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Nowadays the control of indoor healthiness and comfort has become a key issue in school environments. Indoor environment quality (IEQ) as regards indoor air quality (IAQ), ventilation requirement as well as health effects assessed by Hazard Index and Cancer Risk were investigated in a naturally ventilated school by monitoring indoor/outdoor CO2 concentrations and particulate matter (PM) levels. This way, a CO2 fluxes balance permitted to calculate actual ventilation rates used to classify the classrooms on the basis of the proposal contained in fpEN 16,798 standard. The relationship between ventilation, CO2 levels and PM was also studied. In absence of appreciable internal pollution sources, the indoor concentrations of chemical pollutants were correlated to the corresponding outdoor concentrations by the comparison of indoor/outdoor PM whose differences in this case depend only by indoor deposit and resuspension. Heavy metals (As, Cd, Ni, Pb) and PAHs were considered as required by CEN recommendations. A simple procedure was carried on to assess the potential health hazards of pollutants on students. Hazard Index and the total Cancer Risk of the inhalation exposure were evaluated as proposed by United States Environmental Protection Agency. The calculated values resulted normally acceptable if related to daily school period, but not completely satisfactory because they highlighted that the indoor contaminant concentrations were not acceptable for 24 h exposure. Therefore these chemical pollutants reduce the no health hazard exposure capacity of the children in the remaining part of the day.

Strong ventilation increments are currently suggested for containing the airborne diffusion of COVID-19 in indoor environments. However, it can involve an unacceptable growing of energy consumption. Therefore, maximum care must be addressed to improve efficiency of ventilation heat recovery (VHR). For this purpose, this paper investigates the opportunity of a technical solution. Consisting in adding downstream of the most diffuse heat recuperator, a heat pump using exhaust air as a cold source. An autonomous high efficiency air handling unit (HEAHU) was modelled for a school application. By simulation a performance comparison was carried on with two alternative systems based only on an exhaust air heat pump (EAHP) or on a heat recuperator for different weather conditions. Results indicated that the milder climate strongly penalizes heat recuperator and this fact deeply influences the conclusions. HEAHU saving compared to energy consumption of only heat recuperator is between 31% and 46%. For EAHP this saving varies from 2.5% to 48%. Only with a milder climate, EAHP presents a lightly greater saving than HEAHU. Heat pump technology looks to be very performing to foster the efficiency of VHR, especially in presence of high ventilation rates.

Graphical abstract, This study investigates the possibility to contain COVID-19 contagion in indoor environments via increasing ventilation rates obtained through high energy efficiency systems combining thermal recovery by heat exchanger and thermodynamic recovery by heat pump. The starting point of this assessment is a procedure to evaluate in naturally ventilated environments, the current infectious risk by using measurements of indoor/outdoor CO2 concentrations to calculate actual air changes per hour. The method was applied to some typical school environments in Italy. The results indicated very infectious situations with reproduction number Ro values up to exceed 13. But, the simulations assessed an extraordinary reduction of indoor viral concentration and consequently of the infection risk by a strong mechanical ventilation. High ventilation rates make facemasks effective even with use levels (from 50%) reasonable also for pupils. This way, R0 goes down the value one. As regards energy performance, the behavior of an autonomous high efficiency air handling unit (HEAHU), to be installed in an existing naturally ventilated classroom, was simulated in the monitored days. The results highlight the ability to achieve a reduction in energy consumption between 60% and 72%.

Variable speed drive (VSD) technology can be introduced in heating, ventilation and air conditioning (HVAC) systems, normally sized for peak load conditions, to match actual load requirements. The paper presents a detailed assessment of the impact of the application of VSDs to HVAC components in a public building. The study was based on the data provided by a long term monitoring of the performances. As regards the electricity consumption of pumping and fans, the investigation has pointed out the achievement of a global annual energy saving of 38.9% in comparison with the alternative of a constant speed HVAC system.

