Consumers' Willingness Towards Net Zero Energy Settlements and Influence of Occupant Behaviour on Building Energy Efficiency and Indoor Comfort in a Real Case Study in Italy

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(1)UNIVERSITÀ DI PISA SCUOLA DI INGEGNERIA. Corso di Laurea Magistrale in Ingegneria Edile e delle Costruzioni Civili TESI DI LAUREA. CONSUMERS’ WILLINGNESS TOWARDS NET ZERO ENERGY SETTLEMENTS AND INFLUENCE OF OCCUPANT BEHAVIOUR ON BUILDING ENERGY EFFICIENCY AND INDOOR COMFORT IN A REAL CASE STUDY IN ITALY. RELATORI. CANDIDATO. Ing. Giacomo Salvadori (UNIPI) Prof. Ing. Fabio Fantozzi (UNIPI) Ing. Anna Laura Pisello (UNIPG) Ing. Cristina Piselli (UNIPG). Anno Accademico 2017/2018. Lorenzo Diciotti.

(2) Title Sheet TITLE. Consumers’ Willingness Towards Net Zero Energy Settlements and Influence of Occupant Behaviour on Building Energy Efficiency and Indoor Comfort in a Real Case Study in Italy La Propensione dei Consumatori Verso Quartieri ad Energia Netta Zero e l’Influenza del Comportamento degli Occupanti sull’Efficienza Energetica e il Comfort all’Interno dell’Edificio in un Caso di Studio Reale in Italia. KEYWORDS. net zero energy settlements, nearly zero energy building, sustainable energy technologies, real life case study, environmental performance, pre-occupancy checks, energy model calibration, dynamic energy simulation, occupant behavior, occupancy profiles, electricity consumption, consumers’ willingness, technology acceptance model, subjective knowledge, environmental concern, perceived usefulness, sustainable consumerism. quartieri a energia netta zero, edifici a energia quasi zero, tecnologie energetiche sostenibili, caso studio reale, prestazioni ambientali, verifiche pre-occupazione, calibrazione dei modelli di simulazione energetica, simulazione energetica dinamica, comportamento degli occupanti, profili di occupazione, consumo di elettricità, propensione dei consumatori, modello di accettazione della tecnologia, conoscenza soggettiva, preoccupazione ambientale, utilità percepita, consumismo sostenibile.. AUTHOR. Lorenzo Diciotti. STUDENT N°. 457871. PROJECT TYPE. Post graduate Master's Degree. UNIVERSITY. Università di Pisa – Scuola di Ingegneria DESTEC (Energy Department). HOST UNIVERSITY. Università degli Studi di Perugia CIRIAF - Centro Interuniversitario di Ricerca sull'Inquinamento e sull'Ambiente Mauro Felli. SUPERVISORS. Ing. Giacomo Salvadori (UNIPI) Prof. Ing. Fabio Fantozzi (UNIPI). Ing. Anna Laura Pisello (UNIPG) Ing. Cristina Piselli (UNIPG).

(3) A tutti coloro che hanno sempre creduto in me, sostenendomi fino alla fine.. A Harry & Emy, fedeli amici, resterete sempre nel mio cuore..

(4) Acknowledgments This thesis represented an important opportunity for me to grow both professionally and personally. I am grateful to Professor Fabio Fantozzi for giving me the opportunity to collaborate with the University of Perugia to develop a current and innovative topic. I would like to thank Ing. Giacomo Salvadori, for his assistance and for his always precise advice. I would particularly like to thank Ing. Anna Laura Pisello and Ing. Cristina Piselli for the hospitality reserved for me at the Interuniversity Research Center - CIRIAF of Perugia, for the attention dedicated to my thesis and for the interesting work developed together. I am particularly grateful to Claudia for being patient and kind and for always making me feel important. My sincere gratitude also goes to my colleagues, friends and anyone who has been close to me during this time. Finally, I want to give special thanks to all my wonderful family, for always encouraging me and for supporting me in all my efforts and always being close to me.. Ringraziamenti Questa tesi ha rappresentato per me un importante occasione di crescita sia sul piano professionale che su quello personale. Sono grato al Professor Fabio Fantozzi, per avermi dato l’opportunità di collaborare con l’Università degli Studi di Perugia per lo sviluppo di un tema attuale e innovativo. Vorrei ringraziare l’Ing. Giacomo Salvadori, per l’aiuto fornitomi e per i suoi consigli sempre precisi. Vorrei ringraziare in modo particolare l’Ing. Anna Laura Pisello e l’Ing. Cristina Piselli per l’ospitalità riservatami al Centro Interuniversitario di Ricerca - CIRIAF di Perugia, per l’attenzione dedicata alla mia tesi e per l'interessante lavoro sviluppato insieme. Sono particolarmente grato a Claudia per essere stata paziente e gentile e per avermi sempre fatto sentire importante. La mia sincera gratitudine va anche ai miei colleghi, amici e a chiunque mi sia stato vicino in questo periodo. Infine, voglio rivolgere un ringraziamento speciale a tutta la mia splendida famiglia, per incoraggiarmi sempre e per avermi sostenuto in tutti i miei sforzi..

(5) Contents Abstract.......................................................................................................... 1 Sintesi............................................................................................................. 2 Introduction ................................................................................................... 4 CHAPTER 1 - Towards Net Zero Energy Settlements....................................... 7 1.1 Energy Consumption in the European Built Environment .......................................... 7 1.1.1 Climate Change and Urbanization in Europe ....................................................... 8 1.1.2 The Urban Heat Island (UHI) Effect: Causes and Mitigation Strategies ............. 11 1.2 Net Zero Energy Buildings ......................................................................................... 18 1.2.1 Net Zero Energy Building: Definition and Classification ..................................... 24 1.3 Net Zero Energy Settlements .................................................................................... 32 1.4 Importance of Energy Prevision Accuracy for Zero-Energy Buildings ....................... 38 1.4.1 User-Building Interaction ................................................................................... 38 1.4.2 Surveys on NZEB Performance ........................................................................... 39. CHAPTER 2 - Horizon 2020 Zero-Plus Project................................................ 41 2.1 The Project ................................................................................................................. 41 2.2 Innovative Technologies Implemented at Settlement Level..................................... 44 2.2.1 Advanced Envelope Components by Fibran....................................................... 46 2.2.2 Building Integrated PV by SBskIn........................................................................ 47 2.2.3 FRESCO Solar LFC + TES tank by ARCA ................................................................ 48 2.2.4 FAE HCPV by ARCA.............................................................................................. 49 2.2.5 WindRail Solar and Wind Driven Energy System by ANERDGY .......................... 49 2.2.6 FREESCOO Air Conditioning System by Solarinvent ........................................... 51 2.2.7 REACT by ABB ..................................................................................................... 52 2.2.8 Integrated Energy Resources Management by ABB .......................................... 53 2.3 Case Studies ............................................................................................................... 54 2.3.1 Peyia Village, Paphos, Cyprus ............................................................................. 54 2.3.2 Voreppe, Grenoble, France ................................................................................ 55 2.3.3 Derwenthorpe Community, York, UK ................................................................. 56 2.3.4 Granarolo dell’Emilia, Bologna, Italy .................................................................. 57 i.

