European residential buildings and empirical ...

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Building and Environment 42 (2007) 1298–1314 www.elsevier.com/locate/buildenv

European residential buildings and empirical assessment of the Hellenic building stock, energy consumption, emissions and potential energy savings Constantinos A. Balarasa,, Athina G. Gagliaa, Elena Georgopouloub, Sevastianos Mirasgedisb, Yiannis Sarafidisb, Dimitris P. Lalasb a

Group Energy Conservation, Institute for Environmental Research & Sustainable Development, National Observatory of Athens, I. Metaxa & Vas. Pavlou, GR 15236 P. Penteli, Greece b Group Energy Planning and Sustainable Development, Institute for Environmental Research & Sustainable Development, National Observatory of Athens, I. Metaxa & Vas. Pavlou, GR 15236 P. Penteli, Greece Received 12 April 2005; accepted 25 August 2005

Abstract The existing building stock in European countries accounts for over 40% of final energy consumption in the European Union (EU) member states, of which residential use represents 63% of total energy consumption in the buildings sector. Consequently, an increase of building energy performance can constitute an important instrument in the efforts to alleviate the EU energy import dependency (currently at about 48%) and comply with the Kyoto Protocol to reduce carbon dioxide emissions. This is also in accordance to the European Directive (EPBD 2002/91/EC) on the energy performance of buildings, which is currently under consideration in all EU member states. This paper presents an overview of the EU residential building stock and focuses on the Hellenic buildings. It elaborates the methodology used to determine the priorities for energy conservation measures (ECMs) in Hellenic residential buildings to reduce the environmental impact from CO2 emissions, through the implementation of a realistic and effective national action plan. A major obstacle that had to overcome was the need to make suitable assumptions for missing detailed primary data. Accordingly, a qualitative and quantitative assessment of scattered national data resulted to a realistic assessment of the existing residential building stock and energy consumption. This is the first time that this kind of aggregate data is presented on a national level. Different energy conservation scenarios and their impact on the reduction of CO2 emissions were evaluated. Accordingly, the most effective ECMs are the insulation of external walls (33–60% energy savings), weather proofing of openings (16–21%), the installation of double-glazed windows (14–20%), the regular maintenance of central heating boilers (10–12%), and the installation of solar collectors for sanitary hot water production (50–80%). r 2005 Elsevier Ltd. All rights reserved. Keywords: Building stock; Energy consumption; Conservation; Performance; CO2 emissions

1. Introduction The European Union (EU) Member States are working intensively to improve energy efficiency in all end-use sectors and to increase the exploitation of renewable energy sources (RES) in order to tackle environmental concerns deriving from energy consumption of fossil fuels, and to support self-sufficiency and energy security. Energy effiCorresponding author. Tel.: +30 210 8109152; fax: +30 210 8103236.

E-mail address: [email protected] (C.A. Balaras). 0360-1323/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.buildenv.2005.11.001

ciency is expected to play a key role in meeting the EU target in accordance to the Kyoto commitments to reduce CO2 emissions in an economic way. In 2002, the gross inland consumption in the EU-25 member states was 1677 Mtoe [1]. The final energy consumption reached 1080 Mtoe, of which 44% oil, 23.9% gas, 20.2% electricity, 4.8% solid fuels, 4.2% renewables and 2.8% derived heat. This is a grim situation given that the EU-25 import dependency is 48% for all fuels, and 76.8% for oil, 51.3% for gas and 33.2% for solid fuels. The European Commission estimates that the import

