Comparative Analysis of Energy Demand and CO2 Emissions on Diﬀerent Typologies of Residential Buildings in Europe

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Article Comparative Analysis of Energy Demand and CO2 Emissions on Diﬀerent Typologies of Residential Buildings in Europe

Julià Coma 1 , José Miguel Maldonado 2 , Alvaro de Gracia 2,3, Toni Gimbernat 4, Teresa Botargues 5 and Luisa F. Cabeza 2,* 1 Departament de Tecnologia de l’Arquitectura, Universitat Politècnica de Catalunya, Av. Dr. Marañón 44-50, 08028 Barcelona, Spain; [email protected] 2 GREiA Research Group, INSPIRES Research Centre, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida, Spain; [email protected] (J.M.M.); [email protected] (A.d.G.) 3 CIRIAF—Interuniversity Research Centre, University of Perugia, Via G. Duranti 67, 06125 Perugia, Italy 4 SINAGRO ENGINYERIA S.L.P, Av. Estudi General 7, Altell 5, 25001 Lleida, Spain; [email protected] 5 USER FEEDBACK PROGRAM SL, Sant Jaume Apòstol 8, 25126 Almenar, Spain; [email protected] * Correspondence: [email protected]

Received: 21 May 2019; Accepted: 21 June 2019; Published: 25 June 2019

Abstract: The building sector accounts for one third of the global energy consumption and it is expected to grow in the next decades. This evidence leads researchers, engineers and architects to develop innovative technologies based on renewable energies and to enhance the thermal performance of building envelopes. In this context, the potential applicability and further energy performance analysis of these technologies when implemented into different building typologies and climate conditions are not easily comparable. Although massive information is available in data sources, the lack of standardized methods for data gathering and the non-public availability makes the comparative analyses more difficult. These facts limit the benchmarking of different building energy demand parameters such as space heating, cooling, air conditioning, domestic hot water, lighting and electric appliances. Therefore, the first objective of this study consists in providing a review about the common typologies of residential buildings in Europe from the main data sources. This study contains specific details on their architecture, building envelope, floor space and insulation properties. The second objective consists in performing a cross-country comparison in terms of energy demand for the applications with higher energy requirements in the residential building sector (heating and domestic hot water), as well as their related CO2 emissions. The approach of this comparative analysis is based on the residential building typology developed in TABULA/EPISCOPE projects. This comparative study provides a reference scenario in terms of energy demand and CO2 emissions for residential buildings and allows to evaluate the potential implementation of new supply energy technologies in hot, temperate and cold climate regions. From this study it was also concluded that there is a necessity of a free access database which could gather and classify reliable energy data in buildings.

Keywords: residential buildings; building energy demand; energy savings; building stock; cross-country comparison; TABULA; building stock observatory

1. Introduction

The reduction of energy consumption and the related CO2 emissions in the building sector are the main global environmental concerns in long-term perspective for sustainable development [1]. The building sector is the largest energy consumer in the world with approximately one third of

Energies 2019, 12, 2436; doi:10.3390/en12122436 www.mdpi.com/journal/energies Energies 2019, 12, 2436 2 of 17 the global final energy consumption and it is expected to grow closely with the increase of living standards [1,2]. This tendency is highly affected by the following key drivers that include the growth of the world population (41%), the increase in households that require energy (115%) and the increase in floor area per capita (50%) by 2050 [2]. Regarding these global energy trends in buildings, 24% of the global final energy demand comes from the residential sub-sector while the 8% remaining comes from commercial [2]. In addition, in developed countries, such as the European ones, the residential sector represents 41% of the final energy consumption and 40% of the total greenhouse gas (GHG) emissions [3]. In agreement with the European Union (EU) 2030 targets [4] in reducing the energy demand of buildings and preserving the environment through sustainable development, on one hand there are European renewable energy action plans [5] that encourage uptake active energy saving systems, such as renewable heating technologies. On the other hand, efficient building envelopes [6], building shape and orientation [7] are also promoted with the same aim, such as potential passive energy saving systems by international energy directives. Latest comprehensive literature reviews concerning both, European and global heating and cooling energy trends in buildings [2,8,9] pointed out the main key drivers that affect their final thermal energy use. The foremost in the residential sector are the number of households, person per household, floor space per capita and specific energy consumption for residential heating and cooling [2]. Only the last driver allows stakeholders (engineers, architects, building contractors, homeowners, etc.) to have a direct impact on reducing the energy demand of buildings. The EU building stock is very heterogeneous in terms of designs, construction systems, construction periods and equipped with a large variety of different heating and cooling systems [10,11]. Due to these facts there is still scarce and controversial information in the open source database that contains the characteristics of European building stock and their specific final energy consumption. In addition, there is a lack of studies that provide cross-country comparisons referring to the thermal properties of building envelopes, their energy demand and their CO2 emissions. Only one study carried out by Csoknyai et al. in 2016 [11] encompasses a similar comparative analysis for four Eastern countries: Bulgaria, Serbia, Hungary and the Czech Republic. These authors provided the total energy need for heating of the overall residential building stock by country, as well as the energy demand for heating and domestic hot water for the different building typologies. In their study, the building typologies were sorted by seven different building classes: three types of single family houses and four types of multi-flat buildings. All of them were grouped by the year of construction period in the following manner: before 1944, between 1945 and 1989 and after 1990. Moreover, the scarce and controversial information about the characteristics of the building stock in the EU and the lack of tools to evaluate their energy demands [12] represent a crucial limitation to evaluate the potential applicability of new and innovative technologies such as solar energy when implemented in real case scenarios. These technologies, which basically are based on renewable energy sources for heating, cooling and domestic hot water (DHW) in buildings, cannot be compared against conventional existing systems because of the missing benchmark scenario about the building characteristics and their energy demands. Frayssinet et al. (2018) [12] concluded in their study that there are still not entirely validated tools that are able to accurately and explicitly simulate the power demand of urban buildings at city scale. Since space heating and domestic hot water represent the major final energy consumption by households in Europe [2], specifically 79.2% [13], the importance of their reduction while maintaining indoor thermal comfort are key priorities in the future building scenario for promoting energy efficiency in the residential sector [14]. Thus, a free access data source that includes a building stock classification and allows the benchmarking in terms of energy demand for the defined building typologies and climate conditions must be created. This process should be carried out first at national and then at EU level to stablish a comparative framework in terms of quantitative values. In addition, free access data sources may help to improve the current limitations in the modelling of heat flow and the household Energies 2019, 12, 2436 3 of 17 behaviours, which are key parameters for policy makers in terms of investment decisions and energy using practices [15]. In this context, the first objective of this paper is to provide a study about the current classification of the building stock in Europe. The scope of the study will include information on types of residential buildings for Germany, France, UK, Italy, Spain and Sweden. The study will include the specific details on their architecture, building envelope, floor space and insulation properties. The second objective of this paper consists in performing a cross-country comparison in terms of energy demand, specifically for space and water heating that are the major energy consumer systems in the residential sub-sector [16]. The related CO2 emissions for the different building typologies in different climate conditions are also included in this study. This work establishes a base framework to be used in future studies to evaluate the potential applicability of new and innovative renewable technologies compared to the existing ones.

