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Contents lists available at ScienceDirect

Energy and Buildings

journal homepage: www.elsevier.com/locate/enbuild

Building stock characteristics and energy performance of residential

buildings in Eastern-European countries
Tamás Csoknyai a,∗ , Sára Hrabovszky-Horváth a , Zdravko Georgiev b ,
Milica Jovanovic-Popovic c , Bojana Stankovic c , Otto Villatoro d , Gábor Szendrő a
a
Budapest University of Technology and Economics, Műegyetem rkp. 3-9., 1111 Budapest, Hungary
b
Sofia Energy Agency—SOFENA, 65 Tsar Ivan Asen II Street, 1124 Sofia, Bulgaria
c
Faculty of Architecture, University of Belgrade, Bulavar Kralja Aleksandra 73/II, Beograd, Serbia, Serbia
d
STÚ-K, a.s., Building Engineering-Consultants, Saveljevova 18/1629, 147 00 Praha 4, Czech Republic

a r t i c l e i n f o a b s t r a c t

Article history: Countries in Eastern-Europe have similar characteristics due to their common historical and economic
Received 1 December 2015 backgrounds. A large part of the housing stock has been built during the Soviet era, applying uniform
Received in revised form 20 June 2016 solutions and similar standards, but similarities extend to other periods as well. On the other hand,
Accepted 21 June 2016
the differences should also be noted – although the climate is mainly continental, there are significant
Available online xxx
variations between South and North and between mountainous and flat areas.
In this paper, a detailed comparative analysis is presented for Bulgaria, Serbia, Hungary and the
Keywords:
Czech Republic. The results are based on the residential building typologies developed within the TAB-
Housing stock
Eastern europe
ULA/EPISCOPE project co-funded by the Intelligent Energy Europe Programme. Typical building types
Building typology will be presented, covering building structures and systems. Important energy performance indicators
Energy saving are identified and compared, supported by available statistical data about the housing stock.
Potential The added value of the paper consists of the analysis of heterogeneous data sources and collecting and
Large panel buildings comparing the information of the housing stock under a common comparison framework of building
User behavior typology data between countries, and the contribution in the harmonization of the building typology
District heating approach.
Bottom-up approach
© 2016 Elsevier B.V. All rights reserved.

1. Introduction and political developments. After accession, European initiatives,

particularly the EPBD [1] have determined the progress of energy
Residential buildings in Eastern Europe exhibit numerous sim- regulations, but the economic limitations remained an important
ilarities in their design, building envelope, ownership structure factor. In three of the countries discussed in this paper, the impact of
and even user habits. A large part of the building stock has been Austria-Hungary (Austro-Hungary Empire) was also notable before
built during the Soviet era using uniform solutions and similar the First World War, particularly in major cities in the region.
standards. Some of these similarities persisted even after the demo- Large housing estates (panel buildings) are an important, almost
cratic changes in these countries, mostly due to similar economic iconic, common element of the building stock in Eastern Europe,
meriting a closer look. These large, monotonous blocks of flats,
mostly using prefabricated sandwich panels, have become a symbol
Abbreviations: AC, air conditioning; BG, Bulgaria; CDD, cooling degree days; CHP, of the Soviet era. They have similar characteristics and problems,
combined heat and power; CZ, Czech Republic; DH, district heating; DHW, domes- and thus have been the focus of energy policy discussions in
tic hot water; EER, energy efficiency ratio; EPBD, energy performance of buildings most countries with a large stock. The seventies and eighties were
directive; EPISCOPE, Energy Performance Indicator Tracking Schemes for the Con- the “finest moments” of industrialized technology, when this was
tinuous Optimization of Refurbishment Processes in European Housing Stocks; HDD,
heating degree days; HU, Hungary; IND, building built with large panel blocks; MFH,
the construction method of choice. The technology was actually
multi-family house; NZEB, nearly zero energy building; PM, particulate matter; RS, invented in the West, first used in Denmark, England, France and
Serbia; SFH, single family house; TABULA, Typology Approach for Building Stock other countries in large numbers before the Soviet Union procured
Energy Assessment; U, thermal transmittance. the right to use the technology and developed its own systems. In
∗ Corresponding author.
Russia, most of the apartment buildings were constructed between
E-mail addresses: csoknyaitamas@gmail.com, csoknyait@mail.bme.hu
(T. Csoknyai).
1960 and 1985 and as a result, the urban housing stock today con-

http://dx.doi.org/10.1016/j.enbuild.2016.06.062
0378-7788/© 2016 Elsevier B.V. All rights reserved.

