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In Italy, the recast of the European Directive on Energy Performance of Buildings (2010/31/EU) is implemented with specific definitions and deadlines for Nearly Zero Energy Buildings. We focus our attention on schools, not only for their social importance and high visibility, but also because in the next future a significant share of these buildings is likely to undergo refurbishment for different purposes than the energetic one. We start to analyze the criticalities associated with the current Italian legislation on NZEBs by means of a bottom-up approach: we choose a benchmark secondary school (located in Pisa, hosting about 750 students) and perform an accurate energy audit of the building system, together with an energy and economic simulation of an NZEB retrofit. More in detail, we present the case study and explain its choice as an appropriate representative of the existing scholastic buildings in Centre Italy; besides, we build two concurrent energy models, based on tailored and asset rating methods, we propose technically-feasible actions for deep renovation, and simulate, for both models, the associated energy and economic savings after 20 years of use. We observe long payback periods of the retrofit measures, due to low yearly energy uses in the existing configuration. Based on these results, we attempt to extend to a more general level the considerations on strengths and weaknesses encountered in the present application of the Italian regulation on NZEBs. [ABSTRACT FROM AUTHOR]

In Italy, the recast of the European Directive on Energy Performance of Buildings (2010/31/EU) is implemented with specific definitions and deadlines for Nearly Zero Energy Buildings. We focus our attention on schools, not only for their social importance and high visibility, but also because in the next future a significant share of these buildings is likely to undergo refurbishment for different purposes than the energetic one. We start to analyze the criticalities associated with the current Italian legislation on NZEBs by means of a bottom-up approach: we choose a benchmark secondary school (located in Pisa, hosting about 750 students) and perform an accurate energy audit of the building system, together with an energy and economic simulation of an NZEB retrofit. More in detail, we present the case study and explain its choice as an appropriate representative of the existing scholastic buildings in Centre Italy; besides, we build two concurrent energy models, based on tailored and asset rating methods, we propose technically-feasible actions for deep renovation, and simulate, for both models, the associated energy and economic savings after 20 years of use. We observe long payback periods of the retrofit measures, due to low yearly energy uses in the existing configuration. Based on these results, we attempt to extend to a more general level the considerations on strengths and weaknesses encountered in the present application of the Italian regulation on NZEBs. [ABSTRACT FROM AUTHOR]

The design of HVAC systems for museum exhibition rooms is a challenging issue, as artworks require specific hygrothermal conditions to prevent deterioration: on one hand, technical equipment should be able to maintain optimal microclimate, even in critical conditions (e.g., high visitors' presence); on the other hand, energy inefficiency due to oversized system should be avoided. Specifications and guidelines provide hygrothermal values for several typologies of artworks, but the suitability of these values has not been checked through risk assessment methods. In this work, risk assessment models are used to verify the suitability of hygrothermal values suggested by in-force specifications for three artifacts typologies, i.e. paper, panel paintings and wooden sculptures. Results show that current values are suboptimal for two artwork types. Consequently, a procedure for the artwork risk minimization is applied to identify new suitable hygrothermal values for panel paintings and wooden sculptures. The application of these risk assessment methods is also useful in the characterization of actual microclimate in museum exhibition rooms, through the analysis of monitored data. Moreover, risk assessment methods can be used together with suitability indexes of microclimate performance to assess actual microclimate suitability or evaluate risks in indoor environment dynamic simulations. This procedure can be useful for the decision-making community to provide artwork-depending optimal hygrothermal values for museum environments to professionals. Furthermore, it can also be applied by technicians to obtain reference values to minimize risks and, if possible, achieve additional objectives (e.g., energy savings, human thermal comfort). [ABSTRACT FROM AUTHOR]

This paper deals with the cost-optimal sizing of solar technologies for thermal and electrical needs of residential or tertiary nearly Zero-Energy buildings. The proposed design procedure is based on lifetime simulation of building loads and energy systems; therefore, according to proper cost-optimality considerations, it is possible to find the best sizing of both heat and electricity generators in the context of high-efficiency buildings (e.g. number of solar thermal and PV modules). The paper is divided in two parts. In this first part, we describe general features and principles of the methodology, together with the physical models of building-plant system. Building requirements of thermal and electrical energy are evaluated according to internal loads and external climate, while energy system operation is simulated by a full set of equations reproducing the coupled behavior of each piece of equipment. A preliminary application example referring to a nearly Zero-Energy Building is also illustrated: In the second part of the work, we will apply and discuss the overall simulation-based optimization procedure. Results show the notable benefits of the proposed design approach with respect to traditional ones, in terms of both energy and economic savings. Besides, the proposed methodology can be successfully applied in the more general framework of Net Zero Energy Buildings (NZEBs) in order to fulfill recent regulatory restrictions and objectives in building energy performances. [ABSTRACT FROM AUTHOR]