ARTICLE IN PRESS C.A. Balaras et al. / Building and Environment 42 (2007) 1298–1314

dependency will reach two-thirds by 2020 [2], with increased risks for the energy security of supply, unless some urgent additional measures and policies are adopted. Since 1990, the implemented energy efficiency policies and measures in the EU-15 contributed to an overall 10%, or 1% per annum (pa), improvement of the energy efficiency between 1990 and 1998 [3]. Industry has been the most important contributor to this success, achieving an annual energy efficiency gain of 1.8% pa between 1990 and 2001; thus, in 2001 industry is almost 25% more efficient than in 1990. Transport and households, have exhibited a modest improvement, reaching 6% and 5%, respectively. Since 1998, there is no more progress in these two sectors. Buildings are also a major pollution source. The most important greenhouse gas (GHG) by far is carbon dioxide (CO2), accounting for 82% of total EU emissions in 2002. About 39% of total EU emissions of CO2 originate from electricity and heat production. In addition, CO2 emissions from residential buildings are the fourth largest key source of GHG emissions in the EU and account for 10% of total GHG emissions in 2002, while emissions from commercial buildings are ranked fifth and account for 3.7% of the total [4]. However, considering the aggregate electrical and thermal energy consumption, buildings account for about a third of the total energy related CO2 emissions, and even higher in some countries depending on the use of electrical energy and fuel used for power production [5]. Significant potential exists to reduce the rate of future emissions in the building sector by promoting more rapid uptake of energy efficiency in buildings [6]. On average, between 1980 and 1990, CO2 emissions from buildings have grown by 1.7% pa with growth rates about four times greater in developing countries. Aggressive implementation of energy-efficient technologies and measures can lead to a reduction in CO2 emissions from residential buildings in 2010 by 1190 Mt CO2 pa in developed countries at costs ranging from US$68 to US$41/tCO2 avoided, and by 459 MtCO2 pa in developing countries at costs of US$68 to US$14/tCO2 avoided [5]. Another major environmental impact of buildings is the production of construction wastes that have a major impact on landfills. According to the European Environment Agency, construction and demolition (C&D) waste accounts for 10–33% of the total waste streams, demolition waste comprises 40–50% of the total C&D waste, renovation waste 30–50% and construction waste 10–20%. Given the low turn-over rate of buildings (lifetime of 50 to more than 100 years) and the high number of existing buildings, it is clear that the largest potential for improving energy performance in the short and medium term is in the existing stock of buildings. This can also have a significant impact on the efforts to reduce GHG emissions in accordance to the Kyoto protocol that came into effect on 16 February 2004 and the ratified commitments by most EU member states, which call for an overall 8% reduction in the EU compared with 1990 values, by 2012. Building refurbishment should also be viewed as an opportunity to

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exploit renewable energy sources and related technologies, with an emphasis on passive and active solar energy solutions, daylighting, natural cooling, cogeneration of heat and power, connection to district heating/cooling, which are becoming a part of national strategic policies. The recent EU Directive (EPBD) on the energy performance of buildings [7] mandates that by the end of 2005 all EU member states bring into force national laws, regulations and administrative provisions for setting minimum requirements on the energy performance of new and existing buildings that are subject to major renovations, and for energy performance certification of buildings. Additional requirements include regular inspection of building systems and installations, an assessment of the existing facilities and to provide advice on possible improvements and on alternative solutions. All member states are now developing schemes in response to the EPBD, although some have progressed more than others [3,8–11]. However, there are concerns that the EPBD does not properly address the serious problems for existing residential buildings. For example, the EPBD currently refers to buildings with a useful floor area greater than 1000 m2, which may be more suitable for tertiary sector buildings [9,12]. This limit will probably be lower in most national regulations, to include buildings with a lower value of the total useful floor area, like houses, residential buildings with a few dwellings, and other smaller size buildings in the tertiary sector. Ideally, including the entire building stock would result to the greatest energy and CO2 emission savings. The work reported in this paper was performed in the framework of a national project initiated by the Hellenic Ministry for the Environment Physical Planning and Public Works (MEPPPW), to quantify the potential benefits and to determine the priorities of building energy conservation strategies to reduce CO2 emissions. The main goals were to: collect and adapt available data for the existing building stock and energy consumption; estimate the normalized thermal and electrical energy consumption for heating, cooling, lighting breakdown, for existing buildings and predict growth for new buildings; estimate energy savings from: thermal insulation, double glazing, weather proofing (sealing) of openings to reduce infiltration, new boilers, maintenance, solar protection, energy efficient lamps, solar collectors, HVAC, automatic controls, etc., for residential and tertiary sector buildings, at different climatic zones; estimate the cost of ECMs; propose supporting policies for an implementation plan, including laws, regulations, administrative provisions, and financing, thus formulating a sound basis for the selection of specific policies that can minimize the financial impact and maximize the social welfare. Suitable supporting policies for the promotion of specific energy conservation interventions in the buildings sector were identified and proposed, based on the results of this study. Parallel actions included an evaluation of existing and under development national regulations on the rational use and energy conservation in buildings, and

