre of Italy (L’Aquila). The results are post-processed in order to provide an innovative graphical visualization of the outputs to improve the decision-making process. Useful insights on the influence of different design choices on three key performance indicators can be drawn for the case study building, by comparison of the Pareto solutions: optimization results highlight the strongest influence of window-to-wall ratio, among the other variables, on energy need and useful daylight illuminance.

The costs of concentrating photovoltaic (CPV) and concentrating photovoltaic and thermal (CPV/T) systems are highly reduced in the last years because of their increasing diffusion. The unit power cost also depends on the plant size. Hence, the main aim of this paper is to analyze the feasibility of a CPV/T system adopted for users with increasing sizes located in Salerno (Italy): the house, the hotel, and the food industry. An experimental model was developed for an accurate evaluation of the electrical and thermal powers supplied by the CPV/T system when direct normal irradiation (DNI) and environmental temperature vary. A modular configuration of a line-focus CPV/T system was sized to match the electrical and thermal loads of each user. The current economic results, together with a forecast till the year 2025, were discussed. In 2025, for the same CPV system adopted for the domestic user, the net present value (NPVs) are expected to increase by 6.7% and 13% in pessimistic and optimistic scenarios, respectively, with reductions of its discounted payback period (DPBP) of 16% and 30%. For the same CPV systems adopted for the other two users, the NPVs are expected to increase by about 4.2% and 8.4% in pessimistic and optimistic scenarios, respectively, with decreases of its DPBP of 14% and 27%.

Highlights • Earth-to-Air Heat eXchanger uses geothermal energy for air conditioning systems. • A 2D mathematical model of the EAHX is developed to obtain the system performance. • A case study office building is analysed for eight worldwide localities. • Air temperature variation along the EAHX and EAHX efficiency are calculated. • Reduction of thermal capacity of the coils inside air handling unit is evaluated., A great fraction (20–40%) of primary energy is required for building air conditioning, so the use of renewable energy sources is increasing. The geothermal energy for Heating, Ventilating and Air Conditioning (HVAC) systems can be used considering an Earth-to-Air Heat eXchanger (EAHX). This work analyses the performance of an EAHX through a mathematical model (2D), as a function of diameter and length of the air ducts. The problem is solved with finite element method. A case study office building is analyzed. The air conditioning plant is characterized by fan-coil units and primary air; the EAHX is positioned upstream the Air Handling Unit (AHU) to pre-cool/pre-heat the air. The building is virtually placed initially in six Italian cities (different climatic zones according to Italian regulation DPR 412/93) and subsequently in eight worldwide cities according to Köppen climate classification. The following parameters are calculated: air temperature variation and thermal efficiency of the EAHX; the decreasing of cooling and heating capacity of the coils into the AHU. The best results refer to a duct length of 100 m for Ottawa (warm-summer humid continental climate, 65% capacity reduction), the worst ones for Rio de Janeiro (tropical wet and dry climate, maximum 24% reduction).

In this paper the energy performances carried out by an investigation conducted on a Heating, Ventilation and Air Conditioning (HVAC) system, composed by an Air Handling Unit (AHU) for the primary air coupled with a horizontal-pipes Ground-to-Air Heat eXchanger (GAHX) and fan-coil units, for an office building, supposed to be placed in four different cities (Rio de Janeiro, Dubai, Naples, Ottawa) belonging to four different worldwide climatic areas, according to the K&ouml, ppen climate classification. The investigation is performed by means of a two dimensional numerical model, experimentally validated, of an GAHX solved with finite element method. The results introduced in this paper are carried out by varying the length of the pipes and the air flow velocity, thus, also the number of tubes forming the GAHX is varied since the volumetric flow rate to be provided to the AHU must be kept constant. The energy performances of the above-mentioned HVAC system are analyzed, both in summer and in winter operation modes. Specifically, the reduction of the power of the heating and cooling coils in the AHU due to the pre-treatment of the air operated by the GAHX, the efficiency of the GAHX and the inlet-outlet temperature span are evaluated through a sensitivity analysis. These results lead to say that an GAHX for the geothermal pre-treatment of the air to be introduced into the AHU is energetically very convenient since it leads total thermal power savings in all the investigated cities, that makes this solution competitive. Specifically the best value of power reduction (61.5%) for a 100 m pipe-length GAHX is obtained in Ottawa, a city belonging to continental climate zone. The worst results in terms of power reduction are registered in Rio de Janeiro, a city belonging to the tropical or equatorial climates: this reduction, for a 100 m pipe-length ground to air heat exchanger, is 23.9%.