(6) 2.4 Italian case Study: Results already Achieved ............................................................ 62 2.4.1 Optimization of the Energy and Environmental Performance at Building Scale 63 2.4.2 Design and Optimization of the NZE Technologies to be Implemented at the Settlement Scale .......................................................................................................... 64. CHAPTER 3 - Ergonomics of the Thermal Environment ................................ 67 3.1 Human Body and Clothes .......................................................................................... 69 3.2 Indoor Microclimate: The Building Parameters ........................................................ 75 3.3 Comfort and Health in Indoor Environment: Indoor Air Quality .............................. 76 3.3.1 Human Pollution: Carbon Dioxide (CO2) ............................................................ 78 3.4 The Indices of Feeling-Predicted Mean Vote PMV and Percentage People Dissatisfied PPD................................................................................................................................... 79 3.4.1 Predicted Mean Vote (PMV)............................................................................... 82 3.4.2 Predicted Percentage of Dissatisfied Index (PPD) .............................................. 83 3.4.3 Definition of the Comfort Categories ................................................................. 84 3.5 Adaptive Thermal Comfort ........................................................................................ 85. CHAPTER 4 - Field Experiment – Pre-Occupancy Tests ................................. 89 4.1 M&V Process ............................................................................................................. 89 4.2 Pre-occupancy Tests in the Italian case Study of the Zero-Plus Project ................... 92 4.2.1 The Monitoring Setup......................................................................................... 92 4.2.2 Infrared Thermography ...................................................................................... 97. CHAPTER 5 - Model Calibration and Validation .......................................... 101 5.1 Introduction ............................................................................................................. 101 5.2 DesignBuilder Simulation Tool and Input Weather Data ........................................ 103 5.3 Italian Case Study: Final Design State...................................................................... 105 5.4 The Calibration Procedure ....................................................................................... 108 5.4.1 Model Calibration Criteria ................................................................................ 109 5.4.2 Building Model Input ........................................................................................ 110 5.5 Results of Model Calibration ................................................................................... 113. CHAPTER 6 - Impact of Occupant Behaviour on NZEB Performance ........... 115 6.1 Introduction ............................................................................................................. 115 6.2 Methodology ........................................................................................................... 119 6.2.1 Occupant Behavior Lifestyles ........................................................................... 119 ii.

(7) 6.2.2 Household Compositions.................................................................................. 119 6.2.3 Heating and Cooling System ............................................................................. 122 6.2.4 Equipment ........................................................................................................ 122 6.2.5 Lighting ............................................................................................................. 124 6.2.6 Influence of the Shading and Ventilation Strategy .......................................... 124 6.3 Results...................................................................................................................... 128 6.3.1 Effect of Occupant Behavior on Energy Performance...................................... 128 6.3.2 Effect on Thermal Comfort Conditions............................................................. 136 6.4 Discussion and Implication ...................................................................................... 140. CHAPTER 7 - Questionnaire Analysis: Consumers’ Willingness towards Net Zero Energy Settlements ............................................................................ 143 7.1 Introduction ............................................................................................................. 143 7.2 Technology Acceptance Model (TAM) and Hypothesis Development.................... 148 7.2.1 Theoretical Framework and Hypotheses ......................................................... 150 7.3 Reporting Structural Equation Modeling (SEM) and Confirmatory Factor Analysis (CFA): A Review.............................................................................................................. 158 7.3.1 CFA .................................................................................................................... 159 7.3.2 SEM ................................................................................................................... 162 7.4 Methodology ........................................................................................................... 170 7.4.1 Data collection and Measure design ................................................................ 170 7.4.2 Reliability and Validity of the Measurement Model ........................................ 174 7.4.3 Data analysis ..................................................................................................... 176 7.5 Results...................................................................................................................... 176 7.5.1 Descriptive Statistics......................................................................................... 176 7.5.2 Structural Model: Goodness of Fit Statistics, Modeling Comparison, and Hypothesis Testing..................................................................................................... 177 7.6 Discussion and Implications .................................................................................... 179. Conclusions and Further Development ...................................................... 182 Annex I - Occupancy Profiles – OP1-OP2 .................................................... 186 Annex II - Questionnaire............................................................................. 187 References ................................................................................................. 195 iii.

(8) Abstract This thesis focus on research activities within the context of the development of a Near Zero Energy (NZE) settlement in a real case study in Italy. This study is part of a wider research project called ZERO-PLUS (acronym of “Achieving near Zero and Positive Energy Settlements in Europe using Advanced Energy Technology”), which is in the International Horizon 2020 programme. The project involves the construction of four real-life case study NZE settlements in Europe, i.e. in Italy, France, Cyprus, and UK. In particular, the Italian settlement is composed of advanced solutions for the building envelope, innovative energy production systems, and integrated resources energy management at the settlement level. However, the objective of obtaining high performance energy buildings can be reached only if considering the contemporaneous influence of technical characteristics and occupancy. Recent studies report that as buildings become more energy efficient, the behavior of occupants plays an increasing role in energy consumption. Therefore, a construction designed to be a Net Zero Energy Building (NZEB) might consume higher than expected if the occupant behavior assumptions made in the simulation process are not respected during the real use. On the other hand, the effective performance of innovative and high efficiency technologies must be checked against predicted performance. In this view, one of the goals of this study is to highlight the critical points that may affect the energy performance, real and expected, of new buildings aimed at meeting the net zero energy standard. The analysis has, therefore, been performed through calibrated dynamic simulation of a continuously monitored building. In detail, indoor comfort settings by the occupants and their interaction with the envelope and the systems directly affect the operation of buildings and related energy uses. Simulation tools (EnergyPlus and DesignBuilder) were employed to demonstrate the potential impact of occupant behavior lifestyles and different household compositions on energy use and thermal comfort conditions. The results clearly reveal their impact. The savings in terms of annual energy consumption can reach up to 60% in the transition from wrong to "green" behaviour. Indeed, this study aims at focusing the attention on the urgent need of reference models related to human behaviors that influence the energy use in buildings, especially in NZEBs. Finally, the importance of psychological factors is also increasingly being recognized in driving the NZEB movement. This study develops an extended Technology Acceptance Model (TAM) to explain consumers' intention to adopt NZEBs in NZE settlement framework and examines it through an extensive survey conducted via social media channels. The results show that subjective knowledge, perceived usefulness, perceived climate change, attitude towards NZEBs in NZE settlement framework and general environmental concern measured by the New Ecological Paradigm (NEP) scale, are the significant psychological determinants of intention to adopt NZEBs in NZE settlement framework. It is also found that lacking subjective knowledge related to NZEBs, and in particular NZE 1.