2. Materials and Methods All data used in this paper was obtained from three consecutive projects co-funded by the Intelligent Energy Europe Programme (IEE) [17], the new EU Building Stock Observatory [18] and the project Polices to Enforce the Transition to Nearly Zero Energy Buildings in the EU-27 (ENTRANZE) [19]. They include all the data regarding buildings from EU projects, national statistics, EPC databases, city sustainable energy action plans and industry data. All of these projects concentrate public information regarding the residential building stock characteristics at both, national and European levels.

2.1. IEE Project DATAMINE (2006–2008) This project aimed at improving the knowledge about the energy performance of building stocks forming a data structure for exchanging information. It intended to stimulate large-scale monitoring activities using energy performance certiﬁcates (approximately 19,000) as data source. All in all, the DATAMINE data structure is a suitable approach for the energy performance of buildings (EPBD) related data comparison and monitoring activities in the building sector on regional, national and European level, thus was successfully applied in 12 projects in 12 European countries.

2.2. IEE Project TABULA (2009–2012) The main goal of TABULA was to make an agreed systematic approach to classify building stocks according to their energy related properties. The core of this project was based on the DATAMINE structure. Within the TABULA project, residential building typologies have been defined for 20 European countries [20]. Each national typology consists of a classification grouping buildings according to their size, age and further technical construction parameters. Each typology is represented by a set of exemplary buildings per every national stock. This classification will also include the typical energy consumption for the given buildings, the showcase calculation of the possible energy savings and the common supply systems; regarding DHW, heating and cooling.

2.3. IEE Project EPISCOPE (2013–2016) This project takes building typologies defined into the TABULA project as a basis for building stock monitoring activities. The main project activity was to track the energy-related refurbishment progress of certain housing stock entirely and to extend the building typologies developed in TABULA project to further countries. Including a classification scheme, showcase example buildings, building stock and supply systems statistics. In addition, three different refurbishment levels were determined to evaluate information about the actual energy consumption of the considered housing stocks. Energies 2019, 12, x FOR PEER REVIEW 4 of 16

The interactive tool allows to establish online calculations displaying the energy related features and the potential energy savings by implementing passive and active refurbishment measures of the exemplary buildings from all EU countries. The main provided features are the following: • The EU residential building stock organized by type of building, size and age classes. • Technical data regarding the construction characteristics of the exemplary buildings such as the Energiesvisual2019, 12appearance, 2436 and the common construction elements (roof, walls, floors and windows)4 ofand 17 their thermal transmittances. • 2.4. TabulaTechnical WebTool data regarding the common heat supply systems and their energy performance indicators. • TheTypical main values outcome for the of theenergy three consumption aforementioned by energy projects carriers. founded by the IEE was a successfully database• Energy named saving TABULA measurements Web tool on [19 two] (Figure quality1), levels which (usual was created and advanced to share valuablerefurbishment information levels) withand the scientiﬁctheir impact community on the energy and building consumption. experts from European countries.

Figure 1. Figure 1. TABULATABULA WebTool database interfaceinterface [[21].21]. The interactive tool allows to establish online calculations displaying the energy related features Complete technical information related to the EU building stock characteristics and reliable data and the potential energy savings by implementing passive and active refurbishment measures of the on their energy related features are presented and evaluated in TABULA WebTool. However, the exemplary buildings from all EU countries. The main provided features are the following: calculation method is only focused on the energy use for space heating and domestic hot water of residentialThe EU buildings. residential Hence, building cooling, stock air organized conditioni byng, type lighting of building, and electric size and appliances age classes. are still not • consideredTechnical in this data tool regarding but canthe be easily construction added characteristicsin the future [22]. ofthe exemplary buildings such as the • visual appearance and the common construction elements (roof, walls, ﬂoors and windows) and 2.5. EUtheir Building thermal Stock transmittances. Observatory TechnicalSince the dataBuildings regarding Performance the common Institute heat supply Europe systems (BPIE) and [23] their closed energy the performance DATA HUB indicators. for the • energyTypical performance values for of thebuildings, energy all consumption data in the HU by energyB were transferred carriers. and updated to a new interface • (FigureEnergy 2) in savingthe European measurements Commission on two webpage quality [18]. levels (usual and advanced refurbishment levels) • andThis theirdata impactsource onwas the developed energy consumption. for the European Commission by BPIE in collaboration with Ecofys, ECN, Enerdata, Seven and many national partners. Besides providing and monitoring the energyComplete performance technical of informationthe building relatedstock characteristics to the EU building in Europe, stock characteristicsthe Observatory and assesses reliable dataimprovements on their energy in the relatedenergy featuresefficiency are levels presented in buildings and evaluated in EU countries. in TABULA Additionally, WebTool. However,it allows thenumerical calculation and visual method comparisons is only focused by using on the the energy massi useve database for space and heating the data and mapper domestic tools hot available water of residentialonline [18]. buildings.The new data Hence, base cooling, provides air an conditioning, easy comparison lighting among and electric many different appliances topics are still(items) not consideredsorted by countries in this tool and but years. can be Building easily added stock incharacteristics, the future [22 building]. shell performance, technical building systems, energy consumption and energy poverty, are some of them (Figure 2). Moreover,

Energies 2019, 12, 2436 5 of 17

2.5. EU Building Stock Observatory EnergiesSince 2019 the, 12, Buildings x FOR PEER PerformanceREVIEW Institute Europe (BPIE) [23] closed the DATA HUB5 forof 16 the energy performance of buildings, all data in the HUB were transferred and updated to a new interface it provides information regarding the available financing for building renovation and evaluates the (Figure2) in the European Commission webpage [18]. energy poverty levels across the EU28.

FigureFigure 2. 2.European European UnionUnion (EU)(EU) Building Stock Observatory Observatory database database interface interface [18]. [18 ].