The increasing energy demand encourages the use of photovoltaic solar systems coupled to organic rankine cycle (ORC) systems. This paper presents a model of an ORC system coupled with a concentrating photovoltaic and thermal (CPV/T) system. The CPV/T-ORC combined system, described and modeled in this paper, is sized to match the electrical load of a medium industrial user located in the South of Italy. A line-focus configuration of the CPV/T system, constituted by 16 modules with 500 triple-junction cells, is adopted. Different simulations have been realized evaluating also the direct normal irradiance (DNI) by means of the artificial neural network (ANN) and considering three input condition scenarios: Summer, winter, and middle season. Hence, the energy performances of the CPV/T-ORC system have been determined to evaluate if this integrated system can satisfy the industrial user energy loads. In particular, the peak power considered for the industrial machines is about 42 kW while other electrical, heating or cooling loads require a total peak power of 15 kW; a total electric average production of 7500 kWh/month is required. The annual analysis shows that the CPV/T-ORC system allows satisfying 100% of the electric loads from April to September; moreover, in these months the overproduction can be sold to the network or stored for a future use. The covering rates of the electrical loads are equal to 73%, 77%, and 83%, respectively for January, February, and March and 86%, 93%, and 100%, respectively for October, November, and December. Finally, the CPV/T-ORC combined system represents an ideal solution for an industrial user from the energy point of view.

A passive strategy to reduce the energy consumption of existing buildings is to improve the thermal insulation of the opaque building envelope and insert windows with low thermal transmittance U. But what is the best compromise between cost of intervention and reduction of primary energy? The aim of this paper is to answer this question using the innovative cost-optimal methodology and a dynamic energy simulation software. The case study refers to an existing school in central Italy. Eight passive strategies are analysed, combining different insulation thicknesses and types of windows. Furthermore, a comparison between cost-optimal methodology and discounted payback analysis is reported. Finally, a sensitivity analysis on parameters influencing the cost-optimal method is conducted. The lowest primary energy is obtained considering an insulation thickness of 12 cm and windows with U of 1.10 W/m2 K, while the best case using the cost-optimal methodology refers to a low increase in insulation thickness.

A new concept of building is represented by Zero Energy Buildings (ZEBs). This paper evaluates the possibility to obtain a NZEB (for office building) by using only “on-site” renewable energy, solely on the roof. A dynamic energy simulation code, EnergyPlus, is used. Two different Italian climatic zones (Palermo and Naples) and two typologies of building are considered: square or rectangular basis. For the building with square basis, the energy self-sufficiency is kept up to a higher number of the building levels (8 for Naples, 10 for Palermo) compared to the case of rectangular basis (7 levels for Naples, 9 for Palermo).

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.

In school buildings, the relationship between energy requirements and occupant thermal-hygrometric comfort plays an important role because these buildings are great energy consumers also as the current rules impose large rates of ventilation outside air for classrooms. The goal of this paper is the thermal and energetic comparison of various air-conditioning systems that are appropriate for school buildings. Among the different suitable HVAC systems for schools, the following types are considered: All-Air system (with constant air volume and heat recovery) and zone heating coils; radiant heating floor panels and primary air; fan-coils and primary air. The analyses are performed on a designed new school building, by means of a dynamic building energy simulation software (Design Builder), based on Energy Plus engine. The simulations are conducted to obtain the trends of various internal environmental parameters for both winter and summer, i.e.Temperature, relative humidity and PMV (Predicted Mean Value) index in one classroom. In cooling and heating conditions, the HVAC systems are active, while in the intermediate seasons only mechanical ventilation is working. This study evaluates the performances of different HVAC systems from an energy, thermal comfort and economic point of view. The analyses are conducted for Rome, characterized by Mediterranean climate.