(9) settlements, could be a potential psychological barriers among the surveyed consumers. The identified psychological factors provide references for policymakers to effectively develop consumers' behavioral intervention strategies and allocate resources in NZE settlements promoting schemes.. Sintesi Le attività di ricerca descritte in questa tesi si focalizzano sullo sviluppo dei quartieri ad energia netta zero (NZE settlements) in un caso di studio reale in Italia. Questo studio fa parte di un più ampio progetto di ricerca chiamato ZERO-PLUS (acronimo di “Achieving near Zero and Positive Energy Settlements in Europe using Advanced Energy Technology”), che fa a sua volta riferimento al programma internazionale Horizon 2020. Il progetto prevede la costruzione di quattro quartieri NZE in casi di studio reali in Europa, cioè in Italia, Francia, Cipro e Regno. In particolare, l'insediamento italiano è composto da soluzioni avanzate per l'involucro edilizio, sistemi innovativi di produzione di energia e gestione integrata delle risorse energetiche a livello di quartiere. Tuttavia, l'obiettivo di ottenere edifici ad alte prestazioni energetiche può essere raggiunto solo se si considera l'influenza contemporanea delle caratteristiche tecniche e dell'occupazione. Studi recenti riportano che, man mano che gli edifici diventano più efficienti dal punto di vista energetico, il comportamento degli occupanti gioca un ruolo sempre più importante nel consumo. Pertanto, una costruzione progettata per essere un “Net Zero Energy Building” (NZEB) potrebbe generare un consumo maggiore del previsto se le ipotesi fatte nel processo di simulazione non sono rispettate durante l'uso reale. D'altra parte, le prestazioni effettive di tecnologie innovative e ad alta efficienza devono essere verificate rispetto alle prestazioni previste. In quest'ottica, uno degli obiettivi di questo studio è quello di evidenziare i punti critici che possono influenzare le prestazioni energetiche, reali e attese, di nuovi edifici volti a soddisfare lo standard di energia netta zero. L'analisi è stata quindi eseguita attraverso la simulazione dinamica calibrata di un edificio continuamente monitorato. Nel dettaglio, le impostazioni dei parametri di comfort da parte degli occupanti e la loro interazione con l'involucro e i sistemi influenzano direttamente il funzionamento degli edifici e i relativi usi energetici. Gli strumenti di simulazione (EnergyPlus e DesignBuilder) sono stati impiegati per dimostrare il potenziale impatto degli stili di vita degli occupanti e delle diverse composizioni domestiche sull'uso di energia e sulle condizioni di comfort termico. I risultati rivelano chiaramente il loro impatto. I risparmi in termini di consumo annuale di energia possono arrivare fino al 60% nel passaggio da comportamenti errati a "verdi". Infatti, questo studio mira a focalizzare l'attenzione sull'urgente bisogno di modelli di riferimento relativi a problemi comportamentali umani che influenzano l'uso di energia negli edifici, in particolare negli NZEB. Infine, l'importanza dei fattori psicologici viene sempre più riconosciuta nel guidare il movimento NZEB. Questo studio sviluppa un esteso “Technology Acceptance Model” (TAM) 2.

(10) per spiegare l'intenzione dei consumatori di adottare gli NZEB nel contesto dei quartieri NZE lo esamina attraverso un'ampia indagine condotta attraverso i canali dei social media. I risultati mostrano che la conoscenza soggettiva, l'utilità percepita, i cambiamenti climatici percepiti, l'atteggiamento nei confronti degli NZEB nel contesto dei quartieri NZE e le preoccupazioni ambientali generali misurate dalla scala “New Ecological Paradigm” (NEP), sono i determinanti psicologici significativi dell'intenzione di adottare gli NZEB nel contesto dei quartieri NZE. Si è anche riscontrato che la mancanza di conoscenze soggettive relative agli NZEB, e in particolare ai quartieri NZE, potrebbe costituire una potenziale barriera psicologica tra i consumatori intervistati. I fattori psicologici identificati forniscono riferimenti ai responsabili politici per sviluppare efficacemente strategie di intervento comportamentale per i consumatori e allocare risorse negli schemi di promozione dei quartieri NZE.. 3.

(11) Introduction Net zero energy communities are the next frontier in energy efficiency and sustainability, paving the way for the development of future smart cities. Net Zero Energy (NZE) Settlements with a reduced carbon footprint will play a key role in fulfilling the EU’s ambitious targets. Achieving net zero energy at the settlement scale represents a unique challenge as well as opportunity. NZE settlements should be places of advanced social progress and environmental regeneration, as well as places of attraction and engines of economic growth based on a holistic integrated approach in which all aspects of sustainability are taken into account. They will also support the efficient use of natural resources, economic efficiency and the energy efficiency in new and existing buildings. This study is part of a wider research project called ZERO-PLUS (acronym of “Achieving near Zero and Positive Energy Settlements in Europe using Advanced Energy Technology”), which is in the International Horizon 2020 programme. The project has the aim to develop a comprehensive, cost-effective modular system for NZE settlements, focuses mainly on occupants' behaviour and consumers' willingness towards these types of projects. Nowadays, the construction sector is responsible for about 40% of the energy demand in EU and it is the main contributor to greenhouse gas (GHG) emissions (O’Brien et al. 2016). A correct assessment of the energy request is a challenge of primary importance since it influences both the environmental and the economic aspect. To this aim, occupants’ presence and behaviours inside buildings are the main causes of energy consumption prediction gap. When wrong evaluations concern low-energy buildings, additional issues are generated. Near-zero and zero energy buildings should satisfy precise requirements in terms of energy demand and indoor comfort conditions and, as a consequence, users’ expectation is very high. The correct representation and integration of the human component inside simulation software is an essential step to enhance the simulation results, reduce the gap between real and predicted energy consumptions, improve building design quality, control, and operation. In Net Zero Energy Buildings (NZEBs), particularly, the high variability of various parameters affecting the reliability of the simulation model, could cause non-negligible discrepancies between simulated and real data. Therefore, dynamic simulation models require a preliminary calibration and validation based on continuously monitored data. Without strong market demand, developers would not have motivation to develop NZE settlements. Driven by sustainable development worldwide, consumers have gradually changed their views and interests in the products they buy. One prerequisite to market demand is the acceptance by residents, who are the final buyers and consumers of the. 4.

(12) residential buildings and, hence, have a large influence on the future development of NZEBs. Thus far, determinants significantly affecting consumers’ purchasing intention and the relationship between these determinants and purchasing intention of NZEBs remain unclear. In this view, the present thesis employs the social psychological model to investigate consumers’ purchasing intention of NZEBs in the NZE settlements framework.. Figure 1: Workflow of the thesis. The workflow of the thesis is presented in Figure 1 and summarized in the following steps. The first part presents the research background by introducing the concepts of NZEB and NZE settlement (Chapter 1) and by describing the ZERO-PLUS project (Chapter 2). More in detail, Chapter 1, in addition to summarizing several examples from literature of NZEB and NZE settlements, highlights the importance of energy prevision accuracy for this type of buildings. Furthermore, it introduces the phenomena related to climate change, urbanisation, and Urban Heat Island (UHI). In Chapter 2, instead, the four real case studies settlements involved in the ZERO-PLUS project throughout Europe, i.e. in Italy, France, 5.

(13) Cyprus and UK, and the innovative technologies implemented at building and settlement level are described. In addition, the design and optimization results of the Italian case study are summarized. Moreover, in Chapter 3 the concepts and variables related to the evaluation of comfort for human body and the indoor environment are shown, following the scientific literature. In particular, the chapter includes: the ergonomics of the thermal environment and the variables that describe the physiological behavior of the human body on the Thermal Comfort and the Indoor Air Quality (IAQ) and the sensation indexes of Thermal Comfort. Therefore, Chapter 4 reports the procedure of the pre-occupancy checks followed to evaluate the actual performance of the case study NZEBs. This procedure is part of the project’s standard Monitoring and Verification (M&V) plan. Selected monitoring results are implemented in the thermal-energy dynamic simulation software for the case study building model calibration and validation(Chapter 5). In Chapter 6, the potential effect of different occupant behaviour lifestyles on energy use and comfort condition is shown within calibrated models. In detail, in addition to various family compositions, three occupant behavior lifestyles (high, standard, and low consumer) are introduced and evaluated by considering significant interactions between users and the building envelope/systems. Chapter 7 develops an extended Technology Acceptance Model (TAM) to examine the role of psychological factors on consumers' acceptance of NZEBs included in the NZE settlements framework and examine it in a survey conducted via social media channels. Structural equation modeling (SEM) using the analysis of moment structures (AMOS 22) software developed by IBM corporation was employed to analyze the collected data. Finally, the last chapter of the thesis reports the main conclusions and future developments of the work.. 6.