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C.A. Balaras et al. / Building and Environment 42 (2007) 1298–1314

the development of an action plan. The greatest obstacle encountered during this work was the lack of detailed data for the existing building stock and its characteristics, and actual energy consumption. However, the overall approach may be applicable to other countries facing similar problems. 2. European buildings The number of dwellings in EU-25 are about 196 million [13], of which about 80% is concentrated in five countries: Germany (18.6%), Italy (13.8%), UK (13.2%), France (12.7%), Spain (10.8%), Poland (6.5%) and The Netherlands (3.5%). The annual rate of construction of new dwellings expressed as a percentage of the size of existing stock ranges from 0.3% in Sweden to 3.5% in Ireland with an average of 1.1%, while the estimated annual replacement rate (ratio of the annual demolition rate to the size of existing stock) for dwellings in Europe is actually very low, only 0.07% [9]. However, growth in European construction will begin to slow down, with new housing construction expected to be +0.7% in 2005 compared to +4.4% in 2004 [14]. Furthermore, the emphasis is expected to shift towards repair and maintenance of the existing housing stock in western Europe, while in the developing markets of eastern Europe is expected to accelerate sharply. 2.1. Energy consumption During the period of 1990–2000, the number of European dwellings increased by 0.9% pa, while the energy demand was limited to 0.4% pa [15]. This was mainly the result of better building design, materials, construction, and more efficient equipment, which are progressively being introduced to the market, and the restructuring of the new EU member states economies involving a more rational use of energy as a result of increasing fuel prices. On the other hand, it is not always possible to secure the desirable indoor conditions in existing, usually inefficient, older buildings due to high-energy costs and lower financial resources of their occupants. European households spent one fifth of their expenditure on housing, water, and energy linked to housing (21%), which is by far the biggest share when compared with other consumption purposes [16]. In 2001, it ranged from 29% in Sweden to below 10% in Cyprus and Malta, differences that are probably influenced by energy related expenses. A cross-country analysis of housing conditions, energy-efficiency levels, affordability and satisfaction with housing in 14 European countries using data from the European Statistical Office’s European Community Household Panel (ECHP), revealed that the households which declare an inability to adequately heat their home averages 17% for the EU-15, but only 4% in northern Europe [17]. Southern European countries may be considered as fuel-poor, which is a classic qualitative definition of fuel poverty, with an alarming 45% of

