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Scalable dynamic simulation-based methodology for the energy retrofit of existing buildings
Full text linkIt is widely recognized that the building sector largely contributes to the total European energy consumption with a 40% influence on the total assessed energy uses. To this regard the EPBD recast Directive promotes nearly zero energy buildings (nZEB) for the public and the private sector as a mandatory requirement by 2020. Given the low energy efficiency of old buildings, concerns about the state of the existing building stock should be seriously considered as most of the energy consumption is attributable to the existing buildings. Additionally, residential buildings are often seen as long-term assets, setting thus a low replacement rate, approximately 1% per year in Europe, of old buildings by new ones. To this regard, larger energy savings can be achieved with the energy retrofitting of the existing building stock, rather than with the construction of relatively small proportion of new high performing buildings. Therefore, the refurbishment of the existing building stock has to be primarily planned and accomplished in order to achieve a timely reduction on the buildings energy consumption. Concerning this, the EPBD recast, as policy driver for reducing European energy use in buildings, has been representing the first and main legislative reference. According to it Member States must ensure that minimum energy performance requirements are set with a view of achieving at least cost-optimal levels for buildings, building units and building elements" by means of a comparative methodology framework applied to new constructions and existing buildings undergoing major renovations. The methodology specifies how to compare energy efficiency measures in relation to their energy performance and to the cost attributed to their implementation, and how to apply these to selected reference buildings with the aim of identifying cost-optimal levels of minimum energy performance requirements. A cost optimal level is defined as the energy performance level, which leads to the lowest cost during the estimated economic lifecycle of the building. A measure is considered cost-effective when the cost of implementation is lower than the achievable benefits, during the expected life of the measure. This type of analysis allows defining energy renovation scenario based on their energy and economic optimum. Within the complex scenario described above, this Ph.D. thesis aims to provide a scalable methodology for the definition of energy retrofit scenarios to be applied to existing buildings, based on the use of dynamic building simulation models. The methodology targets the existing building stock given the large energy savings that can be achieved from existing buildings. It builds on an energy and economic assessment of energy efficiency measures applied to different building typologies. The energy and economic assessment are respectively carried out by means of dynamic building simulation and a cost-optimality approach. The cost optimal analysis was chosen for the aim of this study for its systematic approach in defining energy retrofit interventions based on their energy and economic optimum. The term "scalable" is used for defining the methodology as the studied energy retrofit scenarios can vary depending on the "scale" of the study. Two main scales of buildings can be distinguished: building stock or single buildings. When retrofit interventions are studied to be applied to wide portion of the building stock, as for example at national level, representative building models are used. They correspond to reference buildings representative of a certain building typology, construction age and geographic location. Within this thesis, a methodology for their definition was defined and various reference buildings for the Italian context were created. On the contrary, when it is necessary to study specific and customized retrofit measures, a single existing building is modelled. In this case, compared to the case of the reference buildings, larger quantity of data and a higher degree of detail are necessary. These building models are customized based on the existing buildings characterization (e.g. building envelope, system, etc) and when applicable, based also on data from monitoring. To this regards, when detailed information about the building real operation from monitoring is available, the building model need to be calibrated based on measured data. For a model to be calibrated, the building energy consumption predicted by the simulation program, has to match the consumption measured from monitoring. Calibrated models can be used for comparing the baseline situation of the building (calibrated and not retrofitted) with other simulation results relative to the application of building renovation interventions. To this regard, within this Ph.D. thesis, a literature review on the most common calibration techniques currently in use for the calibration of building models was conducted. Additionally two case studies were calibrated by means of two different approaches: a trial and error approach and an optimization-based calibration. For both scale of buildings (building stock and single buildings), dynamic building simulation was employed for the energy assessment. Building simulation application has expanded since mid-‘70s building simulation as an attempt to emulate reality. To date, it is much more common to employ building simulation in post construction or advanced building design phases rather than in early phases. In particular building simulation is frequently used for the prediction of energy savings by assessing energy retrofit interventions on existing buildings. To this regard, given its wide application and the high level of detail of the analysis performed (dynamic analysis), building simulation was chosen within this thesis, as a tool for the energy assessment of buildings and of the relative energy renovation interventions. Finally, the economic assessment of the energy retrofit measures was carried out by means of the cost optimal methodology, as defined by the EPBD recast. The methodology allowed defining energy renovation interventions based on their economical and energy optimum. The Directive requires to define different packages of energy efficiency measures, which can be applied to reference representative buildings but also to single and existing building for energy and economical assessments. The energy assessment of a building can be carried out with analytical or simplified methods, but dynamic building simulation is strongly suggested, as performed within this thesis. For the economic assessment, the global cost method was employed based on the calculation method of the Standard EN 15459 as advised by the EBPD. The global cost method considers, for each energy efficiency measure, the initial investment, the sum of the annual costs for every year (including energy costs) and the final value, all with reference to the starting year of the calculation period. In order to define different energy retrofit solution and set the minimum energy performance requirements, within the Ph.D. thesis, the cost optimal approach was applied to both the considered scale of buildings: to the building stock scale with three reference buildings, and to the single buildings scale with two calibrated buildings. A set of energy efficiency measures was defined and applied to the case studies for evaluating the financial and energy performance gap between the cost-optimal solutions and nZEB levels, respectively. For the building stock, different energy retrofit solutions are defined as final outcomes. Given the use of representative models (reference buildings), the retrofit solutions can be replicated to several buildings, among the same building typology. In this sense, different energy retrofit solutions can be established. On the other hand, for single buildings, the energy retrofit solution studied is specific and customized barely to the analyzed case stud