ThisThe data main source advantage was developedof this database for the compared European to CommissionTABULA, is the by organization BPIE in collaboration by topics withor Ecofys,indicators ECN, (items Enerdata, tab in Seventhe left andmenu, many Figure national 2) and partners.the comprehensive Besides providingdata available. and Users monitoring can theeasily energy obtain performance an overall of idea the of building the energy stock tr characteristicsends, number of in dwellings Europe, the and Observatory so forth for assesses both improvementsresidential and in non-residential the energy effi buildings.ciency levels This in database buildings includes in EU additional countries. information Additionally, compared it allows numericalto TABULA and database visual comparisons such as the energy by using consumptio the massiven of database space cooling, and the cooking, data mapper lighting tools and availablewater onlineconsumption. [18]. The Nevertheless, new data base the providesObservatory an easyprovid comparisones rough numbers among that many makes diff erentmore difficult topics (items) the sortedcomparison by countries when approaches and years. for Building specific stock case stud characteristics,ies are planned. building The main shell drawbacks performance, are the technical lack of updated data (only available until 2014) and the missing information about some indicators such building systems, energy consumption and energy poverty, are some of them (Figure2). Moreover, as energy use per building, average values about the thermal transmittance of walls, floors, roofs, it provides information regarding the available financing for building renovation and evaluates the windows and so forth. This information is also missing for many EU countries (e.g. UK, France, Italy, energy poverty levels across the EU28. Germany, etc.). Finally, the last and more important drawback is that it is not possible to select The main advantage of this database compared to TABULA, is the organization by topics or different climate conditions within a country. indicators (items tab in the left menu, Figure2) and the comprehensive data available. Users can easily obtain3. Classification an overall ideaof the of Resi thedential energy Building trends, numberStock in ofEU dwellings and so forth for both residential and non-residential buildings. This database includes additional information compared to TABULA Valuable technical information about the benchmark of architecture of residential buildings and database such as the energy consumption of space cooling, cooking, lighting and water consumption. their energy requirements were obtained from the previously described databases. However, a Nevertheless, the Observatory provides rough numbers that makes more difficult the comparison standardized classification for the different residential building typologies is still not established and when approaches for specific case studies are planned. The main drawbacks are the lack of updated the literature shows a lack of standards for a cross-country comparison. data (only available until 2014) and the missing information about some indicators such as energy The scope of the study includes information on type of residential buildings in the five countries usethat per accounts building, for average 75% of values dwellings about in thethe thermalEU 27: Germany, transmittance France, of walls,UK, Italy floors, and roofs, Spain windows [9]. These and socountries forth. This are informationalso selected because is also missing they show for the many highest EU potential countries to (e.g. reduce UK, the France, energy Italy,consumption Germany, etc.).and Finally, CO2 emissions the last across and more the EU important [13]. Furthermore, drawback Sweden is thatit was is not also possible analysed to to select compare diff erentthe results climate conditionsof these countries within a against country. a country with very cold climate conditions. Within this context, Sousa et al. (2017) [15] divided the UK residential housing stock into five big groups: terraced (28%), bungalow (9%), semi-detached (26%), detached (17%) and apartments (20%). They used the traditional characterization of the building stock in UK that is organized into six age intervals: pre 1919, inter-war, post-war 1950s, industrial 1970s, modern 1980s and post 2000.

Energies 2019, 12, 2436 6 of 17

3. Classification of the Residential Building Stock in EU Valuable technical information about the benchmark of architecture of residential buildings and their energy requirements were obtained from the previously described databases. However, a standardized classification for the different residential building typologies is still not established and the literature shows a lack of standards for a cross-country comparison. The scope of the study includes information on type of residential buildings in the five countries that accounts for 75% of dwellings in the EU 27: Germany, France, UK, Italy and Spain [9]. These countries are also selected because they show the highest potential to reduce the energy consumption and CO2 emissions across the EU [13]. Furthermore, Sweden was also analysed to compare the results of these countries against a country with very cold climate conditions. Within this context, Sousa et al. (2017) [15] divided the UK residential housing stock into five big groups: terraced (28%), bungalow (9%), semi-detached (26%), detached (17%) and apartments (20%). They used the traditional characterization of the building stock in UK that is organized into six age Energies 2019, 12, x FOR PEER REVIEW 6 of 16 intervals: pre 1919, inter-war, post-war 1950s, industrial 1970s, modern 1980s and post 2000. Other data sources such as the EU Buildings Database [18] classifies the EU residential buildings Other data sources such as the EU Buildings Database [18] classifies the EU residential buildings into detached or semi-detached for single-family houses and only distinguishes one category for into detached or semi-detached for single-family houses and only distinguishes one category for multi-family houses, without any sub-category. Moreover, Theodoridou et al. [24] categorized the multi-family houses, without any sub-category. Moreover, Theodoridou et al. [24] categorized the residential building stock of Greece into six different classes (A, B1, B2, C, D and E) that encompasses residential building stock of Greece into six different classes (A, B1, B2, C, D and E) that encompasses parameters such as the year of construction, technical, political, social and historical activities. parameters such as the year of construction, technical, political, social and historical activities. This This classification was based on the analysis of statistical data provided by the Hellenic Statistical classification was based on the analysis of statistical data provided by the Hellenic Statistical Authority (EL. STAT.) which resulted in the division by typology and their year of construction. Authority (EL. STAT.) which resulted in the division by typology and their year of construction. It It highlighted the importance of age criterion since it can provide reliable information about the highlighted the importance of age criterion since it can provide reliable information about the building materials, typology and equipment directly related to the energy performance of the building. building materials, typology and equipment directly related to the energy performance of the The same authors stated in their research that similar residential building classification was performed building. The same authors stated in their research that similar residential building classification was in Germany, where eight different building types were used to represent the German stock. Similar performed in Germany, where eight different building types were used to represent the German cases were observed in Denmark, Italy and Switzerland. stock. Similar cases were observed in Denmark, Italy and Switzerland. With the same aim, the project TABULA divides the EU building stock into four main typologies With the same aim, the project TABULA divides the EU building stock into four main typologies (Figure3): single family house (SFH), terraced house (TH), multifamily house (MFH) and apartment (Figure 3): single family house (SFH), terraced house (TH), multifamily house (MFH) and apartment block (AB). Also, this database organizes the building stock by age and climate conditions from block (AB). Also, this database organizes the building stock by age and climate conditions from 20 20 different European countries to provide an easy cross-country comparison of building features, different European countries to provide an easy cross-country comparison of building features, measurements and energy performance [20]. measurements and energy performance [20].

Figure 3. Exemplary building typologies for for Spain from 2001 to 2016 divided in four typologies by TABULA WebToolWebTool [[21].21].

Single family houses can be generally characterised as one or two floors and single flat, detached or semi-detached house, while terraced houses are defined as attached one or two floors single flat. A multi-family house is a small building typified by a limited number of apartments (2 to 5 floors and up to 20 apartments) while apartment blocks are big buildings constituted by a large number of apartments that usually are composed of more than 4 floors and 15 apartments. The residential building classification proposed by TABULA is the most generic and reliable database because it allows the comparison of four different generic building typologies, two for single-family houses and two for multi-family houses. Additionally, each typology is subdivided in accordance with the age of construction (varies depending on the country) and two refurbishment levels. Moreover, the comprehensive building classification presented by TABULA is robust and includes the expertise of 15 EU different institutions that collaborated into the project development. They collected the information of residential buildings of 20 EU countries using the same TABULA concept. Finally, this approach was used to develop building stock models that enable the projection of the actual national building stock consumption and the energy saving potentials.

4. Main Parameters Considered for the Comparative Energy and CO2 Analysis The main technical parameters considered in this study are the thermal transmittance in steady state of the building envelopes (W/m2·K), the floor space (m2) and the annual energy demand for heating and domestic hot water (kWh/(m2·a)), which represents the largest energy consumption in residential sector. In addition to all of the aforementioned parameters, the CO2 emissions (kg) related to these demands will be presented.