households in Greece, 55% in Spain and 74% in Portugal declare this inability. According to the European Commission, D.G. for Energy and Transport, the residential energy use per capita (cap) varies widely among European countries, for example, from 1500–5000 kWh/cap in southern Europe (i.e. Portugal, Spain and Greece), 6000–8000 kWh/cap in most of northwest Europe, to over 8000 kWh/cap in Scandinavian countries [1]. Levels in most EU countries are fairly steady, fluctuating from year to year with the weather, but in some southern European countries, like Greece and Spain, residential energy use increased steadily during the last decade. The average consumption of electricity per capita in the residential sector is also quite diverse, depending on the level of diffusion of electrical appliances and the use of electric space heating [8], ranging from 1000 (i.e., Portugal, Italy) to around 2000 kWh/cap (i.e., UK, France) and even upto 4500 kWh/cap in some countries (i.e., Sweden). A similar trend is observed for the household energy use per person, according to the International Energy Agency, starting for southern European countries from 3370 kWh/person in Portugal, 3600 kWh/person in Spain and reaching 11,400 kWh/ person in Finland and 17,700 kWh/person in Luxembourg, which are comparable with 10,350 kWh/person in USA and 11,160 kWh/person in Canada. Total energy demand of dwellings is expected to increase by 0.6% pa in 2000–2030 [15]. Given limited population growth, this is mainly due to the rising number of dwellings (+40 million between 2000 and 2030, with 0.68% pa in EU-25), resulting from changes in age structure, lifestyles and dwellings size. The EU final energy consumption for 2002 in the buildings sector amounted to 435 Mtoe (40.3% of the total EU-25 final energy use), of which 274 Mtoe in dwellings (25.4%). The member states with the highest final energy consumption in the residential and tertiary sector (Fig. 1) is Germany, United Kingdom, France and Italy [1]. In terms of the percentage of buildings’ final energy consumption to the total energy consumption (% buildings/total) the values occur in the new member states, including Latvia (56.9% of the total), Hungary (56.1%), Estonia (53.5%), Poland (53%) and Lithuania (50.7%). A similar trend occurs for residential buildings (Fig. 2). Energy consumption by end-use in EU-15 member states is dominated by space heating (70%), followed by water heating (14%) and electrical appliances and lighting with 12% [3]. The share of space heating declined from 72.4% in 1985 to 69.6% in 2001, while it increased for electrical appliances and lighting from 10.3% in 1985 to 12.3% in 2001. Space heating ranges between 50% and 60% in Sweden and UK and 75% in Germany and The Netherlands. In southern Europe, it is about 50% in Spain and 30% in Portugal. On an average for the EU-15, the electrical energy consumed by appliances and for lighting represents about 60% of the total electricity used by the European households (53% in 1985).


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Fig. 1. Final energy consumption in the residential and tertiary sector of the EU-25 member states [1]. Bars (left scale) correspond to the buildings’ energy consumption in million tonnes of oil equivalent (Mtoe). The points and trend line (right scale) correspond to the ratio (%) of the buildings’ final energy to the total final energy consumption in each member state. The countries are arranged in ascending order of the percentage values.

Fig. 2. Final energy consumption in residential buildings of the EU-25 member states [1]. Bars (left scale) correspond to the residential buildings’ energy consumption in million tonnes of oil equivalent (Mtoe). The points and trend line (right scale) correspond to the ratio (%) of the residential buildings’ final energy to the total final energy consumption in each member state. The countries are arranged in ascending order of the percentage values.

Various factors influence energy consumption in buildings. Among them, envelope construction, age distribution of the existing building stock, outdoor weather conditions, number and size of buildings, type, age and efficiency of equipment, fuel split for heating and sanitary hot water production, which are outlined next. Some EU member states in northern Europe have already implemented various instruments, including strict building standards, taxes, and subsidies, and have successfully managed to reduce energy consumption for heating [18,19]. On an average, new European dwellings are about 60% more energy efficient than the ones constructed before the first oil crisis in the 1970s, and consume 28% less than dwellings built in 1985 [3]. Actually, the most significant improvement was observed after 1990 due to the stricter measures taken by several EU member states and the introduction of higher energy standards in the mid-1990s. As a result, dwellings built in 2002 consume 24% less than dwellings built in 1990. For example, in Germany, the Thermal Insulation Ordinance (TIO) (Wa¨rmeschutzverordnung) was revised three times, reducing thermal heat demand of new residential buildings, from 1977 to 1984