At present, the office buildings built in Italy before the first energy regulations of the '70s show a growing energy consumption for heating and cooling. The electrical energy demand for summer cooling is increasing, too. Among the possible strategies, thermal insulation of the building envelope is a common solution to reduce energy needs. However, in buildings with high internal thermal loads and/or located in climates characterized by warm summers and mild winters, an excessive insulation thickness, although in compliance with legal requirements, may be counterproductive. In this paper, by using a dynamic energy simulation software (Design Builder), a case study is analyzed concerning the energetic and economic impacts of thermal insulation applied on the external side of an existing office building. The chosen Mediterranean localities are Palermo, Rome, Milan and Cairo. Increasing internal thermal loads (10, 20, 30 W/m2) are considered. The results show that hyper-insulation of buildings is not convenient in the considered climates. In two localities (Palermo and Rome), the optimal insulation thickness is lower than that needed to meet the regulations on energy saving in buildings. Finally, PMV (Predicted Mean Vote) index for some disadvantaged rooms is shown to consider also the thermal comfort requirements.

Attualmente gli edifici adibiti ad ufficio costruiti in Italia prima dell’entrata in vigore delle prime leggi sul contenimento del consumo energetico degli edifici (L. 373/76) sono caratterizzati da un crescente consumo di energia per il riscaldamento in inverno e per il raffreddamento estivo dei locali. È soprattutto in crescita significativa la domanda di energia elettrica per il raffreddamento. Tra le possibili strategie per ridurre le richieste energetiche degli edifici, l’isolamento termico dell’involucro edilizio è una soluzione frequente. Tuttavia, in edifici con elevati carichi termici interni e/o situati in climi con estati calde ed inverni miti, un eccessivo spessore di isolante può risultare energeticamente penalizzante, sebbene in linea con gli attuali limiti di legge. In questo articolo è analizzato un caso di studio, sviluppato con un software di simulazione energetica dinamica (Design Builder), che riguarda l’impatto energetico ed economico dell’isolante termico applicato sul lato esterno di un edificio esistente adibito ad uffici. Le località scelte in ambito mediterraneo sono Palermo, Roma, Milano e Il Cairo e come carichi termici interni sono considerati 10, 20 e 30 W/m2. I risultati mostrano che uno spessore eccessivo di isolamento termico degli edifici non è conveniente nei climi più caldi. Inoltre, per due località (Palermo e Roma), lo spessore ottimale di isolante è minore di quello necessario a soddisfare i requisiti legislativi attuali sul contenimento dei consumi energetici negli edifici. Infine, è stato valutato anche l’indice PMV (“Predicted Mean Vote”, cioè voto medio previsto) in alcuni ambienti svantaggiati, per tener conto anche del comfort termico degli occupanti.

In historical centres, the buildings are characterized by pitched roofs, sometimes not insulated, with low thermal inertia and coated in brick tiles with low solar reflection factor. So, the attics show high energy costs for heating and cooling. This paper analyses the energy saving obtainable by applying innovative surface finishes on interior and exterior surfaces of opaque envelope components of existing buildings. This simple and inexpensive retrofit action determines energy cost reductions for heating and cooling, but also benefits regarding indoor thermal comfort and useful life of buildings, because condensation problems and thermal shock are reduced; moreover, it preserves the architectural and chromatic characteristics of the building envelope. The analysis is performed by means of a building energy simulation code, considering typical HVAC systems for various Italian and European cities. A technical-economic and environmental investigation is also performed. Thermal energy needs of buildings for summer cooling can be reduced up to 60% by applying “cool paints” on the external surface of walls and roof, while internal low infrared emissivity coatings can reduce winter thermal requirements up to 12.5%. Significant primary energy savings for heating and cooling and reductions of greenhouse gas emissions (up to 60%) can be obtained, as well as a payback value of few years in most cases.

The effectiveness parameters of desiccant wheels depend on the variable operating conditions. Experimental data measured in an air handling unit equipped with a desiccant wheel and data provided by the manufacturer software are used in the present work to investigate the dependence of effectiveness parameters on the rotation speed. The air handling unit belongs to a test facility with a microcogeneration system. The regeneration airflow is heated up to moderate temperatures in the range 45–70 °C by using thermal energy produced by the microcogenerator and/or a boiler. The analysis of the results shows that i) the manufacturer software tends to underestimate the increase of process air temperature and to overestimate the dehumidification capability of the desiccant rotor compared to experimental data; and ii) the various investigated effectiveness parameters present different dependences on the rotation speed: monotonic dependence, a maximum value for an intermediate rotation speed, and a negligible dependence.