(14) CHAPTER 1 Towards Net Zero Energy Settlements. 1.1 Energy Consumption in the European Built Environment Globally, buildings consume over one third of all final energy and half of all electricity, and as a result they are also responsible for about one third of global carbon emissions [2]. In Europe, 27% of final energy use occurs in residential buildings and another 14% in tertiary buildings, making the "building sector" the largest end-use energy consumer with over 40% of the total [3]. If we account for the energy that is "embodied" in the production of these buildings and their materials, together with that which is required for urban mobility, then it becomes clear that the majority of society's demand for energy can be attributed to the built environment.. Figure 1.1 Share of buildings in final energy consumption [4]. The energy consumed annually within European buildings averages about 220 kilowatts per square meter – though this figure varies from only 150 kW/m2 in Bulgaria and Spain to as much as 320 in Finland, and from 200 kW/m2 in dwellings to nearly 300 in non-residential buildings. The bulk of this demand is typically for heat, with space heating accounting for over 70% of household consumption and water heating for another 12%. While air conditioning and other appliances currently account for only 15% of the total, the use of energy-intensive AC is rapidly increasing, especially in southern European countries: in the short period from 2005 to 2009, for example, energy consumption for cooling increased by 30% in Spain and Italy and doubled in Bulgaria [4]. In fact, the energy demand for space heating and cooling varies substantially between regions due to differences in local climate. 7.

(15) and the quality of the building stock, contributing to differences between EU countries in terms of the role played by buildings in their overall consumption (Figure 1.1). Despite the significant improvement of the energy efficiency, (1.4% per year), the energy consumption of the residential buildings in Europe increased by 14% between 1990 and 2012. At the same time the electricity use increased by 60% because of the very rapid penetration of electronic appliances and devices. Increase of the energy consumption is attributed to various economic, social, political and technical reasons. A major driver increasing the energy consumption of buildings is related to the significant increase of the number of households in Europe. In parallel, the size of dwellings has increased considerably during the last years in most of the European countries as a result of the significant increase of the household income, reaching about 0.9%/year over the period 1995–2009. Specifically, during the years between 1997 and 2009, the average size of the dwellings increased by 3% [4]. Although the total energy consumption of buildings has increased, the specific consumption for heating purposes has decreased to about 15% during the period 1997–2009. This may be attributed to the considerable lower consumption of the new dwellings built after 1997, representing almost 20% of the total dwelling stock in 2009. New dwellings consume almost 30–60% less thermal energy than houses built before 1990 [4]. Lower energy consumption for heating purposes is the result of the new, efficient legislation applied in many European countries [3]. 1.1.1 Climate Change and Urbanization in Europe Climate change is a major issue for Europe. Increase of the ambient temperature and higher frequency of heat waves have an important impact on the energy consumption and environmental quality of the built environment and increase the vulnerability of the local population [3]. Climate change is occurring in Europe as mean temperatures have increased and precipitation patterns have changed (Alcamo et al. 2007). Climate change is a stress factor for cities and ecosystems, whereas climate-related extreme weather events, such as cold spells and heat waves, result in health and social impacts in Europe and may impact considerably urban infrastructure and the built environment (EEA 2012). High temperature extremes (hot days, tropical nights, and heat waves) have become more frequent (Vautard et al. 2013), while low temperature extremes (cold spells, frost days) have become less frequent in Europe (EEA 2012). Climate models show significant agreement in warming, with the strongest warming in southern Europe in summer (Giorgi and Bi 2005; Hertig and Jacobeit 2008; Goodess et al. 2009). The likely increase in the frequency and intensity of heat waves, particularly in southern Europe, is projected to increase heat-attributable deaths unless adaptation measures are undertaken (Baccini et al. 2011; WHO 2011a, b; IPCC 2014). Without adaptation, between 60,000 and 165,000 additional heat-related deaths per year in the EU are projected by the 2080s, depending on the scenario (Ciscar et al. 2011). 8.

(16) Finally, even under a climate warming limited to 2 °C compared to pre-industrial times, the climate of Europe is projected to change significantly from today’s climate over the next few decades (Van der Linden and Mitchell 2009).. Figure 1.2 A combined view of “Aggregate potential impact of climate change,” “Overall capacity to adapt to climate change,” and “Potential vulnerability to climate change” for the Mediterranean area (EEA 2012). In Figure 1.2, a combined view of “Aggregate potential impact of climate change,” “Overall capacity to adapt to climate change” and “Potential vulnerability to climate change” is provided (EEA 2012). The Mediterranean area, including urban areas, shows, overall, medium negative potential impact; coastal areas in Spain and coastal/inland areas in Italy 9.

(17) show the highest negative potential impact of climate change. Furthermore, the Mediterranean area shows medium to highest vulnerability to climate change (in the same overall areas as before), a fact that if linked to the limited capacity to adapt to climate change, reflects the sensitivity of the area in climate change and the urgent need to adapt measures in full temporal and spatial scales and a wide sectoral range. [5] Environmental perturbations and global climate change have an important impact on the energy consumption of the building sector in Europe. Several studies have investigated the past and future impact of climate change in different parts of Europe (Cartalis et al., 2001; Asimakopoulos et al., 2012; Kapsomenakis et al., 2013; Ciscar et al., 2014). Most of the studies predict an important decrease of the heating demand and a very significant increase of the energy used for cooling purposes. The future heating and cooling energy demand of buildings in Europe is simulated for the period 2010–2050 using four different climatic scenarios (Ciscar et al., 2014). It is reported that the average heating energy may decrease between 9 and 17, while the corresponding cooling energy needs may increase by approximately 40–70% depending on the scenario considered. Decrease of the heating demand is more significant in the European North, while the European South may experience the higher increase of the cooling needs. [3] Energy consumption for cooling is increasing rapidly in most of the Southern European countries. The highest cooling energy consumption is presented in Cyprus, where dwellings are spending about 670 kW h/year, followed by Malta with 540 kW h/year. Very high increasing rates are observed in most of the southern European Countries because of the very rapid penetration of air conditioners. In particular, between 2005 and 2009 the energy consumption for cooling has increased almost by 100% in Bulgaria, and by 30% in Spain and Italy [4]. Climate change interacts with urbanization, population aging and socio-economic issues; it also interacts with the economic development of cities. As cities influence to considerable extent Europe’s economy, any climate-related problems may place Europe’s economy and quality of life under threat. Nearly 73% of the European population lives in cities, and this is projected to reach 82% by 2050 (United Nations 2014). Urbanization is associated with changes in materials and energy flow in the cities (Chrysoulakis et al. 2013), can increase pressures on the environment, and may support climate change mechanisms through enhanced emissions of greenhouse gases. It may also reduce the resilience of cities to extreme events associated with climate change due to urban land take and the limited capacity to regenerate the building stock of the cities. [5] Figure 1.3 shows the population of predominantly rural regions is projected to fall by 7.9 million inhabitants during this period, to account for 20% of the EU-28 population by 2050. Although the number of people living in intermediate regions is projected to rise by 1.1 million persons, their share of the overall number of inhabitants in the EU-28 is predicted to fall to 34.2% by 2050.. 10.