below 200 kWh/m2, 1984 to 1994 below 150 kWh/m2, and 1995 to 2001 below 100 kWh/m2 [20]. The first TIO in 1982 tightened the maximum U-values by 25%, while the second revision in 1994 introduced additional restrictions and a more integrative approach, defining maximum values for the building heating demand. Finally, the Energy Savings Ordinance (EnEV—Energieeinsparverordnung) for new buildings introduced in 2002 and revised in 2004, which replaced the TIO and Heating-Systems Ordinance (Heizungsanlagen-Verordnung), the annual net heat demand must be about 95 kWh/m2 (60 kWh/m2 for space heating, 25 kWh/m2 for domestic hot water and 10 kWh/m2 for generation, distribution losses). However, further tightening of the measures is required to meet the new EPBD and environmental objectives even in some northern European countries. For example, based on 1996 data, Ireland has the lowest proportion of double-glazed dwellings in northern Europe—only one-in-three Irish households are double-glazed compared with an average of over three-infive in northern Europe [17]. Cavity wall insulation have only a quarter of all houses in the UK and 26% in Austria, while floor insulation is limited to 4% in the UK and 11%



in Austria. Belgium also has a relatively energy inefficient dwelling stock, with just 12% of dwellings equipped with floor insulation and a third with roof insulation. On the other hand, countries like Finland, Norway, Sweden and to a certain degree Denmark, have exemplary levels of residential energy efficiency. The year of building construction provides useful insight information with regard to the type of envelope construction, in accordance to the national building standards in force at that time and in particular the use of thermal insulation and materials used for the building envelope or even the type of electromechanical installations. More than 50% of the existing residential buildings in EU-25 were built before 1970 and about 1/3 of the dwellings were built during the 1970–1990 [13]. The ownership status varies significantly, with privately owned dwellings averaging 70% throughout EU-25, ranging from over 80% in seven countries (Lithuania 87.2%, Hungary 86.9%, Estonia 85%, Slovenia 82.2%, Spain 81%, Greece 80.1%, Italy 80%), down to 43% in Germany and 38% in Sweden. Private rented dwellings average 18.5% throughout EU-25, ranging from over 51% in Luxembourg and 40.3% in Austria, down to about 9% in the UK, Estonia, Lithuania, 2.6% in Slovenia and much lower in Slovakia and Poland. Finally, social housing averages 9.4% throughout EU-25, ranging from 35% in The Netherlands and 27.2% in Denmark, down to low single digits in Spain, Luxembourg, Latvia, Hungary, Greece and Cyprus. The annual total energy consumption in residential buildings averaged 150–230 kWh/m2 in the 1990s [21]. In eastern and central Europe, the total energy consumption was 250–400 kWh/m2, often averaging about 2–3 times higher than that of similar buildings in western Europe. In Scandinavia, well-insulated buildings have an annual consumption of 120–150 kWh/m2, while the so-called low-energy buildings may even drop down to 60–80 kWh/ m2. From a recent audit campaign in 193 European residential buildings [19], the actual total heating energy consumption averages 174.3 kWh/m2 (the lowest value starting from 30.6 kWh/m2 in Greece and the highest reaching 763.3 kWh/m2 in Poland), with national averages of 144.1 kWh/m2 in Denmark, 108.4 kWh/m2 in Greece, 261.1 kWh/m2 in Poland and 172.0 kWh/m2 in Switzerland [19]. On the other hand, Swiss residential buildings bearing the Minergie quality label have a target value for an annual total energy consumption of 41.7 kWh/m2, while the German advanced low-energy buildings and Passivehouse standard, limits the annual energy demand for space heating to just 30 and 15 kWh/m2 [22], respectively. The EU-15 average annual energy consumption per dwelling, accounting for weather corrections, decreased by 0.8% pa between 1985 and 1990, remained stable between 1991 and 1996 and increased by about 0.4% pa during 1996–2001, reaching about 20,350 kWh per dwelling with climatic corrections and 19,420 kWh per dwelling based on actual data [3,23]. Although fossil fuel prices have significantly increased, in real terms, since 1999 there is