Energies 2019, 12, 2436 7 of 17

Single family houses can be generally characterised as one or two floors and single flat, detached or semi-detached house, while terraced houses are defined as attached one or two floors single flat. A multi-family house is a small building typified by a limited number of apartments (2 to 5 floors and up to 20 apartments) while apartment blocks are big buildings constituted by a large number of apartments that usually are composed of more than 4 floors and 15 apartments. The residential building classification proposed by TABULA is the most generic and reliable database because it allows the comparison of four different generic building typologies, two for single-family houses and two for multi-family houses. Additionally, each typology is subdivided in accordance with the age of construction (varies depending on the country) and two refurbishment levels. Moreover, the comprehensive building classification presented by TABULA is robust and includes the expertise of 15 EU different institutions that collaborated into the project development. They collected the information of residential buildings of 20 EU countries using the same TABULA concept. Finally, this approach was used to develop building stock models that enable the projection of the actual national building stock consumption and the energy saving potentials.

4. Main Parameters Considered for the Comparative Energy and CO2 Analysis The main technical parameters considered in this study are the thermal transmittance in steady state of the building envelopes (W/m2 K), the ﬂoor space (m2) and the annual energy demand for · heating and domestic hot water (kWh/(m2 a)), which represents the largest energy consumption in · residential sector. In addition to all of the aforementioned parameters, the CO2 emissions (kg) related to these demands will be presented.

5. Results TABULA WebTool and Building Stock Observatory present information for different age groups for each country: six in Spain, twelve in Germany, ten in France, eight in Italy and eight in UK. Therefore, an overall building classification is selected to provide a comparative analysis of the energy demand and CO2 emissions of different types of residential building. In this paper, all age classes found in the literature were grouped into three different ones, namely from 1970 to 1985, from 1986 to 2000 and from 2001 to 2016. Moreover, due to the different climates per country, the climate conditions were divided into three different classes: hot, temperate and cold. These climate conditions were selected to obtain different energy requirements for each building typology thus providing up to 143 case scenarios.

5.1. Construction Characteristics of Building Models Notice that each building example presented in this study was based on the TABULA/EPISCOPE approach. Hence, they are the typical representative buildings that can be usually found in houses with similar age and size class. Since ﬂoor area per household (m2) is the conditioned ﬂoor area (CFA) based on internal dimensions (measured from edges at the inside surface of external walls), its dimensions are directly correlated with the construction period, the typology of the building and the country. As it can be seen in Figure4, single family and terraced houses were bigger in 1970–1985 when compared with those from 2001–2016 in Spain, Germany and France. However, the opposite trend is detected on multifamily houses and apartment blocks that are becoming more popular due to the room limitations in cities, the higher price of land and the rapid growth of urban environments. Figure4 highlights that multifamily houses and apartment blocks have a larger CFA in comparison to single family and terraced houses, especially in new apartment blocks in Spain that have 43 times larger CFA in comparison to single family houses and 53 times more compared to terraced houses. Energies 2019, 12, x FOR PEER REVIEW 7 of 16

5. Results TABULA WebTool and Building Stock Observatory present information for different age groups for each country: six in Spain, twelve in Germany, ten in France, eight in Italy and eight in UK. Therefore, an overall building classification is selected to provide a comparative analysis of the energy demand and CO2 emissions of different types of residential building. In this paper, all age classes found in the literature were grouped into three different ones, namely from 1970 to 1985, from 1986 to 2000 and from 2001 to 2016. Moreover, due to the different climates per country, the climate conditions were divided into three different classes: hot, temperate and cold. These climate conditions were selected to obtain different energy requirements for each building typology thus providing up to 143 case scenarios.

5.1. Construction Characteristics of Building Models Notice that each building example presented in this study was based on the TABULA/EPISCOPE approach. Hence, they are the typical representative buildings that can be usually found in houses with similar age and size class. Since floor area per household (m2) is the conditioned floor area (CFA) based on internal dimensions (measured from edges at the inside surface of external walls), its dimensions are directly correlated with the construction period, the typology of the building and the country. As it can be seen in Figure 4, single family and terraced houses were bigger in 1970–1985 when compared with those from 2001–2016 in Spain, Germany and France. However, the opposite trend is detected on multifamily houses and apartment blocks that are becoming more popular due to the room limitations in cities, the higher price of land and the rapid growth of urban environments. Figure 4 highlights that multifamily houses and apartment blocks have a larger CFA in comparison to single familyEnergies 2019and, 12terraced, 2436 houses, especially in new apartment blocks in Spain that have 43 times larger8 of 17 CFA in comparison to single family houses and 53 times more compared to terraced houses.

FigureFigure 4. 4. AverageAverage floor ﬂoor space space per per type type of of building building by by countries. countries.

TableTable 11 shows the representative thermal transmittancetransmittance valuesvalues ofof building envelope components suchsuch as as roofs, roofs, walls, ﬂoorsfloors and windowswindows forfor thethe modelmodel buildingsbuildings analysedanalysed in in this this paper. paper. It It provides provides a across-country cross-country comparison comparison in in terms terms ofof buildingbuilding envelopeenvelope performanceperformance and it also allows to to compare compare themthem according according to to the the type type of of building building through through the years. On one hand, the highest thermal transmittance of these construction components can be found in UK walls (1.60 W/m2 K) and Spanish roofs (4.17 W/m2 K) for single family houses (1970–1985). · · A substantial reduction of the thermal transmittance on those construction systems were achieved by 2001–2016 periods, where UK walls and Spanish roofs of single family houses are 0.35 W/m2 K · and 0.48 W/m2 K, respectively. These reductions can be attributed to the application of European and · national energy policies towards more eﬃcient buildings, which also had a direct impact on reducing the energy demand of buildings. On the other hand, the lowest thermal transmittance values for roofs and walls were detected in single family houses in Sweden, 0.21 W/m2 K and 0.13 W/m2 K, respectively. · · As expected, the coldest country have higher levels of insulation in the walls due to higher space heating demands. Energies 2019, 12, 2436 9 of 17

Table 1. Thermal transmittance values of the building envelope components (roof, walls, ﬂoors and windows) for the diﬀerent exemplary buildings (Single-family house, terraced house, multi-family house and apartment block) selected by country.