(18) Figure 1.3: Urban-rural population projections, EU-28, 2015–50 (million inhabitants) Source: Eurostat. By contrast, the projections foresee the total number of people living in predominantly urban regions rising by 24.1 million persons, and that by 2050 these regions will provide a home to almost half (45.8%) of the EU-28 population [6]. Cities are major contributors to CO2 emissions. Roughly half of the world’s population lives in urban areas; this share is increasing over time and is projected to reach 60% by 2030. Cities consume most—between 60 and 80%— of the energy production worldwide and account for a roughly equal share of the global CO2 emissions. GHG emissions in cities are increasingly driven less by industrial activities and more by the energy services required for lighting, heating and cooling, appliance use, electronics use, and mobility. Growing urbanization will lead to a significant increase in energy use and CO2 emissions, particularly in countries where urban energy use is likely to shift from CO2-neutral energy sources (biomass and waste) to CO2 intensive energy sources. [5] 1.1.2 The Urban Heat Island (UHI) Effect: Causes and Mitigation Strategies The relationship between climate change and cities is rather complex and some of the challenges that planners will have to face, especially in terms of mitigation and adaptation, can be identified with the effects of climate change. The contrast with the Urban Heat Islands (UHI) is one of the most obvious, intensified by global warming, which in the coming years will also have to be addressed structurally by urban and territorial planning [7]. Generally, the term “heat island effect” describes the characteristic warmth of both the atmosphere and the surfaces in developed urban areas compared to their (non-urbanized) surroundings, usually the nearby underdeveloped or undeveloped suburban and rural areas. The annual mean air temperature of a city with 1 million people or more can be 1.8– 5.4°F (1–3°C) warmer than its surroundings. On a clear calm summer night, however, the 11.

(19) temperature difference can be as much as 22°F (12°C). The heat island is an example of unintentional climate modification when urbanization changes the characteristics of the Earth’s surface and atmosphere.. Figure 1.4: Variations of Surface and Atmospheric Temperatures. The heat island sketch pictured in Figure 1.4 shows how urban temperatures are typically lower at the urban-rural border than in dense downtown areas. The graphic also shows how parks, open land, and bodies of water can create cooler areas within a city. In addition to the overall city-wide (urban-level) global effect, the term “heat island” also describes a site-level localized effect, that is, the built-up areas that are hotter than immediately nearby surrounding areas (e.g., a building or parking lot or an airport surrounded by open areas with bare natural soils or vegetation), creating hot spots. The local effect usually is much more severe than at the global scale owing to the higher local temperature and more direct impacts on pedestrians, buildings, and vehicles. [8] The most significant cause of the UHI is urbanisation. The constant increase in hard and heat absorbing surfaces, the density of our cities, and the reduction in natural vegetation are the main contributors to the heat island effect (Akbari et al., 2001; Doulos et al., 2004; Rossi et al., 2014). Takebayashi and Moriyama (2012), in their study of surface heat budget of various pavement materials in Japan, show that the daytime temperature of normal asphalt can be up to 20°C hotter than grass. The changes in our cities mean that the amount of vegetation is decreasing, and pavements now cover an increasingly high proportion of our cities, contributing significantly to the heat island phenomenon (Santamouris, 2013b). The network of paved surfaces and roads that our cities are increasingly developing, have 12.

(20) been shown to account for a larger percentage of elevated surface temperatures per unit volume compared to any other man made material or structure (Golden and Kaloush, 2006). In particular, due to the large amount of concrete and asphalt in cities, the difference in average annual temperatures compared to rural areas ranges from 3.5 to 4.5°C (up to a difference of 10°C in large cities), and is expected to increase by 1°C per decade (Santamouris 2007; Stone et al. 2010). The cities of today continue to increase in size and breadth; a phenomenon known as urban sprawl. Stone et al. (2010) illustrate that urban sprawl contributes to an increasing number of heatwaves, and sprawling cities result more frequently in extreme heat events when compared with compact metropolitan cities. According to the United Nations Population Fund, cited in Stempihar et al. (2012), by 2030, 61% of the world's population will live in cities. Rapid increases in the world's population is also a key driver of change in the urban and global environment through global warming, loss of biodiversity and deforestation (Grimmond, 2007). The increase in the use of engineered materials in our cities, which have greater heat storage capacity as well as lower albedo, and the associated reduction in native vegetation, have a major influence on the UHI effect (Golden and Kaloush, 2006). The hydraulic, radiative and thermal characteristics of materials used in modern construction are completely different in comparison to natural soil and rock, vegetation, and water (Grimmond, 2007). The changing materials result in new surface and atmospheric conditions, thereby altering the exchange of energy and water, as well as the airflow. In addition, combining these changes in the conditions with the anthropogenic heat from vehicles and people, increased pollution, and the increased density of our cities, results in a completely different and distinct urban climate today (Landsberg, 1981; Oke, 1997; cited in Grimmond, 2007). Technological developments within society contribute to the UHI effect through increased heating and cooling. The most significant are air conditioning systems, which, although effective for increasing human comfort, inherently generate a greater level of heat (Grimmond, 2007). Given the density of today's cities, there are a larger number of air conditioners that are essential for the functioning of buildings and structures. Our increasingly hotter climate sees the use of more air conditioners, which significantly increase the heat of a city, creating thermal discomfort, more greenhouse emissions, and affecting human wellbeing (Rossi et al., 2014). In addition to this, electricity demand for heating and cooling as a result of UHI has a significant effect, with Akbari et al. (2001) finding that for each 1°C increase in temperature, electricity demand increases by between 2 and 4%. Figure 1.5 below illustrates the relationship between atmospheric heat, increased use of manufactured materials, and various other causes that can be attributed to the UHI. [9]. 13.

(21) Figure 1.5: How the Urban Heat Island occurs - image sourced from (Yamamoto 2006). The UHI effect has significant consequences for the liveability in our cities, and is the source of a significant number of environmental problems in urban areas (Yang et al., 2015). The warming effect of urbanisation has critical impacts on health and wellbeing, as well as human comfort and the local atmosphere (Grimmond, 2007). Ichinose et al. (2008), Synnefa et al. (2011), and Yang et al. (2015), illustrate the various consequences associated with the UHI effect; these include: • Increased cooling energy usage and associated costs; • Significant increases in peak energy demand; • The formation of large amounts of smog and air pollutants, and a resulting degradation in the quality of air; • Increased thermal stress on residents and the public; • Strong impact on urban ecosystems; • A living environment that is significantly degraded; • A significantly increased level and risk of morbidity or illness due to heat. Urban overheating produced by UHI has a dangerous impact on citizens’ health conditions and indoor-outdoor comfort perception, affecting their quality of life and economic wellbeing and, therefore, having a non-negligible modification of the urban environment from multiple perspectives (Kolokotsa, Santamouris 2015). The negative impact of elevated temperatures on urban infrastructure, ecosystems, and human health and comfort provides the motivation for finding UHI mitigation measures. In particular, the most sensitive people to this environmental change are low income and vulnerable population living in dense urban areas (Sakka et al. 2012; Santamouris et al. 2014). Sakka et al. (2012) showed that the extended exposure to hot thermal conditions, as registered during the heat wave of 2007 in South-Eastern Europe, produced dangerous 14.