no visible impact on demand, while electricity prices exhibit a steady decline of about 1.2% pa. Northern European countries consume less energy for heating per unit floor area and heating degree-day (HDD). For example, heating energy consumption averages 43 Wh/ m2. HDD in Sweden and 46 Wh/m2 HDD in The Netherlands, and jumps to 77 Wh/m2 HDD in France [18] and 73 Wh/m2 HDD in Greece [19]. This is the end result of the more strict thermal regulations and other policies that are being enforced in northern European countries to tackle high heating energy consumption, as outlined above. Buildings in urban areas are also of particular interest in terms of increased cooling demand, since adverse outdoor conditions, as a result of higher outdoor pollution and the urban heat island effect, encourage the use of mechanical air-conditioning with a direct impact on peak electrical energy consumption [24]. From a recent study of a century long surface air temperature record in downtown Athens, the number of hot days as well as the frequency of occurrence and duration of warm events have significantly increased during the last decade, while a negative trend is observed in the frequency of low temperatures and the duration of cold events especially after 1960 [25]. Energy consumption for cooling has been growing strong during 1990–2000 reaching 14.6% pa as a result of increasing demand for comfort during summer and the price decrease of domestic air-conditioning equipment [15]. The number of installed central air-conditioning (CAC) systems in buildings has increased by a factor of 4.5 in the last 20 years [26]. Total CAC air-conditioned floor space has grown from 40 million square meters in 1985 to over 150 million square meters in 2000 [27]. Chillers (45%) and room air-conditioners (RAC) (36%) dominate the service sector air-conditioning market, based on 1998 data. A strong growth is also reported for RAC, with annual sales growing at an average of 12% [28]. Since 1990 the RAC stock in the EU has grown by an average of 35% pa, while annual RAC sales have doubled over the same period. The EU stock is estimated to reach 21 million by 2010. Annual energy consumption of RAC was 1.6 GWh in 1990, 11 GWh in 1996 and is estimated to reach 44 GWh in 2010. The resulting CO2 emissions in the EU are expected to increase by a factor of 20 from 1990 to 2010. Currently, Spain and Italy account for more than 50% of the EU market, in terms of air-conditioned floor area [26]. The cooled floor area per inhabitant, based on data for 2000 and estimates for 2020 in parenthesis, average about 3.2 (6.4) m2/inhabitant in EU-15, but varies significantly from country to country reaching 6.2 (11.5) m2/inhabitant in Spain, 5.8 (16) m2/inhabitant in Greece, 2.5 (7) m2/inhabitant in France, 5.6 (9) m2/inhabitant in Italy and 2.1 (11.5) m2/inhabitant in Portugal [29]. The equipment rate of RAC in Europe is about 5% in the residential sector and 27% in the tertiary sector [29], with a great growth potential compared to other countries like the USA (65% and 80%, respectively) and Japan (85% and 100%, respectively).


Energy consumption for electrical appliances increased by 1.9% pa as a result of the higher number of appliance use and stand-by power consumption [15]. Space and water heating has reached saturation and growth was limited to 0.5% pa [15]. The observed increase in number of households and reduction in average household size have serious environmental implications, including among others: changes in land use as more dwellings are needed, increasing number of electrical appliances, and consequently, a rise in total energy consumption [30]. The average size of households ranges between 2.2 and 3.1 persons, and has fallen from 2.8 persons in 1980 to 2.5 person in 1995, with many countries having a 10–15% reduction in household size during this period. The trend towards more and smaller households is a long-term one and the share of single-person household in EU is projected to climb from to 36% in 2015. The increased number of households creates a need for more buildings, which is further increased by the general trend towards bigger dwellings. The average size per dwelling in EU-15 has increased from 84 m2 in 1985 to 89.5 m2 in 2001, at an average annual rate of 0.4% or 0.3 m2 pa [3]. Small variations are observed between the EU member states from 77 m2 in Finland to 125 m2 in Luxembourg [9], while Cyprus has the largest recorded average dwelling size in the EU-25 at 145 m2 [31]. Overall, the average energy consumption per unit floor area is decreasing faster than the energy consumption per dwelling: 16% between 1985 and 2000, compared to 11% for the unit consumption per dwelling. As a result, the increasing size of EU-15 dwellings has offset about 5% of the achieved energy efficiency [3]. Increased energy efficiency, as a result of technical advances, is notable for all major equipment, including boilers for central heating, lighting, and appliances. However, it is estimated that about 10 million residential boilers are more than 20 years old, thus having a significantly lower thermal performance than the currently available units. On the other hand, proper maintenance is necessary in order to avoid a reduction of energy efficiency over time. Most member states have already introduced regulations for the annual maintenance of equipment, i.e. boilers. For example, the German Energy Savings Ordinance (EnEV) requires that all boilers installed before 1 October 1978 (estimated at 2 million in 2001) shall be maintained or replaced by the end of 2006, unless the burners have been replaced, in which case the dateline becomes 2008 [20]. However, in some member states, there are concerns with regard to the actual implementation in the event that there is no proper monitoring and verification and is practically based on market acceptability. For example, a study by the Organization for the Master Plan and Environmental Protection of Thessaloniki during the period 1988–1990 revealed that 60% of central heating boilers in Thessaloniki were above the CO2 emission limits, while only 25% were in compliance with national regulations that mandate annual maintenance. A similar study in Athens in the framework of Attika SOS