Please cite this article in press as: T. Csoknyai, et al., Building stock characteristics and energy performance of residential buildings in
Eastern-European countries, Energy Buildings (2016), http://dx.doi.org/10.1016/j.enbuild.2016.06.062
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sists mainly of a few standard building types [2–4]. The share of sumption of the Czech households (types of fuel, frequency of
such dwellings in the countries described in this paper is 16.7% system types and their age structure, energy consumption) [22].
on average, representing a moderate figure in the region. Just to A new ENERGO 2015 micro-census is underway, but results are not
provide a frame of reference: Slovakia has 778,000 such build- yet available. In the meantime, other efforts to analyse the energy
ings, representing 40% of the residential building stock [5] the consumption of the Czech residential sector have been carried out.
same figure in Poland is 6,171,000, (49%) [6]. The proportion of PanelScan 2009 focused on analysing the renovation perspectives
these buildings is particularly high in the Baltic countries [7,8]. To of residential large panel buildings including renovation progress
give an example: in Estonia, 45% of the dwelling stock has been and estimation of the required investment to renovate the rest of
built between 1961 and 1990 – multi-storey apartment buildings, the large panel building stock [23]. More recently, studies have
mostly with prefabricated technology [9]. In Romania, 29.4% of the been performed to provide a current overview of the energy saving
dwellings are in apartment buildings, 68.3% of which consist of potential in the housing stock [24–27]. The study “Building Ren-
large panel buildings [10]. In former East Germany, more than 2 ovation Strategy” by Holub and Antonín [26] is of special interest
million of such flats exist today [11]. since it tries to close the gaps of the previously mentioned censuses
In light of the above, there is currently a gap in available lit- and studies, by using the concept of the TABLE/EPISCOPE residential
erature: comparing different countries is problematic because of typology, the same approach applied in the present paper. In fact,
the heterogeneity of available data, even in countries that have a the aforementioned study was later included in the Czech National
similar historical, economic and social background like the ones Energy Efficiency Action Plan [28] demonstrating that the assess-
presented herein. Therefore. this paper aims to fill this gap by ment of the energy saving potential and investment required to
attempting to provide a comparative analysis for the residential renovate the overall Czech housing stock is not only of academic
building stock of four countries in Eastern Europe: Bulgaria, Serbia, interest but also presents valuable information to policy makers.
Hungary and the Czech Republic. First, qualitative similarities and In Refs. [29,30], a country profile for Serbia has been elaborated.
differences between these countries will be discussed, covering the It includes statistical information about the Serbian building stock,
most important aspects influencing the thermal performance of albeit in much less detail and without energy performance analysis.
the building stock and future development perspectives. After this First attempts to formulate a methodology for energy performance
baseline has been established, a comparative analysis of selected characterization of the residential building stock have been made
important energy performance indicators will be presented based in the framework of the national research project titled “Energy
on the results of the TABULA/EPISCOPE building typology [12]. For optimisation of buildings in the context of sustainable architecture
the purposes of this paper, policy implications are forgone in favor (NRP 283, 2002–2005), and the published material [31,32] served
of the technical aspects of the comparative analysis. as the methodological milestone for further research. Although the
Beside the similarities, some important differences should also formulated methodology included all relevant aspects of energy
be noted. Although the climate is mainly continental in the region, performance characterization, showcased in the example of Bel-
it gets colder from South to North and solar gains become less sig- grade residential building stock, it lacked the tool for assessing the
nificant. There are differences in economic development, as well as entire residential stock on the national level. The most detailed and
political priorities. The differences in the energy mix are also sig- comprehensive analysis has been carried out for Serbia through
nificant, having an impact on building service systems and the level the collaboration within the TABULA/EPISCOPE project. The results
of system centralization. of this research, which included a statistically relevant survey
In order to perform a comparative analysis of the residential of the national residential building stock, and its energy perfor-
building stocks in the selected countries, we have used avail- mance characterization, have been published in several studies
able statistics and the building typology in a bottom-up modelling [29,33–35]. The results of this work are further developed in this
approach. The typology itself has been developed as part of the paper. Formulation of typology and methodology for energy per-
TABLE and EPISCOPE projects, supported by the Intelligent Energy formance characterization of the building stock has enabled a more
Europe Programme with the participation of 18 EU countries, detailed analysis of specific groups of residential buildings within
Norway and Serbia [12]. The results of these projects have been the typology, as the one selected in this paper. Also, case studies
published in several scientific articles, all with a different focus: of the refurbishment potential of representatives of the selected
the residential building stock of Greece has been modelled using group of residential buildings can be found throughout available
the typology developed [13], while [14] demonstrated the energy literature [36–38].
performance of French residential buildings from a fuel poverty The potential for decreasing carbon dioxide emissions from
perspective using national statistics. In Ref. [15], the differences Hungarian residential buildings have been analyzed by [39]. The
between top-down and bottom-up approaches in energy statistics simplified building stock model in this reasearch can be consid-
has been showcased for Denmark. Research has also been carried ered as a preliminary step for the detailed typology developed in
out on a larger scale in Ref. [16], identifying 72 building types in our research. The most detailed building energy performance anal-
the entire EU-25. The buildings were classified in terms of their ysis has been carried out recently in 2015 within a representative
representativeness, geographical distribution, size, material com- field survey within the KEOP-7.9.0/12-2013-0019 project, selecting
position and thermal insulation, grading renovation options based 2000 buildings [40], using the experiences of TABULA/EPISCOPE.
on their life cycle impacts. Using yet another approach, statistics However, the results of this project are not publicly available as of
and surveys have been used to analyse the energy performance of this writing.
Greek residential buildings in Ref. [17]. Finally, the ENTRANZE project should be mentioned with a focus
There have been several studies in the past that focused on on displaying building data (less detailed than this paper) with a
the building stock in the analyzed countries. The national cen- user-friendly mapping tool and on the development of scenarios
suses were carried out in 2011 in all countries. They give a general for building renovations for the EU-28 countries and Serbia [41–43].
overview of the housing stock [18–21]. The censuses, however, do About Bulgaria only the TABULA/EPISCOPE and ENTRANZE projects
not provide enough information about the energy performance of can be mentioned as previous works to assess the entire residential
the housing stocks. The Czech residential building stock has been building stock.
previously analyzed from different perspectives. From the energy The added value of the paper consists of the analysis of heteroge-
consumption perspective, only small-scale studies are available. neous data sources and collecting and comparing the information
The ENERGO 2004 micro-census shed light into the energy con- of the housing stock under a common comparison framework of