(22) indoor thermal overheating in buildings with low technical quality, in particular. More in details, the authors measured that the average indoor temperature of all the monitored residential units was almost 4.2°C higher than the average indoor temperature registered in standard summer conditions in Athens, i.e. before and after such heat wave period, exacerbated by UHI in Athens. Additionally, the relatively low awareness and education level of low income households with respect to the correct use of passive cooling strategies for improving indoor thermal conditions make them even more vulnerable against summer heat wave events and UHI in general. In this view, key research contributions were focused on the identification of UHI effect on energy poor population, where the core of the analysis was focused on the impossibility of households to provide for the necessary environmental active systems, aimed at addressing cooling and heating elementary needs (Santamouris et al. 2012; Plan Batiment Grenelle 2009). In this view, statistics also showed that energy poor people are used to live in buildings characterized by low quality performance envelope mainly produced by poor thermal insulation and inertia, non-effective shading systems and high infiltration rate (Plan Batiment Grenelle 2009). According to the European Commission (Saheb et al. 2015), as of the year 2012 a full 11% of the population were unable to keep their homes warm in the winter, and 19% lived in dwellings they could not keep comfortably cool in the summer. Therefore, the combination of energy poverty and weak availability of effective passive systems make low-income households even more vulnerable against the UHI phenomenon in dense cities all over the world. Furthermore energy poor European population spends about 40% of their total income on housing running costs, that is 30% more than the average European population (Kolokotsa, Santamouris 2015). [10] In (Matzarakis, Amelung, 2008), effects of the thermal environment on humans are determined through the application of thermal indices based on the energy balance of the human body. The most important of them are PMV (Predicted Mean Vote) (Fanger, 1972), PET (Physiologically Equivalent Temperature) (Matzarakis, 1999), and SET* (Standard Effective Temperature) (Gagge et al.,1986) [11]. Detailed descriptions of human body energy balance and comfort thermal indices can be found on Chapter 3. Santamouris (2013b) also illustrates that various studies have been able to measure significant increases in urban temperatures resulting in double the cooling energy usage of buildings. [9] Intensified air-conditioning loads lead to higher peak power demand (Santamouris et al. 2015) and strained electricity supply systems (EU, 2013), inducing utilities to invest in additional generating capacity and infrastructure and pass the costs on to consumers – who must also install larger HVAC systems to maintain a given level of comfort (Santamouris et al., 2001). As nocturnal urban heat islands limit the effectiveness of night ventilation (Geros et al. 1999), large segments of the population who have traditionally relied on and other passive cooling techniques are compelled to either install energy-intensive AC or become 15.

(23) susceptible to increased health risks during prolonged heat waves (Dousset et al. 2011) (Laaidi et al. 2012). Finally, energy consumption in buildings can have a range of impacts on the susceptibility of a population to energy poverty, as it affects running costs for heating and cooling as well as health-related expenditures for vulnerable populations (Santamouris 2016). [12] Thus the issue of energy consumption in the built environment is closely linked with many of the pressing economic as well as environmental challenges affecting society. The multiple and varied synergies and interdependencies between these realms were recently mapped out by Santamouris (2016), particularly with respect to local climate change and energy poverty. In terms of the impact of building energy efficiency on climate, these interactions include the emission of anthropogenic heat and CO2 resulting from the use of HVAC systems and from fossil fuel-based power generation (Hamilton et al. 2009), and their effect on urban temperatures (McCarthy, 2009; Bohnenstengel et al. 2014). The relation between energy efficiency and actual consumption is compounded by "rebound effects", by which improvements in thermal efficiency drive down energy costs, and in turn can encourage increased per capita consumption – thereby offsetting potential reductions in overall energy use and emissions (Bourrelle, 2014; Cellura et al. 2013; Greening et al. 2000). [12] As evidenced by Santamouris et al. [13], it becomes increasingly important to study urban climatic environments and to apply this knowledge to improve people’s comfort and decrease the energy consumption in cities. In the above-mentioned paper, the energy impact of higher ambient temperatures in the city centers due to the urban heat island effect is carried out; in particular, as a consequence of the UHI phenomenon, the cooling load of urban buildings may be doubled, the peak electricity load for cooling purposes may be tripled especially for high set point temperatures, the minimum Coefficient Of Performance (COP) value of air conditioners may be decreased up to 25%, while in winter the heating load of urban buildings may be reduced up to 30%. Many other recent studies have analyzed the strong impact of UHI on building’s energy consumption: in [14] is found that electricity demand for cooling increases 3% to 5% for every 1°C increase in air temperature above approximately 23°C ± 1°C. This fact clearly show that a 5°C UHI can increase the urban electric power consumption for cooling by 15% to 25% with respect to rural areas. In [15] is demonstrated that the increase in air temperatures over the last decades is responsible for 5 to 10% of urban peak electric demand for a/c use, so this amount of energy is used to compensate for the heat island effect. Heatwaves are responsible for a range of serious health issues, and, at their extreme, can account for a large number of fatalities. In particular, mortality for populations in the European Union has been estimated to increase by 1 to 4% for each degree increase of temperature above a (locally specific) cutoff point (WHO 2011).. 16.

(24) Furthermore, urban air pollution concentrations increase in warming cities (Stathopoulou et al. 2008; Taha 2008); they may also increase during heat waves with significant consequences for mortality. This is due to the fact that high temperatures and solar radiation stimulate the production of ozone as well as volatile organic compounds (VOCs). Under existing air pollution abatement policies 311,000 premature deaths are projected in 2030 due to ground-level ozone and fine particles (EEA 2006). Hatvani-Kovacs et al. (2016) argue that an emphasis on the public health risks of heatwaves outweighs discussion on the water and electricity usage. [16] In the United States, the Environmental Protection Agency (EPA) has developed a threepronged approach of cool pavements, urban forestry and vegetation, and cool roofs and green roofs to mitigate the UHI. Including the approaches developed by the U.S. EPA, communities can take a number of potential steps to reduce the local and/or atmospheric heat island effect, such as the strategies listed below based directly on the causes of the heat island [8]: 1. Increasing tree and vegetative cover; 2. Creating green roofs (aka “rooftop gardens” or “eco-roofs”); 3. Installing cool mainly reflective roofs; 4. Using “cool” pavements; 5. Introducing water bodies into the urban area; 6. Reducing anthropogenic heat (released waste heat from heating/cooling, etc.); 7. Improving urban geometry to improve air flow and enhance the natural ventilation. The last three decades have witnessed significant research and development activities in understanding urban heat islands, their environmental effects, their health impacts, development of measures to mitigate heat islands, and development of implementing policies and programs to cool urban heat islands. The research was initially focused on recognizing that the cities are warmer than their suburban areas, noting that these elevated temperatures are because of urban fabric, and investigating the potential changes in the urban fabric, (changing urban surfaces and adding urban vegetation), would affect the summertime energy use in urban buildings (Akbari 1992). The research identified that cool roofs and shade trees directly reduce cooling energy use in buildings and combination of cool roofs, cool pavements, and urban vegetation will cool the city by a few degrees (Akbari 1992). Cooling cities, (lower ambient temperatures), further decreases cooling energy use in buildings, make the outdoor pedestrian environment more comfortable, and slow down the smog photochemical reactions (see fig. 1.6). Cool roofs and shade trees reduce air conditioning energy use leading a lower demand for power, lower consumption of fuel, lower air pollutants and greenhouse gas emissions. Cool roofs, cool pavement, and urban vegetation cool the city and reduce formation of smog. Cool roofs and cool pavements reflect shortwave radiation back to space and induce a negative radiation forcing.. 17.