Thermal Transmittance of Roof, Walls, Floors and Windows, Respectively (W/m2 K) · Country Type of Building 1970–1985 1986–2000 2001–2016 Roof Wall Floor Window Roof Wall Floor Window Roof Wall Floor Window Single family house 4.17 1.33 0.85 4.59 0.61 0.60 0.85 3.09 0.48 0.48 1.31 3.09 Terrace house 1.67 1.33 0.85 5.70 1.92 0.72 1.31 3.09 0.42 0.48 0.44 2.92 Spain Multifamily house 1.61 1.64 0.71 5.70 0.56 0.56 1.39 - 0.45 0.52 0.56 3.37 Apartment block 1.92 1.33 1.13 5.70 1.61 0.60 1.31 3.37 0.48 0.48 0.71 3.37 Single family house 0.95 0.76 0.76 2.80 0.57 0.59 0.63 2.80 0.28 0.34 0.33 2.20 Terrace house 0.95 0.76 0.76 2.80 0.57 0.63 0.63 2.80 0.28 0.33 0.33 2.20 Italy Multifamily house 0.75 0.80 0.98 3.70 0.57 0.59 0.77 2.20 0.28 0.34 - 2.20 Apartment block 0.75 0.76 0.76 3.70 0.57 0.60 0.63 3.40 0.28 0.34 0.30 2.20 Single family house 0.49 0.61 0.40 2.80 0.22 0.36 0.42 2.60 0.18 0.33 0.31 1.80 Terrace house 0.43 0.61 0.90 3.10 0.22 0.36 0.42 1.80 0.18 0.33 0.32 1.60 France Multifamily house 0.43 0.61 1.25 2.80 0.38 0.33 0.36 2.60 0.28 0.33 0.36 1.60 Apartment block 0.76 0.79 0.40 2.80 0.43 0.36 0.37 3.30 0.28 0.33 0.31 1.60 Single family house 0.50 1.00 0.77 2.80 0.40 0.50 0.51 3.20 0.25 0.30 0.28 1.40 Terrace house 0.51 1.00 0.77 2.80 0.40 0.60 0.51 2.80 0.20 0.30 0.28 1.30 Germany Multifamily house 0.50 1.00 0.77 3.00 0.36 0.60 0.51 3.00 0.20 0.25 0.32 1.40 Apartment block 0.51 1.10 0.77 3.00 0.36 0.60 0.51 3.00 - - - - Single family house 1.50 1.60 0.59 4.80 0.35 1.60 0.40 3.10 0.20 0.35 0.23 1.85 Terrace house 1.50 1.60 0.50 3.10 0.35 1.60 0.40 3.10 0.20 0.35 0.23 1.85 UK Multifamily house 1.50 1.60 0.40 3.10 0.35 1.60 0.40 3.10 0.25 0.35 0.23 1.85 Apartment block 1.50 1.60 0.40 3.10 - - - - 0.25 0.28 0.23 1.85 Single family house 0.15 0.21 0.27 2.01 0.12 0.17 0.24 1.94 0.12 0.20 0.18 1.87 Sweden Multifamily house 0.17 0.33 0.27 2.04 0.15 0.22 0.24 1.80 0.13 0.21 0.24 1.97 Energies 2019, 12, x FOR PEER REVIEW 9 of 16

On one hand, the highest thermal transmittance of these construction components can be found in UK walls (1.60 W/m2·K) and Spanish roofs (4.17 W/m2·K) for single family houses (1970–1985). A substantial reduction of the thermal transmittance on those construction systems were achieved by 2001–2016 periods, where UK walls and Spanish roofs of single family houses are 0.35 W/m2·K and 0.48 W/m2·K, respectively. These reductions can be attributed to the application of European and national energy policies towards more efficient buildings, which also had a direct impact on reducing the energy demand of buildings. On the other hand, the lowest thermal transmittance values for roofs and walls were detected in single family houses in Sweden, 0.21 W/m2·K and 0.13 W/m2·K, respectively.Energies 2019, 12 ,As 2436 expected, the coldest country have higher levels of insulation in the walls due10 of to 17 higher space heating demands. 5.2. Energy Consumption for Heating and Domestic Hot Water 5.2. Energy Consumption for Heating and Domestic Hot Water Up to 14 climate conditions were analysed for the diﬀerent considered countries (Spain, France, Up to 14 climate conditions were analysed for the different considered countries (Spain, France, Italy, UK, Germany and Sweden). The total annual energy consumed for heating and domestic hot Italy, UK, Germany and Sweden). The total annual energy consumed for heating and domestic hot water of diﬀerent building typologies is given for hot, temperate and cold climate conditions of each water of different building typologies is given for hot, temperate and cold climate conditions of each analysed country (Table2). analysed country (Table 2). Table 2. Climate conditions of the analysed countries based on TABULA. Table 2. Climate conditions of the analysed countries based on TABULA. Selected Countries Type of Climate Selected Countries Type of Climate SpainSpain ItalyItaly FranceFrance GermanyGermany UKUK SwedenSweden TemperateTemperate climate climate AtlanticAtlantic MiddleMiddle H2H2 KasselKassel EnglandEngland ZoneZone IIII HotHot climate climate Mediterranean -- H3 H3 HamburgHamburg -- Zone Zone IIIIII ColdCold climate climate ContinentalContinental -- H1H1 GarmischGarmisch -- ZoneZone II BuildingBuilding type type SingleSingle family family house, house, terrace terrace house, house, multifamily multifamily house house and and apartment apartment block block

In southern countries such as Spain, Italy and some regions of France, with a predominant hot In southern countries such as Spain, Italy and some regions of France, with a predominant hot Mediterranean climate conditions the domestic hot water can account for more than a half of the total Mediterranean climate conditions the domestic hot water can account for more than a half of the total energy consumption of a building. As an example, a single family house in Spain (1986-2000) energy consumption of a building. As an example, a single family house in Spain (1986–2000) consumes consumes 48.1 kWh/m2·a to cover the heating and DHW demand (Figure 5), almost half of that energy 48.1 kWh/(m2 a) to cover the heating and DHW demand (Figure5), almost half of that energy demand demand comes· only from DHW requirements. However, in northern countries such as Germany or comes only from DHW requirements. However, in northern countries such as Germany or Sweden, Sweden, the energy consumption is higher for heating in comparison to the energy consumption for the energy consumption is higher for heating in comparison to the energy consumption for DHW. For a DHW. For a similar case scenario in Germany, the calculated delivered energy for heating & DHW similar case scenario in Germany, the calculated delivered energy for heating & DHW of a single family of a single family house, from 1986 to 2000, was 209.6 kWh/(m2·a) while only 10% of it were for DHW house, from 1986 to 2000, was 209.6 kWh/(m2 a) while only 10% of it were for DHW requirements. requirements. · Spain Italy France Germany UK Sweden 240 210 180 ·a] 2 150 120 90 60 30 0 andDHW [kWh/m Energy consumption for heating heating for consumption Energy 1970-1985 1986-2000 2001-2016 1970-1985 1986-2000 2001-2016 1970-1985 1986-2000 2001-2016 1970-1985 1986-2000 2001-2016 Single Family House Terraced House Multifamily House Apartment Block Types of buildings and periods FigureFigure 5. EnergyEnergy consumptionconsumption for for heating heating and and domestic domestic hot waterhot water in hot in climate hot climate conditions conditions by country. by country. DHW consumption is less dominant when compared over the total energy consumption of a

building in temperate or cold climate conditions. Figures6 and7 show the energy consumption for heating and domestic hot water for these climate conditions by country. Energies 2019, 12, x FOR PEER REVIEW 10 of 16 Energies 2019, 12, x FOR PEER REVIEW 10 of 16 DHW consumption is less dominant when compared over the total energy consumption of a buildingDHW in consumptiontemperate or coldis less climate dominant conditions. when compFiguresared 6 andover 7 theshow total the energy energy consumption consumption of for a heatingbuildingEnergies 2019 and in, 12 temperatedomestic, 2436 hotor coldwater climate for these conditions. climate conditions Figures 6 andby country. 7 show the energy consumption11 offor 17 heating and domestic hot water for these climate conditions by country.