This paper investigates the best strategies to reduce the energy requirements of air conditioning systems for office buildings by using two different types of technology: Air-to-Air (AAHX) and/or Earth-to-Air (EAHX) heat exchangers. The AAHX considered is a static type of heat recovery with partition wall, which allows recovering both sensible and latent heat by means of convection and conduction mechanisms via partition wall. Referring to EAHX, this technology exploits the capability of the ground as energy storage, through a system of earthed air ducts laid horizontally. In summer, the ground usually presents temperatures lower than outside ventilation air temperatures, while in winter it could have, in some hours/days, a temperature higher than the outside air. In the examined case, the air conditioning system is based on fan-coils and primary air, and the EAHX (or the AAHX) is installed upstream of the primary air-handling unit. The performance of the two examined technologies are analysed for three European cities with different climates: Palermo (Southern Italy), with mild winters and very hot summers; Milan (Northern Italy), with cold winters and hot summers; Berlin (Germany), with very cold winters and quite hot summers. The analysis is performed by means of EnergyPlus, a dynamic building energy simulation software, with reference to the same designed new office building with or without heat recovery systems. The research shows that, for all the analysed climates, in winter the use of the AAHX reduces the energy requirement much more than the EAHX, while in summer the EAHX is preferable. Moreover, the annual analysis shows that the use of the EAHX is more convenient in hot climates. The case of coupled heat exchangers (AAHX+EAHX) is also investigated. A further analysis is performed on the benefits that the two analysed technologies allow in different seasons.

Energy consumption for heating and cooling of Italian office buildings is growing. In particular, there is an increase in the demand for electricity for cooling in the summer. Thermal insulation on the external side of the buildings is a very usual strategy to reduce energy demand for air-conditioning systems. However, a too high thickness of insulating material, even if complying with current legislative requirements, can be disadvantageous in buildings characterized by great internal thermal loads and/or located in climatic contexts with mild winters and hot summers. In this paper, the energetic and economic influence of external thermal insulation is evaluated by using energy simulations under dynamic conditions (DesignBuilder software) for a case study. The analysis is performed for various cities (Palermo, Milan and Cairo) and for different values (10, 20, 30 W/m2) of internal thermal loads. According to the recent and innovative “cost-optimal” methodology, optimal insulation thicknesses are derived, and the results demonstrate the need to avoid excessive insulation of buildings to obtain the highest energy saving. Finally, an integration of the “cost-optimal” methodology is proposed considering also the topic of thermal comfort; this modification allows to obtain other optimal solutions compared to the basic calculation procedure.

Desiccant-based HVAC systems are nowadays a convenient alternative to conventional systems based on dehumidification by cooling, because they allow the reduction of equivalent CO2 emissions, electric peak loads and black-outs, as well as energy savings, interesting payback periods in several cases, better indoor humidity control and air quality, separate control of thermal sensible and latent loads. Their coupling with small scale natural gas-fired cogenerators is also suitable as thermal energy required for desiccant regeneration can be conveniently recovered from the microcogenerator. In this paper, the main improvements of an innovative desiccant-based HVAC system, located in Southern Italy (Mediterranean climate), are presented. To this aim, three different desiccant system configurations are experimentally analysed, while a conventional HVAC system based on dehumidification by cooling is evaluated by means of numerical approach. Firstly, the primary energy savings (up to 20–25%) and the reductions of equivalent CO2 emissions (up to 40–50%) of the desiccant systems compared to the conventional one are calculated when considering chillers with different energy efficiency ratio values. Successively, the above mentioned indices are evaluated as a function of the effectiveness of the heat exchanger and the cooling air humidifier installed in the proposed desiccant system configuration: primary energy savings up to 25–28% and reductions of equivalent CO2 emissions up to 35–40% are obtained.

Significant attention is currently being paid to reducing building energy demand and improving indoor thermal conditions, as required by European directives. In school buildings, a significant part of the winter energy demand is related to high airflow rates required for ventilating classrooms. Moreover, the correlation between comfortable indoor thermal-hygrometric conditions, healthy indoor air quality and satisfying student performance is well known. Few research works have investigated different types of air conditioning systems for typical school buildings, from the point of view of both energy and thermal-hygrometric performances. This kind of analysis is carried out in this paper. A typical school building located in southern Italy is analysed by using dynamic building energy simulation software. Different types of heating, ventilation and air conditioning (HVAC) systems are simulated for both winter and summer conditions. Indoor air temperature, relative humidity and predicted mean vote values are evaluated. The annual energy requirements, energy costs and related emissions are calculated. Finally, a multi-criteria analysis for the examined HVAC systems is proposed, considering different weighting for the main performance criteria (winter thermal comfort, plant costs, energy costs and emissions), in order to support decision making.