La calibrazione dei modelli di simulazione energetica. Metodologie ed applicazione ad un caso studio
No full textIn questo articolo vengono introdotte le metodologie di calibrazione dei modelli termoenergetici degli edifici, da quelli semplificati a quelli maggiormente dettagliati. Gli aspetti da considerare per effettuare la calibrazione di un modello riguardano l’identificazione dei parametri di input che maggiormente influenzano l’output del modello, i criteri da valutare e i parametri di soglia per poter considerare calibrato un modello. Infine la calibrazione di un caso studio è descritta insieme all’approccio metodologico adottato
Methodologies and advancements in the calibration of building energy models
Full text linkBuildings do not usually perform during operation as well as predicted during the design stage. Disagreement between simulated and metered energy consumption represents a common issue in building simulation. For this reason, the calibration of building simulation models is of growing interest. Sensitivity and uncertainty analyses play an important role in building model accuracy. They can be used to identify the building model parameters most influent on the energy consumption. Given this, these analyses should be integrated within calibration methodologies and applications for tuning the parameters. This paper aims at providing a picture of the state of the art of calibration methodologies in the domain of building energy performance assessment. First, the most common methodologies for calibration are presented, emphasizing criticalities and gaps that can be faced. In particular the main issues to be addressed, when carrying out calibrated simulation, are discussed. The standard statistical criteria for considering the building models calibrated and for evaluating their goodness-of-fit are also presented. Second, the commonly used techniques for investigating uncertainties in building models are reviewed. Third, a review of the latest main studies in the calibrated simulation domain is presented. Criticalities and recommendations for new studies are finally provide
Livelli di prestazione energetica ottimali per edifici a energia quasi zero: il caso di un edificio multifamiliare
No full textIl livello di prestazione energetica ottimale in funzione dei costi (cost optimal level of energy performance) è la quantità di energia necessaria per il soddisfacimento del fabbisogno energetico dell'edificio, che richiede il costo più basso durante il ciclo di vita economico stimato dell'edificio stesso. Il concetto è stato definito dalla Direttiva Europea 2010/31/UE del 19 maggio 2010 (EPBD recast) che richiede agli Stati Membri l'applicazione di un quadro comparativo metodologico per il calcolo del livello ottimale di prestazione energetica su edifici di riferimento. Tale quadro metodologico prevede lo sviluppo, da parte di ciascuno Stato Membro, di una serie di edifici di riferimento a livello nazionale o regionale (Reference Building), da utilizzare come edifici tipo rappresentativi del patrimonio edilizio, ed ai quali applicare ipotesi di misure per il miglioramento dell'efficienza energetica per determinare i target prestazionali degli edifici ad energia quasi zero. L'obiettivo di questa ricerca è l'individuazione per un edificio residenziale esistente del livello di prestazione energetica ottimale in funzione dei costi, attraverso l'applicazione del quadro metodologico comparativo della Direttiva europea EPBD recast. L'edificio di riferimento è un edificio multifamiliare per appartamenti realmente esistente (Real Building), costruito negli anni ‘60 e selezionato dal database di archetipi del progetto europeo IEE TABULA. All'edificio sono state applicate differenti misure di efficientamento energetico, valutate a livello energetico attraverso l'uso di un software di simulazione dinamica (EnergyPlus) ed a livello economico attraverso l'applicazione del metodo del costo globale secondo la norma UNI EN 1545
Italian benchmark building models: the office building
No full textThis article describes the development of Italian
reference building models, as valuable decisional
tools to to be used from the very start of the design
process. As a first step, a contextualization of the
benchmark building model for the large office
building created by the US DOE (Department of
Energy) was made. A method suitable for different
building typology was identified. This work was
limited to the large office case study across seven
location in the North of Italy. Afterwards a benchmark
model for the large office building, based on various
research over Italian Office building stock was defined
Impact of low investment strategies for space heating control: Application of thermostatic radiators valves to an old residential building
Full text linkWith an old mean construction age, Italian buildings are considered as long-lasting goods; 75% and 17% of Italian live respectively in buildings built before 1990 and before 1950. The potential energy savings that can be achieved from the refurbishment of existing dwellings are clearly high. To this regard, the European Directive EPBD recast defines a comparative framework to improve buildings energy performance aiming to the nearly zero energy target by 2020. It is thus important to point out energy retrofit actions to be widely applied to the whole existing buildings stock and to be cost optimal. This paper analyzes the application of space heating control devices such as thermostatic radiators valves (TRVs) on an old existing multi-family building in Turin by means of the EnergyPlus dynamic simulation code. Measured data of the energy supplied by the district heating network were used for calibrating the model. In order to evaluate the impact of the TRVs, simulations were performed with and without TRVs. The application of the dynamic energy simulation to different patterns of TRVs use was proved to bring back significant energy savings from a minimum of 2% up to a maximum of 10
Cost optimality assessment of a single family house: Building and technical systems solutions for the nZEB target.