Please cite this article in press as: T. Csoknyai, et al., Building stock characteristics and energy performance of residential buildings in
Eastern-European countries, Energy Buildings (2016), http://dx.doi.org/10.1016/j.enbuild.2016.06.062
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building typology data between countries, and the contribution in determine the primary energy demand for heating and domestic
the harmonization of the building typology approach. hot water, the distribution of energy carriers and technical building
systems according to types of buildings were taken into consider-
ation as described in Sections 3.2.2–3.2.4.
2. Methodology Cooling was not considered in the model, for two reasons: on
the one hand, although cooling is a growing factor in the energy
In the Section 3, the regional characteristics are described cov- use residential buildings, it is still not dominant, and on the other
ering several aspects: climate, building statistics, typical building hand, available statistical data on the ratio of residential buildings
constructions, energy sources, typical technical building systems, with cooling is insufficient for drawing conclusions. This is a data
user habits and renovation actions carried out so far. This descrip- gap that merits further research, but a solution is beyond the scope
tive section is exhaustive and detailed as it is mainly based on of the present paper.
national data sources and studies available in national languages The first objective was the determination of the current energy
only. performance of the building types. The applied building character-
The second part covers the quantitative comparative analysis. istics were based on the building stock analysis described in Section
Calculations are based on the TABULA/EPISCOPE project results 3.2.
[12]. The 20 project partners developed national building typolo- The second objective was to determine the energy saving poten-
gies representing the residential building stock of their countries. tial achievable with deep renovation targeting a level close to nearly
The buildings have been classified and a national building type zero building energy (NZEB) requirements. These requirements are
matrix has been developed for each country. For each building defined on national level based on the EPBD [1,46–48]. A com-
type, a real example building has been selected to represent the mon element of the national legislations is that they consist of
characteristics of the type; subsequent calculations have been car- different levels: U-values of the building shell are maximized, min-
ried out with the common TABLE tool. An exception was Serbia, imum requirements on technical building systems are set, overall
where a national calculation tool has been used (Serbia participated energy performance or CO2 emission levels are maximized and
on a voluntary basis in the project) based on the same principles. there are additional requirements on mandatory application of on-
Thus, energy performance indicators have been determined for site or nearby renewable energy sources. In Serbia, the official NZEB
each building type. However, it was not an objective of the TAB- requirements have not yet been defined, therefore the targeted
ULA/EPISCOPE project to elaborate cross-country comparisons. The level had to be defined based on top quality technical solutions
comparative analysis of the four countries have been elaborated for available on the Serbian market. Definitions of other countries in
this paper. the region have also been taken into account. The EPBD requires the
The parameters for classification of residential buildings accord- NZEB level for new buildings only but not for renovations, there-
ing to the TABLE concept were the country, the region (national fore the NZEB level was merely an indicative target in our models,
or region of the country), the construction year together with the in cases of technical and economic difficulties the applied mea-
building size class and several additional parameters. sures were slightly less ambitious. The exact renovation actions
The TABULA/EPISCOPE typologies consist of a high number have been defined case by case. More detailed descriptions of the
(mostly between 15 and 40) of building types [12]. For the research current state and retrofit levels per building type can be found on
presented in the paper, building types have been merged into a the EPISCOPE website [12] and in Ref. [33]. A meaningful compari-
smaller number of classes to make the analysis more compara- son of the NZEB definitions is problematic to make because country