Figure 6. Energy consumption for heating and domestic hot water in temperate climate conditions by Figure 6. Energy consumption for heating and domestic hot water in temperate climate conditions country.Figure 6. Energy consumption for heating and domestic hot water in temperate climate conditions by by country. country. Spain Italy France Germany UK Sweden 240 Spain Italy France Germany UK Sweden 210240 180210 ·a] 2 150180 ·a] 2 120150 12090 6090 3060 300

andDHW [kWh/m 0 andDHW [kWh/m Energy consumption for heating for consumptionEnergy 1970-1985 1986-2000 2001-2016 1970-1985 1986-2000 2001-2016 1970-1985 1986-2000 2001-2016 1970-1985 1986-2000 2001-2016 Energy consumption for heating for consumptionEnergy

Single1970-1985 Family1986-2000 House2001-2016 Terraced1970-1985 1986-2000 House2001-2016 Multifamily1970-1985 1986-2000 House2001-2016 Apartment1970-1985 1986-2000 Block2001-2016 Single Family House TerracedTypes ofHouse buildings Multifamily and periods House Apartment Block Types of buildings and periods Figure 7. Energy consumption for heating and domestic hot water in cold climate conditions by country. Figure 7. Energy consumption for heating and domestic hot water in cold climate conditions by country.FigureTABULA 7. Energy database consumption shows similar for heating energy and consumptiondomestic hot water for DHW in cold in climate all evaluated conditions European by countries;country. the range goes from the lowest case scenario, 7.8 kWh/(m2 a) in Sweden to the highest TABULA database shows similar energy consumption for DHW· in all evaluated European energy consumption case, 48.1 kWh/(m2 a) in Germany [19]. It was observed a difference of 40.3 countries;TABULA the range database goes fromshows the similar lowest energy case· scenario, consumption 7.8 kWh/m for 2DHW·a in Sweden in all toevaluated the highest European energy kWh/(m2 a) for DHW demand when different countries and climate conditions (hot, temperate and consumptioncountries;· the case,range 48.1 goes kWh/m from the2·a inlowest Germany case scenario, [19]. It was 7.8 observed kWh/m2·a a indifference Sweden toof the40.3 highest kWh/m energy2·a for cold) were compared. However, after having analysed Figures5–7, the comparison was conducted for DHWconsumption demand case, when 48.1 different kWh/m2 ·acountries in Germany and [19]. climat It wase conditions observed (hot,a difference temperate of 40.3 and kWh/m cold) 2·awere for the energy consumption for heating at the same climate conditions, the maximum difference was about compared.DHW demand However, when afterdifferent having countries analysed and Figures climat e5–7, conditions the comparison (hot, temperate was conducted and cold) for were the 197 kWh/(m2 a). Therefore, the energy consumption of DHW could be related to the performance of energycompared. consumption However,· for after heating having at theanalysed same climate Figures conditions, 5–7, the comparison the maximum was difference conducted was for about the the energy equipment but especially to the human behaviour, meanwhile the energy consumption for 197energy kWh/(m consumption2·a). Therefore, for heating the energy at the consumptionsame climate ofconditions, DHW could the bemaximum related to difference the performance was about of heating is mainly attributed to the regional climate conditions and the building insulation level. 197 kWh/(m2·a). Therefore, the energy consumption of DHW could be related to the performance of Moreover, Figures5–7 show that the energy consumption for heating and DHW is lower in

apartment blocks in comparison to single family houses for all the EU countries analysed. These results

point out the importance of the building shape, as higher compactness in apartment blocks and Energies 2019, 12, 2436 12 of 17 multifamily houses results in less energy consumption per square meter per year for heating. These results are in agreement with those obtained in the energy benchmarking for residential buildings performed by Tereci et al. (2013) [25] in heating dominant climates. The building shape can reduce the heating demand up to 35%. In addition, they concluded that compact multi-family houses have the lowest energy demand and CO2 emissions while old apartments with courtyard showed the highest heating demand. Many variations in energy consumption were observed for the same building typology when countries and building construction periods are compared. As an example, regarding the standard thermal transmittance (Table1) for walls of a single family house; in Germany (2001–2016) is 0.30 W /m2 K · while in Spain for the same building characteristics and period is 37.5% higher (0.48 W/m2 K). However, · a German single family house in a temperate climate demands 59% more energy (76.8 kWh/(m2 a)) · only for heating in comparison to the same building typology in Spain, that requires 31.8 kWh/(m2 a). · Thus, buildings in northern countries such as the UK, Germany and Sweden have higher heating energy demands, even though they are better insulated, in comparison to southern countries such Spain, France and Italy. This fact is directly related to the climate conditions. Finally, as expected, the energy consumption for water and space heating of a speciﬁc building increases according to the climate conditions, being the hot climate the lowest and the cold one the highest energy requirements. So, the same building typology, requires more energy demand for heating and DHW in cold than in hot climate conditions.

5.3. Comparative Analysis of CO2 Emissions

The current state of CO2 emissions for residential buildings is presented in this section. The analysis included the CO2 emissions related to the energy consumption for heating and domestic hot water systems. To have a more realistic approach, the emissions due to the electricity consumption by electrical appliances and lighting per household are also considered (Table3). In order to calculate the CO2 emissions as a result of the electricity consumption for non-heating purposes, the standard CO2 emission factor for the power production was applied for each country [26].

Table 3. Average of electricity consumption for electrical appliances and lighting per electriﬁed household (kWh/(m2 a)) [27]. · Years Countries 2000 2005 2010 2011 2012 2013 2014 Electricity Consumption (kWh/(m2 a)) · France 25.66 28.38 29.88 29.68 29.88 29.76 29.90 Germany 22.93 23.61 26.19 24.92 25.30 25.50 25.73 Italy 18.86 17.35 16.11 16.03 15.53 14.79 14.49 Spain 21.66 23.30 24.34 25.68 25.03 23.88 24.10 Sweden 57.44 59.00 63.30 58.91 60.40 58.46 58.54 UK 43.47 47.80 41.77 41.72 40.39 39.39 38.28

In addition to the electrical energy consumption for electrical appliances and lighting, the average size of dwelling (Table4) was established based on the project ENTRANZE [19]. Figure8 shows the estimated electrical energy consumption for lighting and appliances per square metre at the European model buildings studied in this paper. Sweden shows the highest electrical energy consumption levels of around 60 kWh/(m2 a), followed by UK with the average value of · 40 kWh/(m2 a) (from 2010 to 2014). Spain, Germany and France have similar electrical consumption · rates, namely over 24, 25 and 30 kWh/(m2 a), respectively. Italy has the lower value, which decreased · from 19 kWh/(m2 a) in 2000 to 14 kWh/(m2 a) in 2014 (Figure8). · · EnergiesEnergies2019 2019, ,12 12,, 2436 x FOR PEER REVIEW 1213 ofof 1716

Table 4. Average size of dwellings (m2 per dwelling). Table 4. Average size of dwellings (m2 per dwelling). Country Source Average Floor Area (m2) Country Source Average Floor Area (m2) France ODYSSEE 92 GermanyFrance ODYSSEEIWU 9284 Germany IWU 84 Italy ODYSSEE, TABULA, ISTAT 96 Italy ODYSSEE, TABULA, ISTAT 96 SpainSpain TABULA,TABULA, ODYSSEE ODYSSEE 94 94 SwedenSweden ODYSSEEODYSSEE 9191 UKUK RES-H,RES-H, ODYSSEE ODYSSEE 75 75

FigureFigure 8.8. Estimation ofof the electrical energy consumptionconsumption forfor appliancesappliances andand lightinglighting perper squaresquare metremetre byby country.country.