No full textEurope has set a clear path to guide Member States into the accomplishment of the nearly zero energy buildings (nZEBs) target. To this regard, within EPBD recast directive, a cost optimality procedure has been defined. This study presents different cost optimal solutions of building and technical systems for nZEBs in Italy. In total 40 economically and technically feasible energy efficiency measures for a high performing single family house were analyzed. Special attention was devoted to the study of the building technical systems. Achieving a net zero balance required a high efficient system combined with high insulation and a large PV system, which plays a key role in the nearly and net zero building energy balance. Three net zero energy balance solutions, based on all electric systems, were presented. Net ZEB solutions allowed also the building carbon footprint to be reduced by 40% compared to the reference case study. Without proper financial subsides, net ZEB solutions are still far for being economic feasible, having a global cost 212-313 €/m2 higher than cost optimal solutions. In conclusion, this paper aims to present guidelines for designing reference building envelope and technical systems solution for residential nZEB
Livelli di prestazione energetica ottimali per edifici a energia quasi zero: creazione degli edifici di riferimento
No full textIl livello di prestazione energetica ottimale in funzione dei costi (cost optimal level of energy performance) è la quantità di energia necessaria per il soddisfacimento del fabbisogno energetico dell'edificio che richiede il costo più basso durante il ciclo di vita economico stimato dell'edificio stesso. Il concetto è stato definito dalla Direttiva europea 2010/31/UE del 19 maggio 2010 (EPBD recast) che richiede agli Stati Membri l'applicazione di un quadro comparativo metodologico per il calcolo del livello ottimale di prestazione energetica su edifici di riferimento. Tali edifici di riferimento, denominati reference buildings a livello europeo, sono edifici rappresentativi del patrimonio edilizio esistente e di nuova costruzione in termini di caratteristiche tipologiche, costruttive, geografiche e climatiche. In particolare è richiesto a ciascuno Stato Membro lo sviluppo, a livello nazionale o regionale, di almeno un reference building per edifici di nuova costruzione e due per edifici esistenti sottoposti a ristrutturazione, in funzione alla destinazione d'uso. La creazione di modelli di edifici di riferimento è un'operazione complessa e di difficile risoluzione, che dipende dall'origine e dalla tipologia di dati utilizzati per loro determinazione. In particolare, è possibile procedere sulla base di fonti statistiche di dati (Theoretical Building), di scelte basate sull'esperienza (Example Building), oppure individuare un edificio reale esistente come edificio rappresentativo (Real Building) di una specifica categoria edilizia e di un'epoca di costruzione. Lo scopo di questa memoria è approfondire il concetto di reference building, così come è attualmente trattato a livello internazionale e fornire le basi teoriche, dal punto di vista metodologico, per la definizione di tali edific
Optmization-based calibration for dynamic building simulation models: A case study
No full textThis study presents an original methodology for calibrating building energy models based on monitored data. An optimization-based approach was applied to a monitored test building coupling the building simulation program EnergyPlus with the optimization software GenOpt. An objective function was set to minimize the difference between the simulated and the monitored energy consumption at the hour time scale, varying the building model parameters selected at the beginning as the most influencing. After calibration, the observed heating energy consumption of the case study matched closely the monitored data, the model accuracy was verified according to the MBE and the Cv(RMSE) limit set by the ASHRAE guideline 1
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