The thermo-hygrometric treatment related to the air change in buildings requires a relevant quota of the total energy demand of HVAC systems, especially when the ventilation demand is significant. A correct energy saving strategy therefore should always focus on the use of suitable techniques to reduce this energy consumption. As proved by the modern theories on comfort, less strict values can be accepted for the internal humidity set points without compromising indoor comfort conditions. In addition, Demand Controlled Ventilation (DCV) gives the opportunity to reduce energy requirements. This paper investigates the opportunities offered by the installation of a DCV system and a Building Management System (BMS) able to perform long term monitoring of the HVAC system in a real case study. This refers to a historic building in Venice in the area of the harbour and recently transformed into a modern university facility. Starting from the experimental data recorded by BMS, an optimization of the control strategies and simple tuning actions of the DCV controller were possible. Results validate the use of more flexible set points of indoor relative humidity and long term on-line tuning even in absence of self-learning control systems, as well as they highlight the achievement of remarkable energy savings thanks to these actions. The research demonstrates the fundamental contribution of successive control performance assessments by long term monitoring to individuate possible weaknesses in DCV system management.

Refurbished buildings should also increase their energy efficiency, according with current regulation; however, in case of historical buildings, preservation orders are so strict to hamper usual energy efficient interventions on the building envelope side. As a consequence, in historical buildings, HVAC (Heating, Ventilation and Air-Conditioning) systems and control strategies should be further improved, since they are the only true means for energy efficiency. This paper presents the set of technologies implemented in the frame of the refurbishment of an historical building in the very center of Venice, in order to lower energy consumption and increase occupants’ comfort. The refurbishment consisted mainly in the application of the following technologies: Surface Water Heat Pump (SWHP), Demand Controlled Ventilation (DCV) and trigeneration. Furthermore, the paper proves the achieved energy savings by comparing the actual energy consumption against detailed building energy simulations for baseline HVAC system configurations. For such a purpose, the authors take advantage of the installed extensive building management system (BMS), which is able to record detailed data about flow rates (of air and water), temperature and humidity for all of the key devices of the HVAC system. The building used as a case study is very significant because of its energy intensive intended use as well as for the very strict preservation orders acting on it. In particular, global primary energy savings equal to 36% have been calculated, if compared with a traditional baseline HVAC system.

The United Nations as well as the European Union are strongly committed in promoting a transition towards more sustainable and resilient cities. Indeed, they are increasingly affected by different types of threats, among which the natural ones such as earthquakes, fires, and floods (shocks) and climate variability (stresses). Cities are quite often unable to cope with the adverse effects of such natural hazards. This circumstance leads to the need of introducing resilience-related criteria (besides commonly used sustainability indicators) in decision-making processes. This paper investigates at which extent the inclusion of such new indicators, within multi-criteria assessment tools for supporting the decision-making process by Public Administrations, modifies the prioritization processes of a given set of planned actions to be implemented in cities, which are based instead on the above-cited commonly used indicators. The outcomes of the analysis demonstrated that the introduction of resilience among the prioritization criteria significantly modifies the list of priorities established using only sustainability indicators.

Resilience represents a new important feature that the anthropic systems, and cities among them, are called to cope with. In fact, the increasing negative stresses to which urban contexts are exposed, and mainly the climatic pressures, call for the capability of adapting to these modifications and, possibly, to restore the ex-ante situations. The role of the buildings and their envelope components is of crucial importance to this aim. This paper analyses the features of resilience of the roofs of buildings by means of proper quantitative indexes. On purpose, the performances of green and cool roofs are compared. The possibility of adopting nonstructural solutions, like the windows shading devices, is also considered.

This paper deals with the behaviour of battery-supported residential photovoltaic (PV) systems connected to smart grids, with a special focus on the interface with electricity distributors. In particular, this paper is aimed at the assessment of the benefits resulting from two predictive control strategies managing the charge of the electrochemical storage unit, in comparison with the conventional control strategy and applied to various combinations of photovoltaic system and battery pack sizes in a parametric analysis. The proposed control strategies dispatch electricity to the battery pack or national grid depending on the state of charge and differ in the shape of the profile of exported electricity, hence adapting to different interface profiles required at the electricity distributor’s side. In particular, the research shows that, by the proposed control strategies, the frequencies of occurrence of high values of exported electricity may be decreased by almost 100%, whereas medium-high values of exported electricity by 50%. Moreover, both of the control strategies are shown to be able to lower the yearly quadratic effective imbalance coefficient by around 15% in case of PV systems sized for Zero Energy Buildings (ZEBs), thus showing opportunities in the mitigation of electricity grid stresses from PV systems.