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programme performed by MEPPPW, concluded that 57% of central heating installations did not comply with the annual inspections and 20% were above the CO2 emission limits. New energy efficient electrical appliances and efficient lighting have also contributed significantly in the reduction of electrical energy consumption. For most electrical appliances, efficiency has improved by 20–30% since 1990, as a result of technical improvements. For the large electrical appliances, the cumulative decrease in European households is 130 kWh/household since 1992, which represents about 20 TWh electricity savings [3]. However, the average consumption for large appliances per household decreased by only 8% due to the increase use of more large appliances in the increased number of households; thus, the increase in appliance ownership offsets about 60% of the energy savings resulting from their technical improvements. The type of fuel and amount of energy used in residential buildings varies from country to country, depending on living and comfort standards, per capita income, natural resources and available energy infrastructure. For example, natural gas is common in most European countries and has infiltrated the residential sector, but in Greece it was only recently introduced in the energy market and is being used in a very small percentage of dwellings. In general, dwellings in developed countries use more energy than those in transitional or developing nations. Space and water heating account for most of the energy used by dwellings in the industrialized countries (North America, Western Europe and industrialized Asia). In European residential buildings, about 57% of the total final energy consumption is used for space heating, 25% for domestic hot water and 11% for electricity [32]. 2.2. CO2 emissions The main contributor to the total CO2 emissions from the EU-15 building stock in 2002 was the residential sector (77%), while the remaining 23% originates from nonresidential buildings [12]. During the period of 1990 to 2002, the largest decrease in absolute terms of CO2 emissions from households was observed in Germany with 7% ( 9190 kt CO2), as a result of improved efficiency in power and heating plants and the fuel switch in eastern German households, where in 2002 reached 120 090 kt CO2, and in Nordic countries with emission reductions of more than 1 million tones, as a result of the increased use of district heating [4]. The largest increase was observed in the UK with +11% (+8561 kt CO2) where emissions from households in 2002 reached 87 638 kt CO2. Three EU-15 member states, namely Germany, the United Kingdom, France and Italy, account for about 77% of the total CO2 emissions from households. The estimated technical potential of the overall emission savings for space heating, if all retrofit measures covered by EPBD were realized for all EU-15 building stock of 2002 at the same time, could reach 398 Mt per year, although this is