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.

Hybrid desiccant HVAC systems have shown several advantages, compared to conventional cooling and dehumidification systems. Therefore, their use is also spreading for tertiary and residential buildings, especially when the regeneration of the desiccant can be obtained by using available waste heat. In this paper, an experimental analysis is presented on the performances of a silica-gel desiccant wheel, inserted in a test facility characterized by an advanced desiccant air handling unit, coupled to an electric chiller, a natural gas-fired boiler and a small scale cogenerator. The desiccant wheel is regenerated by using low temperature thermal energy recovered from the microcogenerator. The effects of the main thermal-hygrometric parameters (outdoor air humidity ratio and temperature, regeneration air temperature) on the desiccant wheel performances have been experimentally evaluated; in particular, the thermal-hygrometric properties of the process air exiting the rotor and the desiccant wheel effectiveness values have been obtained. Finally, fixing the regeneration temperature at its maximum available value (65 °C), ventilation and internal latent loads that the desiccant wheel can handle have been evaluated and compared to the required values, both for a set of cities all over the world and as a function of the thermal-hygrometric outdoor conditions.

In the Mediterranean area, the increasing demand of summer cooling in residential and tertiary sectors is usually satisfied by electrically-driven units; this often determines electric load peaks and black-outs. Thus, a wide interest is spreading in small scale natural gas-fired polygeneration systems: a prime mover drives (mechanically, electrically, thermally) electric generators and/or heat pumps, desiccant wheels, etc., matching thermal (heating and cooling) and electric end-user requirements. In this paper, laboratory tests have been considered to experimentally evaluate a small scale polygeneration system based on a natural gas-fired Micro-CHP and a desiccant-based HVAC system. Cogenerated thermal power is used for the desiccant wheel regeneration, while electric power for auxiliaries, chiller and external units. The HVAC system can also interact with electric and thermal separate “production” systems. The main results of the experimental tests are shown, stating the increase of the COP of the chiller in desiccant-based HVAC systems. Then the paper identifies the operating conditions (outdoor and supply air thermal-hygrometric conditions, electric grid efficiency and partial load operation of the MCHP) which guarantee significant primary energy savings (up to around 30%) and CO2 equivalent emission reductions (up to around 40%) of the polygeneration system compared to the conventional HVAC system.

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.

The growing interest in Italy for its cultural heritage and the necessity for better conservation usually require that museums be provided with appropriate HVAC systems. Control of indoor relative humidity must ensure that the vapour transfer between the materials and the ambient is such as to avoid mechanical, chemical and biological damage. Thus, it is necessary to balance the main thermal loads, that one due to the occupants in exhibition areas, subject to rapid change and directly proportional to the degree of overcrowding, and thermal load related to outdoor air. A case study concerning a simulated modern museum is presented in this paper. Using the dynamic simulation code DOE 2.1 E and hourly climatic data (TRY), the operating costs of different all-air systems (also with dehumidification by adsorption) have been evaluated for exhibition areas and stock spaces, as well as system performance in controlling thermal-hygrometric ambient parameters.

A great portion of the global energy consumption depends on existing buildings. So, energy saving and related CO 2 emission reduction are important measures. This paper analyses the incidence of innovative surface finishes on the cooling and heating energy demand of existing buildings. These easy and cheap measures preserve the little living spaces, limited height and the architectural/chromatic characteristics. The analysis is conducted for various European cities, by using a dynamic energy simulation software. The primary energy required by the HVAC systems on seasonal and annual basis is evaluated and relevant energy saving (up to 21% on annual basis) is obtained. Finally, a technical-economic analysis is performed and interesting payback values are obtained (2.5-11 years in the best cases; 2–10 years, when a tax deduction of 35% is considered).