The total CO2 emissions due to energy consumption in residential buildings under hot, temperate The total CO2 emissions due to energy consumption in residential buildings under hot, and cold climate conditions, which includes heating, DHW and electricity, can be seen in Figures9–11. temperate and cold climate conditions, which includes heating, DHW and electricity, can be seen in 2 The CO2 emissions per square metre range from 113.4 kgCO2eq/(m a) for an old British multifamily Figures 9–11. The CO2 emissions per square metre range from 113.4 kgCO2eq/(m2·a) for an old British 2 · house (1970–1985) in a cold climate (Figure 11) to 11.5 kgCO2eq/(m a) for a terraced house (1986–2000) multifamily house (1970–1985) in a cold climate (Figure 11) to 11.5· kgCO2eq/(m2·a) for a terraced in hot French climate conditions (Figure9). house (1986–2000) in hot French climate conditions (Figure 9). When comparing results for CO2 emissions against the energy consumption (see Figures5–7 When comparing results for CO2 emissions against the energy consumption (see Figures 5–7 for forheating heating and and DHW DHW and andFigure Figure 8 for8 the for estimation the estimation of the of electrical the electrical energy energy consumption) consumption) the effect the of etheffect technology of the technology used to usedprovide to providethe heating the heatingenergy can energy be clearly can be seen. clearly Therefore, seen. Therefore, despite despiteSweden Sweden being a higher energy consumer than UK, Sweden emits less CO2 than the UK (Figures9–11). being a higher energy consumer than UK, Sweden emits less CO2 than the UK (Figures 9–11). In InSweden, Sweden, district district heating heating based based on on biomass biomass and and wast wastee supplies supplies more more than than the 40% of the heatheat demanddemand inin buildingsbuildings [[28].28]. ForFor thethe samesame reason,reason, nuclearnuclear powerpower plantsplants havehave similarsimilar eeffectsffects onon thethe electricityelectricity production.production. So, despitedespite thethe factfact thatthat FranceFrance consumesconsumes moremore electricityelectricity (Figure(Figure8 )8) in in comparison comparison to to Italy or Spain, CO2 emissions levels in France are lower than its neighbouring countries due to a high Italy or Spain, CO2 emissions levels in France are lower than its neighbouring countries due to a high nuclearnuclear portionportion inin thethe FrenchFrench energyenergy mixmix [[29].29]. Spain,Spain, Germany,Germany, ItalyItaly andand UKUK mainmain fuelfuel sourcessources forfor heatingheating purposespurposes areare fossilfossil fuelsfuels andand electricityelectricity [[21]21] butbut unlikeunlike FranceFrance theirtheir electricityelectricity waswas alsoalso mainlymainly produced by fossil fuels at the time used for this study [29]. Hence, their CO2 emissions are directly produced by fossil fuels at the time used for this study [29]. Hence, their CO2 emissions are directly relatedrelated with with their their energy energy consumption. consumption. Moreover, Moreover, the the decrement decrement trends trends observed observed over over the yearsthe years in the in energy consumption in Figures5–7 are also detected in the CO 2 emissions for the different building the energy consumption in Figures 5–7 are also detected in the CO2 emissions for the different typologiesbuilding typologies in all countries in all countries (Figures9 –(Figures11). 9–11).

Energies 2019, 12, x FOR PEER REVIEW 13 of 16 Energies 2019, 12, 2436 14 of 17 EnergiesSpain Electricity 2019, 12, x FORItaly PEER Electricity REVIEW France Electricity Germany Electricity UK Electricity Sweden Electricity13 of 16 Spain Heating&DHW Italy Heating&DHW France Heating&DHW Germany Heating&DHW UK Heating&DHW Sweden Heating&DHW Spain120 Electricity Italy Electricity France Electricity Germany Electricity UK Electricity Sweden Electricity Spain110 Heating&DHW Italy Heating&DHW France Heating&DHW Germany Heating&DHW UK Heating&DHW Sweden Heating&DHW 120 100 110 90 100 .a)]

2 80 90 70 .a)]

2 80 eq/(m

2 60 70 50 eq/(m

2 60 40 50 30 40 20

emissions [kgCO emissions 30 2 10 20 CO emissions [kgCO emissions 0 2 10 1970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-2016 CO 0 Single Family House Terraced House Multifamily House Apartment Block 1970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-2016 Type of Building and periods Single Family House Terraced House Multifamily House Apartment Block Figure 9. CO2 emissions of electricity, Typeheating of Buildingand DHW and consumption periods per square metre in hot climates. FigureFigure 9. 9.CO CO2 emissions2 emissions of electricity,of electricity, heating heating and and DHW DHW consumption consumption per squareper square metre metre in hot in climates. hot

Spainclimates. Electricity Italy Electricity France Electricity Germany Electricity UK Electricity Sweden Electricity Spain Heating&DHW Italy Heating&DHW France Heating&DHW Germany Heating&DHW UK Heating&DHW Sweden Heating&DHW Spain120 Electricity Italy Electricity France Electricity Germany Electricity UK Electricity Sweden Electricity Spain110 Heating&DHW Italy Heating&DHW France Heating&DHW Germany Heating&DHW UK Heating&DHW Sweden Heating&DHW 120 100 110 90 100 .a)] 2 80 90

.a)] 70 2

eq/(m 80 2 60 70 eq/(m

2 50 60 40 50 30 40

emissions [kgCO 20

2 30 10 CO

emissions [kgCO 20 2 0 10 CO 1970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-2016 0 Single Family House Terraced House Multifamily House Apartment Block 1970-19851986-20002001-20161970-19851986-20002001-20161970-1985Type of Building and periods1986-20002001-20161970-19851986-20002001-2016 Single Family House Terraced House Multifamily House Apartment Block Figure 10. CO emissions of electricity, heating and DHW consumption per square metre in Figure 10. CO2 2emissions of electricity, heatingType and of Building DHW consumption and periods per square metre in temperate temperateclimates. climates. Figure 10. CO2 emissions of electricity, heating and DHW consumption per square metre in temperate