In this paper, the second of two parts, we apply the cost-optimal design method illustrated in Part 1 [1] to a case study. We select a farm hostel located in Enna, Italy, as the local climate and the required energy services are suitable for the development of a solar-assisted nearly zero-energy building. The system is connected to the electric grid and does not use any other thermal energy vector. Energy demand includes heating, cooling, domestic hot water production, lighting and other electric uses, viz. inductance cooking, food refrigeration, local dehumidification, household appliances, and office devices. The building-plant system is described in terms of both technical characteristics of each component and internal loads. According to the proposed simulation-based methodology, we investigate the best design configuration by minimizing the lifecycle cost after 20 years of operation. The results of the procedure identify the optimal solution, in terms of number of solar thermal and photovoltaic panels, volume and control strategy of the thermal storage. Other outputs are the dynamic and seasonal energy balance of each system component and of the whole system, and additional economic parameters. The results show that the proposed method leads to a very favorable design with relevant notable economic and energy benefits with respect to a no-solar design solution ( ΔC TOT =11%, ΔE IN TOT =67%). However, several nearly optimal configurations provide very similar outcomes in terms of lifecycle costs, with different initial investment and energy performances. Consequentially, we introduce a multi-objective optimization approach aimed at identifying the best solution in terms of investment availability and energy objectives. [ABSTRACT FROM AUTHOR]

SEAS is an energy auditing software that can simulate residential, office, school, and hospital buildings, providing energy requirements for heating, domestic hot water production, ventilation, lighting, and other electrical uses. In order to validate this quasi-steady-state tool, we simulated in SEAS several reference cases (based on EN 15265 benchmark room) and a residential dwelling. We also used the dynamic simulation software TRNSYS and compared the results of the two software in terms of seasonal energy requirements for space heating and energy fluxes through the elements of the building envelope. Most of SEAS results are in good agreement with EN 15265 and with TRNSYS. Nonetheless, we pointed out that SEAS lacks in accuracy when it simulates high thermal inertia buildings with intermittent heating: for these particular cases, new correlations for dynamic parameters and reduction factors should be developed. [ABSTRACT FROM AUTHOR]

Radiant heating coupled to a heat pump is a particularly energy-efficient system, recommended in new constructions. However, the potential energy savings associated with this high thermal inertia system can only be achieved with appropriate control laws, to be tested in a full building–plant simulation environment. The developed transient code concurrently solves three tailored dynamic models of each involved sub-system, namely: building envelope (a benchmark room defined by ISO 13791), radiant floor (designed in accordance with EN 1264-2), and heat pump (an air-to-water electrically-driven modulating unit). Different control strategies were implemented, such as variation of internal temperature set-point dead band, supply temperature to radiant panels, and heating modes. Among the examined variables, we found that the higher energy savings (up to 15%) can be obtained by a proper choice of the supply temperature: in particular, fixed supply temperature should be preferred to climate-based control for this case study. The developed model can be used for optimal design of new systems and associated controls and for accurate energy audits of existing buildings employing these technological solutions. [ABSTRACT FROM AUTHOR]

The paper deals with the multi-objective optimization of the HVAC control in museums. Scientific literature, technical standards and museums stakeholders mainly focus on the single-objective of artefacts conservation. However, a major attention should be paid at visitors' comfort and energy consumption, without compromizing artwork integrity. In this work, we propose and apply a methodology to find the best control of the air-handling unit to concurrently optimize the three objectives. The proposed methodology is based on the achievement function method and finds the Pareto-optimal value of the HVAC control variables over the operational period. The priority given to each objective can be customized by changing the reference point of the achievement function. The method is applied to a museum in Italy hosting paper artworks during summer. Both exhibition room and HVAC system are simulated through an in-house dynamic model. The results show that all three objectives are improved with respect to typical fixed setpoint values (i.e., T = 23 °C and RH = 50%). Depending on the reference point, different profiles of indoor hygrothermal parameters are found; in any case, improvements of each of the objective functions indexes (equivalent lifetime multiplier for artwork preservation, predicted percentage of dissatisfied, and energy consumption) are obtained with respect to fixed setpoint strategy. The multi-objective optimization of museums with paper artworks in summer periods encourages low indoor temperatures. This would lead to slightly increased energy consumptions, which can be limited, by reducing the ventilation rate to 3–3.5 1/h instead of the typical 4–5 1/h. • The multi-objective methodology optimizes museums HVAC control in each timestep. • Objective functions are artwork preservation, visitors' comfort, and energy saving. • Objectives priority is chosen by changing the optimization reference point. • All objectives are concurrently improved with respect to fixed-setpoint strategies. • A case study compares different control strategies and objectives priorities. [ABSTRACT FROM AUTHOR]

• The TES allows a cost and primary energy consumption up to 8% and 13% respectively. • The energy flexibility depends on the TES capacity and the operation control. • The DR specific cost is reduced between 45% and 75% with TES installed. • Performance maps can be created to characterise building flexibility potential. The present paper assesses the capability of a cost-optimal control strategy to activate demand response actions in a building equipped with an air-source heat pump coupled with a water thermal storage system. Commencing with a reference scenario where no demand response actions are considered, the electricity consumption pattern and the operational cost are evaluated. Several demand response scenarios are next considered by adapting consumption patterns by reduction of baseline heat pump power consumption. The difference between the operational cost evaluated under a specific demand response program and the benchmark cost are used to assess the marginal cost that should be considered to provide incentives to promote user participation in demand response programs. The results illustrate the effectiveness of thermal energy storage for reducing the total system operational cost and its seasonal primary energy consumption, both with and without demand response actions. The application of the proposed methodology over the whole heating season, allows performance maps to be created that can be used either by the grid-operator or end-user to identify the best demand response action to be implemented on any particular day. These maps represent useful decision tools to assess and optimise the flexibility potential while meeting end-user needs. [ABSTRACT FROM AUTHOR]