This article presents the economic performance of battery-supported residential photovoltaic systems connected to smart grids in the presence of a market-driven electricity tariff. In particular, the article deals with the economic benefit resulting on varied photovoltaic system and battery sizes, through a parametric analysis. Such an analysis is strongly dependent on the costs of photovoltaic systems and battery packs, which are prone to decrease in the coming years, according to many authors. In this context, the article investigates current and forecast economic scenarios, in order to show the expectable improvement in the financial performance in systems installed in the next few years. For this purpose, the article includes a review of photovoltaic system and battery prices forecasts for the coming years. The financial analysis takes into account two different (and conservative) feed-in tariffs: in the first case, the hourly national price of electricity is used as a feed in tariff, in the second ca...

In cities vegetated roofs are becoming more popular because they can mitigate Urban Heat Island phenomena by decreasing the outdoor air temperature in summer. This decrease reduces the electric energy demand for climatization of buildings, which, in front of a milder climate, will recur less to mechanical tools for guaranteeing thermal comfort conditions to occupants. Cities can registered another indirect positive effect: the reduced cooling energy demand, limits the heat released by the climatization systems’ external unities toward the urban open spaces, thus lowering the outdoor air temperature. Therefore, the outdoor surface temperature of green, as well as cool roofs, can be assumed as an important design parameter for guaranteeing the sustainability of buildings and their approach toward an nZEB path. Obviously, designers and city planners must have at their disposal simple and effective tools for evaluating the economic feasibility of these two choices. This paper proposes a simple method to assess the economic effectiveness of green or cool roofs. It relies on the appraisal of the number of hours during which a building requires a cooling mechanical support for maintaining the indoor comfort conditions. This duty period of the cooling system is then simply converted into the cost of the needed electric energy.

Urban heat island (UHI) phenomenon, nowadays accentuated by global warming, is growing its negative influence on urban resilience, building energy budget and human comfort during summer. To reduce UHI effect, mitigation strategies are normally focused on actions related to urban design like the use of high reflectivity surfaces and increase of vegetation. But, as concerns building anthropogenic heat, the benefits of a possible reduction of the heat released by air conditioning systems to neighborhoods are often underestimate. An effective solution consists in transporting the heat emitted by chiller condensers elsewhere by using water as heat transfer fluid. The systematic use of seawater to cool chillers in an urban area of a coastal city was investigated. The modification of the UHI phenomenon was studied as well as the consequences on building cooling demands and chiller performances assessed in dynamic conditions. Urban weather files in presence of different types of chillers were elaborated by Urban Weather Generator model. Building cooling demands in the area were evaluated by using archetype modeling approach and EnergyPlus model. The algorithm adopted to assess chiller performances takes into account also the effect of part load working condition. The comparison of seawater cooled chillers technology versus the more diffuse use of air cooled chillers highlights a significant UHI effect reduction which reaches 57% during the night. As regards cooling demand increment caused by UHI, with seawater cooled chillers it is reduced of 58%. In the end, thanks to lower demand and higher chiller efficiency, seawater cooling chillers achieve an energy saving of 23.5%. Therefore this solution can foster the urban resilience and sustainability with an increasing contribution in front of the future climate scenario. Therefore, the introduction of a district cooling network is an important UHI mitigation strategy and its feasibility would have to be always verified between the possible actions.

Future energy scenarios focus on electricity as the main energy vector, because of its easier management and flexibility, in conjunction with the reduced use of carbon fuels. In such a context, also Sustainable Energy and Climate Action Plans (SECAPs) are promoting electricity-based technologies also in services usually relying on fossil fuels, such as ambient heating and domestic hot water preparation (DHW), by means of heat pumps. Moreover, heat pumps both fit perfectly with the Zero Energy Building (ZEB) perspective and offer major opportunities in a regional and urban perspective, since they offer many ways to optimize the exploitation of renewable energy sources (RESs). This paper shows quantitative analyses on possible applications of heat pumps in combination with the most typical RES in urban contexts, i.e. solar photovoltaics (PV).