difficult to practically implement [12]. However, already there some positive signs. The average CO2 emissions per dwelling decreased by 17% during 1990–2001, outperforming the improved energy consumption per dwelling, which decreased by about 5% [3]. This was due to substitutions to less CO2 polluting energy sources (i.e., district heating, biomass and electricity). 2.3. The Hellenic situation In Greece, the final energy demand increased by 27.4% during the 1990s, reaching 19.5 Mtoe in 2002 [1]. Even during the previous energy crises, energy demand exhibited the sharpest increase among all European countries [33]. As a result, there was a significant increase in the production of electricity using lignite, which despite its low calorific value and high polluting potential, it is primarily used for power generation (currently about 63%) since it is the only national fossil fuel resource. The primary energy consumption per capita in Greece increased from 25,470 kWh/cap in 1990 to 29,890 kWh/cap in 2000 and reached 37,634 kWh/cap in 2002, but still well below the EU-25 average of 42,800 kWh/cap [1]. However, CO2 emissions per capita in Greece have climbed from 6998 kg/cap in 1990 to 8559 kg/cap in 2002, although the EU-25 average dropped from 8566 kg/cap in 1990 to 8233 kg/cap in 2002. Energy related activities including extraction, distribution and combustion of fossil fuels are responsible for about 76% of the total national annual GHG emissions, while during the period 1990–1995 the CO2 emissions from the energy sector accounted for about 90% of the total CO2 emissions in Greece [34]. Greece had in absolute terms the second largest increase of CO2 emission from households during the period of 1990–2002, with +82% (+3834 kt CO2), reaching 8518 kt CO2 in 2002 [4]. The Hellenic Building Thermal Insulation Regulation (HBTIR) (OHJ 362/4-7-79) has been in use since 1980 and sets the minimum requirements for thermal conductivity of the building envelope for different climatic zones. As a result, the great majority of the Hellenic building stock is not thermally insulated, despite the fact that the HDDs range reach over 2600 HDD in the northern parts of the country, due to the weather types affecting Greece with severe cold and rainy weather conditions during the cold period of the year between late October and early April [35]. According to 1990 data for Hellenic dwellings [36], 95% of the external walls, 99% of floors, 87% of pilotis, 70% of the roofs have no thermal insulation, 98% have no double glazing, and 96% of the heating distribution pipes are not insulated. Based on 1996 data [17], there has been some limited improvement, with 12% of households having cavity-wall insulation and 8% are double-glazed. A few additional national laws and regulations have also been introduced in Greece, in accordance to the EU directives for the rational use of energy and the abatement of emissions, like the annual maintenance of central

heating boilers (Official Hellenic Journal—OHJ 143/A/29-93) that mandates annual flue gas analysis and performance testing of boilers and the energy labeling of electrical appliances (OHJ A114/7-7-94). In accordance to the General Building Regulation and the common Ministerial Decision (OHJ 880/B/19-8-98) there is a new energy code under development (Regulation on Rational Use and Energy Conservation in buildings (RRUEC)) in accordance to the EPBD (2002/91/EC). The climatic zones defined in accordance to the proposed RRUEC are based on the HDDs: Zone A (601–1100 HDD), Zone B (1101–1600), Zone C (1601–2200) and Zone D (2201–2620). The following sections present an overview of the relevant data for the Hellenic dwellings stock and energy consumption, in order to extract the necessary data used in the follow-up analysis on the assessment of ECMs and CO2 reduction.

3. Hellenic dwelling stock The breakdown of the Hellenic building stock for different periods of construction is illustrated in Fig. 3. The buildings constructed before 1980 (pre-1980) correspond to 74.6% of the total building stock. These buildings are not thermally insulated and exhibit a poor energy performance, while for the vast majority of them they are equipped with old electromechanical installations [37]. The percent of buildings that have been constructed during 1990s, is estimated based on the building construction activity for this period [38]. The main categories of the Hellenic building stock according to end use of the buildings are: dwellings, hospitals, hotels, schools and offices/commercial buildings (Fig. 4). There are also other uses including industrial buildings, churches, athletic facilities, storage areas, closed parking spaces, etc., which account for 21.9% of the total stock, the majority of which have periodic use and a limited overall contribution to the total energy consumption. Residential buildings account for about 75% of the Hellenic building stock. The Hellenic residential building stock was classified in three categories according to the year of building construction. The first category includes the buildings constructed before 1980 (pre-1980), which is considered the 1991-2001 8%