(25) Figure 1.6: Effects of heat island countermeasures [16]. Building energy simulations in many climates quantified the potential cooling energy savings and electrical peak demand reductions in many climates. The analysis concluded that cool roofs saves the energy consumption related annual expenditures in all buildings that need cooling during the summer and winter heating penalties are only a fraction of summer cooling savings. In some climates, installing a cool roof precludes the need to buy air conditioning. These simulations were validated with many field experiments documenting cooling energy savings of 10–50% (depending on climate, building type and operation) for the area under the roof (Synnefa et al. 2012). The potential benefits of cool roofs and heat island measures were further investigated in cold climates (Hosseini, Akbari 2014; Mastrapostoli et al. 2014). The moisture transfer in roofing layers were studied and concluded that roofs were not different from walls in terms of their moisture transfer. Installing a cool roof does not create moisture problems on properly engineered design and constructed to the code. In addition, accumulated snow on the roof significantly reduces potential winter heating penalties in cold climates (a white and a black roof covered with snow perform the same). [16]. 1.2 Net Zero Energy Buildings In response to a growing perception that the trajectory of energy use patterns in buildings is not sustainable, the European Union has established specific policies aimed at reducing fossil fuel consumption and their related greenhouse gas (GHG) emissions. Achieving the transition to low-carbon buildings would need to be carefully planned within the context of the broader energy sector, to avoid unnecessary costs or early retirement of existing capital (e.g. natural gas networks and recent installations of gas equipment in buildings).. 18.

(26) This would require a combination of policy packages, market frameworks (including financing mechanisms) and planning tools, such as heat mapping and urban planning, to facilitate a smooth shift away from fossil fuels over the coming decades. To pursue goals within a coherent long-term strategy, the EU has formulated targets for 2020, 2030, and 2050. The 2020 Energy Strategy defines the EU's energy priorities between 2010 and 2020. It aims to: • reduce greenhouse gases by at least 20%; • increase the share of renewable energy in the EU's energy mix to at least 20% of consumption; • improve energy efficiency by at least 20%. EU countries have agreed that the following objectives should be met by 2030: • a binding EU target of at least a 40% reduction in greenhouse gas emissions by 2030, compared to 1990; • a binding target of at least 27% of renewable energy in the EU; • an energy efficiency increase of at least 27%, to be reviewed by 2020 with the potential to raise the target to 30% by 2030; • the completion of the internal energy market by reaching an electricity interconnection target of 15% between EU countries by 2030, and pushing forward important infrastructure projects. Together, these goals provide the EU with a stable policy framework on greenhouse gas emissions, renewables and energy efficiency, which gives investors more certainty and confirms the EU's lead in these fields on a global scale. On 30 November 2016, the Commission released a package of draft legislative proposals designed to help achieve these targets. The measures include draft proposals on electricity market design, renewables, and energy efficiency. The EU aims to achieve an 80% to 95% reduction in greenhouse gases compared to 1990 levels by 2050. Its Energy Roadmap 2050 analyses a series of scenarios on how to meet this target [17]. In this context, the topic of sustainable, zero energy buildings (ZEBs) has become increasingly important, as evidenced by the international effort on the subject. In Europe, zero energy buildings are considered the logical continuation of a long chain of developments from low-energy houses towards passive houses. The amendment to the EU Energy Performance in Buildings Directive (EPBD) prominently addresses the related subject matter. The first directive in 2002 initiated the introduction of integrated energy balancing methods throughout Europe. These were required to take air conditioning, lighting, and use of renewable energy into account. In the 2010 recast [18] the European Commission introduced the term “near zero energy building” and specified timeframes for the implementation of related construction standards within its member states. • “Article 2: Definitions: Nearly zero-energy building means a building that has a very high energy performance …. The nearly zero or very low amount of energy required 19.

(27) should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby. • Article 9: Nearly Zero Energy Buildings: Member States shall ensure that: a) by 31 December 2020, all new buildings are nearly zero-energy buildings; b) after 31 December 2018, new buildings occupied and owned by public authorities are nearly zero-energy buildings”. Member States shall draw up national plans for increasing the number of nearly zeroenergy buildings. These national plans may include targets differentiated according to the category of building. Respecting to this, the main European countries have adopted energy strategy goals in line with the EU ones, taking into account the environmental and decarbonisation targets. In Italy, the EPBD directive was implemented with Legislative Decree 192/95 and subsequent amendments, while the EBPD Recast was implemented through Law 90/2013, whose implementation decrees were issued in 2015. In the Italian framework, the Economic Development Ministry has set the National Energy Strategy (NES) meeting the European requirements and setting the following actions to be achieved by 2030, in accordance with the long-term scenario drawn up in the EU Energy Roadmap 2050 [19], which provides for a reduction of emissions by at least 80% from their 1990 levels. Here are the targets to be achieved by 2030 that are in line with the plan of the European Energy Union: • enhancing Italy’s competitiveness, by continuing to bridge the gap between Italian energy prices and costs and European ones, in a global context of rising energy prices; • attaining Europe’s environmental and decarbonisation targets by 2030 in sustainable ways, in line with the future targets set by COP2111: 2015 United Nations Climate Change Conference, also known as the Paris Climate Conference (21st Session of the Parties to the United Nations Framework Convention on Climate Change); • continuing to improve the security of energy supply and the flexibility of energy systems and infrastructures. The Energy Efficiency Directive, policies are defined for renovation of the existing building stock (e.g. 3% of governmental buildings per year) and for achieving energy savings equal to 1.5% per year, and through the parallel Renewable Energy Directive, sector-specific targets are set for the utilization of PV and other clean technologies. The Ecodesign Directive sets additional rules for energy-consuming equipment, and finally the Energy Labelling Directive defines requirements for the labeling of energy-efficient technologies used in buildings [3]. The energy efficiency legislation applied in many European countries has contributed to real reductions in consumption for heating purposes, with dwellings built in 2009 consuming 30-60% less on average than those built before 1990. These improvements are 20.

(28) especially apparent in Germany, Sweden, Denmark, Slovakia and the Netherlands, all of which saw reductions of more than 50% over this period [4]. The use of more energy efficient heating systems and fuels has also contributed to this trend, which has resulted in an average rate of decrease in heating energy consumption per dwelling of 1.4% per year. Despite these ambitious policy interventions, and actual improvements in the energy efficiency of buildings, the longer term trend is still toward increased overall consumption – which for residential buildings in Europe, grew by 14% between 1990 and 2012. One reason is the rapid market penetration of more and more electricity consuming devices, and another is the decrease in the number of occupants per household; that is, in most European countries, the size of dwellings per capita has substantially increased. Between 1997 and 2009 the average apartment size per inhabitant rose by 3% [4], and the rate of enlargement is even higher in France, Denmark and Germany. The impact of regulations on new buildings on the decrease of the average energy consumption per dwelling over the period 1990-2012 varies according to the countries, depending on the number of building code upgrades, their stringency and the volume of construction. It is estimated to explain around 30 to 40% at the EU level as well as in France, Italy, Denmark, the Netherlands and Poland, but only 14% of the decrease in Sweden. This modelling probably overestimates the impact of building regulations; indeed, it is well known, but not well quantified, that the actual specific consumption of new dwellings can be higher than this theoretical consumption because of non-compliance and rebound effects (i.e. the fact that in well insulated dwellings, occupants can afford to have a higher indoor temperature than in less insulated dwellings). [20] On these bases, the main expectations for future years, both at international and national level, regard having energy at a competitive cost, with a limited environmental impact and a high quality, ensuring the rapid diffusion of energy efficiency technologies and measures such as the development of net or nearly zero-energy buildings and settlements. The concept of Zero Energy Building (ZEB) has received growing international attention by the last years of 1990s, as proved by the increasing number of ZEB realizations and research projects on the topic. The design of buildings with a high energy performance, Low Energy Buildings, Nearly Zero Energy Buildings (NZEB) and Passive Houses must take into consideration all three of the aspects, building, technical systems and renewable energy sources, by adopting solutions with greater efficiency and/or performance in relation to the specific case: in other words, it is good to evaluate, each time, if it is preferable to act on the building envelope, technical systems, generator and so forth, in a continued iteration and interaction between architectural, technological and systems design, and the calculation results, without adopting extremist approaches, instead of adopting pre-arranged technological solutions or those copied from other examples, not always suitable for all contexts. [21] Achieving zero energy buildings means the optimization of passive design solutions, maximization of energy efficiency in order to minimize building’s energy needs and the implementation of on-site renewable energy sources. 21.