The increased generation of electricity from renewable energy sources may imply issues in the management of national electric systems, due to the low predictability of electricity generation from renewable energy sources. In this regard, interesting opportunities come from the use of advanced control strategies for the management of electric devices such as heat pumps, able to exploit dynamic electricity prices aimed to induce users to absorb/generate electricity according with the electricity grid imbalance. In this paper, the results of building energy simulations applying tailored heat pump control strategies suitable for the integration within smart grids are presented. In particular, three heat pump control strategies are applied, whose action is based on the cost of electricity (absolute and relative to the following 12 h) and on the level of the local electricity generation from photovoltaics. The analyzed control strategies ensure relevant money savings (up to 30%) and increase the degree of energy self-consumption (up to 12% for exported electricity and 22% for imported electricity). The analysis considers also comfort issues and shows that the best results may be achieved commanding the heat pump basing on the generation of the photovoltaic system as well as on the simultaneous heating/cooling loads and electricity prices.

Tables of performance of installed HVAC (Heating, Ventilation and Air Conditioning) devices are important in the development of consistent building energy audits and appropriate control strategies. However, given the possible complexity of HVAC devices and the need for the deployment to computational environments, tables of performance should be passed in a more complete and flexible format, compared with the current practices in the HVAC sector. In such a context, this paper describes the phases of development and application of Artificial Neural Networks (ANNs) aimed at the assessment of the performance of a Dedicated Outdoor Air System (DOAS). ANNs are well renowned because of their applications in many important fields such as autonomous driving systems, speech recognition, etc. However, they may be used also to calculate the output of complex phenomena (like the ones involved in HVAC components) and are characterized by a very flexible and comprehensive formulation which would be able to adapt to any HVAC component or system. In the frame of this study, three ANNs have been developed and tested, for the full description of the performance of a DOAS. The developed ANNs were trained by means of data coming from a proprietary software. The achieved ANNs showed robust and reliable behavior and ensure high accuracy (mean absolute errors usually below 0.1 K on temperatures and 0.3% on capacity and power) and flexibility. Moreover, in some cases, they may be used also for the identification of anomalous data present among the sets of training and validation data.

CO2 based ventilation control is an eligible technology to reduce energy consumptions concerning ventilation air treatment and its distribution in particular in presence of highly variable occupancy. An experimental assessment of the performances of this control strategy is illustrated in this paper. The study refers to a historic building in Venice recently refurbished and subject to a preservation order. It concerns a demand controlled ventilation (DCV) system installed in a part of the building transformed in a university library and based on the use of CO2 sensors. A building management system (BMS) able to measure and record the required data was used as a tool for long term monitoring of the HVAC system. A comparison with alternative solutions was also carried on. The results permit to quantify remarkable energy savings, particularly strategic in the energy retrofit of historic buildings especially in presence of preservation orders. But the investigation highlights also the peculiarities of CO2 based ventilation control in meeting the indoor comfort requirement which suggest a systematic use of long term assessment to verify control efficacy in different operating conditions.

The interest of the building energy sector is leaning towards the measurement of building actual performance, as regards both indoor environment quality and energy consumption. Sensors and central elaboration units aimed at monitoring indoor environment and HVAC system parameters can also provide the basic infrastructure for further applications such as predictive and neuro-fuzzy controls. However, the cost of such systems is high, so they are mainly used in large buildings. This paper describes the main features and expected applications for a low-budget monitoring platform currently under development and tuning. In particular, the monitoring system was developed based on electronic prototyping platform Arduino and on sensors and devices usually available in the retail market of electronics. The monitoring platform has been designed with the following characteristics in mind: replicability, full remote control, portability, versatility, reliability and affordability.

The Zero Energy Building (ZEB) target and the higher affordability of photovoltaic (PV) systems are pushing Governments and large Companies operating in electricity generation and distribution network management to develop tools able to better define the potential productivity of PV systems on a large scale, such as solar maps. However, solar maps mainly consider phenomena related to weather and geometry, with a low level of detail on second order effects. This research aims at the integration of additional technical aspects into solar maps, by means of diagrams able to increase the reliability in the assessment of potential electricity generation. For this purpose, more technical factors are taken into account, such as the variation of PV panel efficiency with cell temperature, the shadow cast by the preceding PV panel array, here including the action of by-pass diodes, and the ratio of active area over the area available for installation.