In order to deliver the European energy and climate objectives to 2050, significant changes are essential in the building sector, especially regarding the existing stock. Indeed, there is a huge potential for action, also regarding historic buildings. In this regard, today the question is: how to combine the building protection requirements and the application of energy efficiency measures? This paper tries to answer, evaluating if the refurbishment of historic architectures, in order to achieve very low energy need, is possible and economically feasible. More in detail, the applicability of the cost-optimal methodology (EPBD Recast 2010/31/EU) for historic buildings is discussed, by adopting the macroeconomic perspective, in order to take into account of the energy, environmental and economic impacts of about 60 packages of energy efficiency measures. The study is aimed to introduce a methodological approach to define reference buildings for historic architectures, through in-situ investigation of structural and energy peculiarities and, as real case study, the refurbishment of an Italian building of the XV century is presented. Moreover, guidelines are proposed to properly select energy efficiency measures, according to a point of view of cost-optimality. Conservation, aesthetical requirements, structural and energy issues are considered, as well as the incidence of all economic factors.

Regarding techniques used to evaluate daylighting illuminances, recent years have seen a steady increase in the use of computer programs, owing to increased computer speed and memory capacity. Despite a rise in the amount of available daylighting data, even the latest programs on the market only use standard CIE and IES sky models; besides, input climatic data and calculation procedures used by these programs do not always lend themselves to easy comparison: consequently, in the presence of different results from the programs, it is not always clear which parameters are responsible for these differences. From what has been said above and in order to examine closely various daylighting problems, we can better understand the need to develop a software tool to analyse the influence exerted by the choice of different parameters and calculation models on final results. As regards the various daylighting components (direct-from-sky, direct-from-sun, internally-reflected and externally-reflected), this paper is concerned with the direct-from-sky component, since it is essential for the internally-reflected component calculation. In particular, the procedure which has been developed calculates the direct-from-sky illuminance component on the work plane and on the other interior surfaces that make up the room. Exterior illuminances on unobstructed horizontal and vertical surfaces are also calculated, because they are necessary for the calculation of the externally-reflected component and useful for the reliability evaluation of simplified methods for the calculation of interior illuminances (daylight factor method and lumen input method). The computer program, named De-Light, has been developed in Visual Basic, an object-oriented program language, in order to obtain the greatest flexibility in input and output procedures. In this paper, following a description of the program, we compare the results obtained by De-Light with those obtained by two of the most common and reliable daylighting computer programs, Superlite 2.0 and Lumen Micro 7.1.

The economic analysis for running two kinds of hybrid air conditioning systems: all-air and air-and-water, both with add-on evaporative cooling stages, is studied in this paper. Single-duct, single-zone, constant volume systems are dealt with. Processing the climatic data of the European 'test reference year-TRY' for Italy, a comparison of such systems' performance versus the relative traditional one is performed. Energy consumption and operating costs are evaluated by an appropriate computer code written with the aim of: (i) making plain the input/output of data; and (ii) displaying very friendly software masks as well as useful graphical elaboration. On the basis of outdoor air state, calculations are performed according to two different procedures: (a) hourly, following the TRY profile; and (b) for each bin, 1 °C wide, in which the simultaneous dry- and wet-bulb temperatures fall.

In this paper we present work involving the processing of climatic data relating to some Italian cities, taken from a set of data known as European ‘test reference year’ (TRY). We aim to make a critical comparison of the thermohygrometric conditions of outdoor air in the summer season thus obtained with those design conditions as laid down by Italian regulations (UNI 10339) and with those recently suggested by ASHRAE. Subsequently, and with reference to some traditional and recent applications in the field of air-conditioning, we report on how performance differs according to outdoor summer thermohygrometric design conditions, such as those indicated by UNI 10339, by ASHRAE and by the processing of TRY data. Finally, we discuss the optimal choice of design conditions according to the type of application. Copyright © 2000 John Wiley & Sons, Ltd.

Daylighting as a key element in quality assessment of the built environment has led to an increasing interest in its corollaries, and in its integration with artificial light sources in interiors. The use of daylighting requires a knowledge of the sky luminance distribution since work plane illuminances and interior surface luminances depend on this. In this paper the recommendations of the Commission Internationale de l'Eclairage regarding sky luminance distribution measurements are reported, along with a survey of measurement techniques used to date. There follows a detailed description of videography, considering the principal system components, and finally some considerations relating to its possible application in this area are discussed.