Referringclimates.Referring to to thethe CO2 emissions,emissions, it itcan can be benoticed noticed that thatthe difference the diﬀerence between between temperate temperate and cold and coldclimate climate locations locations is not is relevant not relevant in all in the all analysed the analysed countries countries except exceptfor all building for all building typologies typologies from from1970–1985 1970–1985Referring periods periodsto the in CO Spain in2 emissions, Spain and and France it France can (Figuresbe (Figuresnoticed 10 that 10and and th 11).e difference11 These). These buildings between buildings temperateshowed showed important and important cold climate locations is not relevant in all the analysed countries except for all building typologies from incrementsincrements of of the the CO CO2 2emissions emissions becausebecause of the low low building building insulation insulation levels levels in inthis this period period and and the the 1970–1985 periods in Spain and France (Figures 10 and 11). These buildings showed important bigbig temperature temperature variations variations betweenbetween coldcold and hot climate climate conditions conditions in in southern southern European European regions regions increments of the CO2 emissions because of the low building insulation levels in this period and the (Spain,(Spain, Italy Italy and and France) France) when when compared compared to the to samethe same variations variations in northern in northern countries countries such as such Germany, as big temperature variations between cold and hot climate conditions in southern European regions UKGermany, and Sweden. UK and Sweden. (Spain, Italy and France) when compared to the same variations in northern countries such as Germany, UK and Sweden.

Energies 2019, 12, 2436 15 of 17 Energies 2019, 12, x FOR PEER REVIEW 14 of 16

Spain Electricity Italy Electricity France Electricity Germany Electricity UK Electricity Sweden Electricity Spain Heating&DHW Italy Heating&DHW France Heating&DHW Germany Heating&DHW UK Heating&DHW Sweden Heating&DHW 120 110 100 90 .a)] 2 80 70 eq/(m 2 60 50 40 30 20 emissions [kgCO emissions 2 10 CO 0 1970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-20161970-19851986-20002001-2016 Single Family House Terraced House Multifamily House Apartment Block Type of Building and periods Figure 11. Figure 11.CO CO2 emissions2 emissions of electricity,heatingof electricity, heating and DHWand DHW consumption consumption per square per square metre metre in cold in climates. cold climates. 6. Conclusions

6. ConclusionsThis study provides a comprehensive benchmarking of the energy demand and the CO2 emissions in the EU residential buildings. The study includes data from six different countries which account for This study provides a comprehensive benchmarking of the energy demand and the CO2 threeemissions quarters in ofthe the EU total residential dwellings buildings. in Europe. The study includes data from six different countries which accountThe main for three outcome quarters of theof the study total is dwellings that there in is Europe. a necessity of a free access database that gathers standardizedThe main data outcome of the of building the study stock. is that So, there a reliable is a necessity and comparable of a free access data database regarding that the gathers energy aspectsstandardized in buildings data canof the be ensuredbuilding andstock. accessed. So, a reliable This willand allowcomparable to address data theregarding current the limitation energy in thisaspects sector. in buildings can be ensured and accessed. This will allow to address the current limitation in thisNowadays, sector. there is a controversy regarding the classification of the residential building stock. After aNowadays, literature review, there is the a controversy most interesting regarding building the classification classification of is the the residential one provided building by TABULAs stock. project.After a Itliterature is a robust review, and the contrasted most interesting free access buildi datang classification source based is the on one three provided consecutive by TABULAs projects. However,project. theIt is energya robust consumption and contrasted for cooling,free access air data conditioning, source based lighting on three and consecutive electric appliances projects. are notHowever, already consideredthe energy consumption in this database. for cooling, The Europeanair conditioning, Building lighting Stock and Observatory electric appliances is also aare free accessnot already database considered that considered in this database. those data The but European presents Building some important Stock Observatory drawbacks is thatalso limita free the comparativeaccess database analysis. that considered those data but presents some important drawbacks that limit the comparative analysis. The EU building stock is very heterogeneous, and its energy demand varies depending on the The EU building stock is very heterogeneous, and its energy demand varies depending on the following principal factors: climate conditions, insulation level and the type of building among others. following principal factors: climate conditions, insulation level and the type of building among The energy consumed for space and water heating of the evaluated can differ in 197.4 kWh/(m2 a). others. The energy consumed for space and water heating of the evaluated can differ in 197.4· This fact shows that a proper evaluation of the energy demand in the building sector can help to assess kWh/(m2·a). This fact shows that a proper evaluation of the energy demand in the building sector can new the installation of new and innovative technologies. The principal parameters that affect the help to assess new the installation of new and innovative technologies. The principal parameters that finalaffect energy the final demand energy of demand all Spanish of all building Spanish stockbuildi withinng stock the within 1970–1985 the 1970–1985 period period are: first are: the first climate the conditions,climate conditions, second the second insulation the insulation level, and, level, finally and, the finally building the building shape. However,shape. However, since generally since thegenerally level of insulationthe level of in insulation Germany, Swedenin Germany, and UKSweden countries and UK is very countries high, climateis very conditionshigh, climate have hadconditions less relevance have had on less the relevance variation on of the variation building of energy the building the heating energy requirements the heating requirements of a building areof mainly a building attributed are mainly to the attributed climate conditions,to the climate type conditions, of building type and of thebuilding building and insulation the building level. Whileinsulation the domestic level. hotWhile water the demanddomestic is hot related water to thedemand human is habitsrelated and to thethe performancehuman habits of theand overall the supplyperformance system. of the overall supply system. ResultsResults lead lead the the authors authors to to concludeconclude thatthat DHW plays an an important important role role on on the the total total building building energyenergy demand demand in in the the hot hot Mediterranean Mediterranean climateclimate inin Spain and France. France. DHW DHW consumes consumes up up to to50% 50% of of

Energies 2019, 12, 2436 16 of 17 the energy consumed for the specific buildings in the period 2001–2016 of those countries. However, in cold climatic conditions, in Germany or Sweden, DHW did not reach 10% of the energy consumed. This paper provides a reference scenario of the energy demand and CO2 emissions from different building stocks. This reference can be used in further investigations to evaluate the potential applicability of new HVAC and DHW technologies and compare them to the current ones. Further research should focus on analysing the role of human behaviour in the final energy demand of a building, as well as the energy consumption for cooling, lighting and appliances. In addition, the energy demand of non-residential buildings is becoming increasingly important that is why future studies should focus also on this topic.

Author Contributions: L.F.C. and A.d.G. conceived and designed the study to be performed; J.C., J.M.M., T.B. and T.G. performed the data searching process; J.C. and J.M.M. analysed the data; J.C. and J.M.M. wrote the paper. All authors contributed to discuss the obtained results. The article was reviewed by every single co-author. Funding: This study has received funding from European Union’s Horizon 2020 research and innovation programme under grant agreement Nº723596 (Innova MicroSolar). The work is partially funded by the Spanish government (RTI2018-093849-B-C31). Julià Coma would like to thank Ministerio de Economía y Competitividad de España for Grant Juan de la Cierva, FJCI-2016-30345. José Miguel Maldonado would like to thank the Spanish Government for his research fellowship (BES-2016-076554). This work is partially supported by ICREA under the ICREA Academia programme. Acknowledgments: GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). Conflicts of Interest: The authors declare no conflict of interest.

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