(29) Figure 1.7: The principles for Passivhaus with a heat recovery system and an air-based heat distribution system (heat generator is not shown) [22]. Shared strategies for reducing buildings energy consumption are based on the "Passive House" performance standards that, as can be seen in figure 1.7, are characterized by the following key concepts [22]: 1. Superinsulation and thermal bridge-free construction: all the building parts must have a very high level of insulation preventing thermal bridging and air leakage. Thick and continuous insulation keeps the inside cool in summer and warm in winter. 2. Compact form: the shape, size and orientation of a building can all have a significant impact on its useful energy requirements. The compactness ratio (SA/V ratio; SA: surface area of building envelope, V: volume of the building) has a pronounced influence on the heating and cooling demand, independently of the thermal transmittance value (U-value) of the building fabric. 3. Airtight building envelope: uncontrolled air leakage into and out of a structure occurs due to small holes and cracks in the building fabric as well as through poorly sealed windows and doors. Air leakage is driven by pressure differentials occurring between the inside and the outside of a building as a result of temperature differences, air currents and wind pressure. The consequences of air leakage include an increased demand for space heating and cooling, reduced comfort, draughts, and moisture convection. 4. Optimal use of passive solar gains; e.g. orientation, glazing ratios, daylighting: in winter, it is desirable to collect solar gains; however, in summer a large daylight opening often yields too much solar energy resulting in a thermally and visually uncomfortable environment. Proper solar shading and luminance screening has to be present for daylight openings on the south, east, and west orientations. In practice this means that the best shading systems permit a variable shading that responds to current climatic conditions (e.g. solar altitude), and are adjustable to weather and personal choices. 22.

(30) 5. Mechanical ventilation: balanced ventilation ensures fresh air—and controls moisture. All of this air tightening means that dirty, moist air isn't leaking into the living space, so air changes must be controlled with some sort of high-tech fan. One option is an energy recovery ventilator (ERV), which pulls new air in and pushes old air out while transferring heat and moisture in the process. In addition to optimising the energy efficiency of the building’s fabric and services, achieving clearly defined thermal comfort criteria is considered central to the concept. These functional definitions implies that the heat losses from a "Passive House" must be sufficiently low that only a very small amount of supplementary heating or cooling (added to the mechanical ventilation supply air) would suffice to cover the entire peak heating or cooling load. In order to ensure appropriate ventilation and to achieve a good level of indoor climate, efficient mechanical air ventilation must be provided. High levels of thermal insulation, the elimination of thermal bridges and significantly improved levels of airtightness are becoming the norm in modern forms of construction, and are a prerequisite for low energy buildings. Whilst this approach is designed to reduce unwanted heat losses and gains, it will also significantly alter the building envelope’s relationship with the external environment. Without forethought and an understanding of the mechanisms by which various environmental processes and materials interact, significant problems such as condensation and overheating can occur. Long-term condensation build-up, for example, can lead to structural degradation as well as negative impacts on indoor air quality. In the development of low energy building fabrics it is critical that structural integrity and occupant health are not compromised.. Figure 1.8: The Endesa Pavilion [23]. 23.

(31) An interesting example of a low-energy building is The Endesa Pavilion [23], a self-sufficient solar prototype installed at the Olympic Port of Barcelona as part of the World Congress of the Expo Smart City in Barcelona 2011. Essentially a wooden box, modules on the exterior walls fold out at different distances to create triangular protruding awnings whose exact angle and length are precisely calculated by the position of the sun, the need for shade, and the spatial requirements of the interior. Each section contains photovoltaic cells on top, which block out the sun over the window located underneath or on the downward-facing side. The inside of the forms create pockets for people or storage, effectively increasing the livable area on the same size footprint. The Endesa Pavilion has been entirely digitally fabricated by a group of researchers and students, and is able to generate twice as much energy than it needs to consume via flexible solar cells that are adjusted to the optimum form of the building. As a prototype, the pavilion researches the possibilities of combining traditional industry with contemporary digital fabrication techniques. In the context of achieving significant low energy transition in the building and housing sector, both the diffusion of existing technologies (Barnes 2016) and the emergence and diffusion of novel systemic and architectural innovations for residential buildings (e.g. Mlecnik 2013a) are needed. [24] 1.2.1 Net Zero Energy Building: Definition and Classification Recently, a prominent vision touted by so many stakeholders in the building sector proposes the so-called “net zero energy” buildings (NZEBs), buildings whose energy consumption are fully offset by renewable energy generated on site. Whether focused on new or existing buildings, achieving net zero energy involves three fundamental steps: optimize passive building design; maximize energy efficiency to minimize the building’s demand; then explore on-site renewable energy generation to cover the remaining energy needs. There are a number of definitions and strategies to achieving net-zero energy, but for NZEBs to become mainstream in the market, there is a need for a wide consensus on clear definitions, and agreement on the measures of building performance that could inform “zero energy” building policies, programs and industry building practices, as well as design tools, case studies and demonstration projects that would support industry adoption. [25] Over 82 national experts from 19 different countries have been directly involved in research project “IEA SHC Task 40 – ECBCS Annex 52: Towards Net Zero Energy Solar Buildings” [26] for over a 5-year period (October 2008 – September 2013). Their goal was to support the conversion of the Net ZEB concept from an idea into practical reality in the marketplace. The research team examined the many variations on the theme of Net Zero Energy that could be found in the literature as well as in the different participating countries. The goal was to discover a common language, and common performance metrics for what at first seems a simple concept: a Net ZEB is an energy grid-connected building which on an annual 24.

(32) basis contributes as much energy to the grid(s) to which it is connected as it draws from the grid(s). It is not an autonomous building standing alone and separate from a community. Rather, it is an integral part of that community, and its energy grids. [27] The tool can be of assistance for different stakeholders, including building designers (evaluation of building design solutions with respect to different Net ZEB definitions), energy managers (assess the balance in monitored buildings) and policy makers (assist in the upcoming implementation process of Net ZEBs within the national normative framework).. Figure 1.9: System structure and basic elements of NZEB [28]. The basic elements in definition of NZEB and their relationship are shown in figure 1.9 [28]. The basic elements are building system, energy grid and weighting system. In order to make a clear balance calculation for the net zero goal, a boundary need to be clarified for the building system with on-site renewable. Inside this boundary, building system consumes delivered energy, such as electricity, natural gas, from on-site renewable and energy grids, and output energy back to the grid when the REP (Renewable Energy Power) system generates excess electricity. Because of different design goals, different weighting systems are chosen to calculate the net energy obtained by the entire building system. For example, building owners typically care about energy costs, so they prefer to choose a weighting system in the cost balance, rather than the energy balance. Finally, weighted demand and supply are compared to check whether the net zero balance can be achieved based on the specific technology solution. This can be considered as the operating mechanism of basic NZEB evaluation. In addition to the basic elements and operating mechanism, the definition also involves some parameters, such as: boundary, weight, evaluation period. [29]. 25.