This paper considers the topic of natural ventilation in school buildings that is faced not only for energy saving, but also for the fundamental exigency of the indoor comfort. This analysis is developed by measuring the concentration of carbon dioxide as a significant indicator of IAQ when pollution is mainly due to the presence of people. In this paper are presented the results of a monitoring campaign of the CO 2 levels carried on in classrooms. The measures show the criticality of IAQ with values often much higher than the limits specified by standard, but also the possibility to act effectively with the manual ventilation without excesses that could create comfort problems or waste of energy.

The spread of diffuse energy generation systems such as photovoltaics and combined heat and power generators will convert buildings from sole energy consumers into energy prosumers, i.e. energy producers and consumers. This will involve a much more dynamical interaction between buildings and the energy grid. As a consequence, electric distribution networks will be required to coordinate the energy draw/supply in order to optimize the use of renewable energy sources and preserve the reliability of the energy dispatch system, thus becoming smart grids. Smart grids will be able to act as coordinators of energy flows between diffuse energy producers and consumers, but buildings will be mainly managed in order to minimize their interaction with energy grids, thus minimizing the volatility of energy supply/draw, thus they will integrate energy management systems aimed at taking advantage of locally generated energy. In fact, buildings will be required to locally generate as much energy as possible, towards a Zero Energy Building perspective. For this purpose they will exploit technologies able to modulate energy demand and production by a suitable design of the building. So how will buildings, and consequently the related architecture, evolve in order to achieve these goals? In this paper the present status of the art as well as building configurations, procedures and energy management strategies able to ensure the best integration of typical residential and office buildings into smart grids are analysed.

Ground source heat pump (GSHP) systems are spreading also in Southern Europe, due to their high energy efficiency both in heating and in cooling mode. Moreover, they are particularly suitable in historical cities because of difficulties in the integration of heating/cooling systems into buildings subjected to historical preservation regulations. In these cases, GSHP systems, especially the ones provided with borehole heat exchangers, are a suitable solution instead of gas boilers, air-cooled chillers or cooling towers. In humid soils, GSHP systems are even more interesting because of their enhanced performance due to higher values of soil thermal conductivity and capacity. In this paper, GSHP systems operating under these boundary conditions are analyzed through a specific case study set in Venice and related to the restoration of an historical building. With this analysis the relevant influences of soil thermal conductivity and yearly balanced heat transfer in the design of the borehole field are shown. In particular, the paper shows the possibility to achieve higher compactness of the borehole field footprint area when yearly balanced heat transfer in the borehole field is expected. Then, the second set of results contained in the paper shows how GSHP systems designed for high humidity soils and yearly balanced heat loads at the ground side, even if characterized by a compact footprint area, may still ensure better performance than other available and more common technologies such as boilers, air-cooled chillers, chillers coupled with cooling towers and heat pumps and chillers coupled with lagoon water. As a consequence, in this last comparison, the efficiency of GSHP systems is confirmed even when compact borehole installation areas are used. The analysis is performed in terms of both input energy consumption ratio and primary energy ratio and takes into account the energy consumption of auxiliary devices as well. The conclusions are drawn in terms of percentage, thus allowing the reader to extend the results achieved in this paper to systems operating in other contexts under similar boundary conditions.

The EPBD (Energy Performances of Buildings Directive) updated on 9 July 2010 imposes new rules for energy savings in buildings. By 31 December 2020 all new buildings must be nearly Zero Energy Buildings (nZEB) with reference to the consumption of fossil fuels. The roadmap that each nation is adopting for this purpose imposes a further significant increase in the share of the building energy requirement covered by renewable energy. Achieving this goal at acceptable costs for the communities represents a real challenge considering the current state of the art. The role of Eco-Architecture will be fundamental in this phase of introduction and spread of innovative techniques in the design of building-plant system. For this aim, the installation of heat pumps for building heating is able to contribute significantly in terms of better energy performance and exploitation of renewable energy. In fact, in the EPBD the energy from heat sources of heat pumps (air, ground, water) is considered renewable energy. An assessment about the possibilities and limits of the electric heat pump installation in dwellings is here reported for different case studies and climates in Europe.