ble and the results more illustrative. The indicators of the merged definitions vary widely – the primary energy requirement depends
classes were determined as the weighted average of the TAB- on the A/V ratio in Hungary, as opposed to the use of the reference
ULA/EPISCOPE building type indicators using the national total floor building methodology in the Czech Republic, for example. As for
area as the weight. Vacant buildings were excluded from the anal- the heat transfer coefficients, the requirements also differ. Some
ysis. countries define values for each structural element, while in the
The energy need for space heating of all the building types Czech Republic, the average U-value of the building envelope must
were calculated by applying the seasonal method according to EN be below 70% of that of the reference building. Therefore, poten-
ISO 13790 on the basis of a one-zone model [44]. As explained tial comparisons are limited by these circumstances to renewable
above, the common TABLE calculation tool has been used for Bul- energy ratios.
garia, Hungary and the Czech Republic [12], whilst for Serbia the First, the energy performance calculations have been carried out
KnaufTermPro2 software has been applied. The external boundary per building type for the current and the renovated state. Then
conditions (external temperature and solar radiation) are based on sectorial level calculations were done by multiplying the specific
the climate data of the different countries. Standard values are used indicators with the national total floor area. The energy saving
for the utilization conditions (e.g. room temperature, air change potential has been calculated as the difference between figures
rate, internal heat sources, energy need of domestic hot water) as belonging to the renovated state and the current levels. It is the so-
described in Table 1 [12]. The common reference area is the condi- called bottom-up approach widely applied in literature with the
tioned floor area calculated on the basis of internal dimensions. goal of evaluating the effect of different energy saving measures,
The calculations have been carried out assuming continuous e.g. [49–52].
heating, which means that the impact of user habits is not taken
into account. As explained in Section 3.3, available data on heating
habits is insufficient in all of the countries. 3. Description of the region and the building stock
Net delivered energy for heating and domestic hot water has
been calculated from the energy need, covering all system and con- 3.1. Climate
trol losses inside the buildings. Then, primary energy calculations
have been carried out taking into account the energy required for The energy performance of the building stocks cannot be ana-
extraction, processing, storage, transport, generation, transforma- lyzed without taking climatic conditions into account. The climate
tion, transmission, distribution, and any other operations necessary is generally continental with hot summers and cold winters, but
for delivery to the building applying primary energy factors as there are important differences that should not be neglected. The
described in EN 15603 [45] in accordance with the EPBD [1]. To Czech Republic is in the Northwest, where the climate is gener-

Please cite this article in press as: T. Csoknyai, et al., Building stock characteristics and energy performance of residential buildings in
Eastern-European countries, Energy Buildings (2016), http://dx.doi.org/10.1016/j.enbuild.2016.06.062
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Table 1
Episcope standard values used in the calculations [12].

Single-unit housing Multi-unit housing

internal temperature [◦ C] 20
air change rate [1/h] 0.4 0.4
net energy need domestic hot water [kWh/(m2year)] 10 15
average internal heat sources per m2 reference area [W/m2 ] 3

ally colder and more humid. Bulgaria is in the Southeast, where Values of total floor area for different building classes are shown in
summers are hotter and winters are milder. In addition to the geo- Fig. 1.
graphical position, the influence of altitude can also be of great Regarding the number of dwellings, more than the half (58.2%)
importance: Serbia and Bulgaria are strongly affected by moun- are located in detached houses, but there are notable differences
tains, the Czech Republic is hilly, whilst Hungary is dominated by between the countries: the highest share belongs to the Republic
plains. of Serbia (73%), followed by Hungary (62%), Bulgaria (56%) and the
All this is reflected in the national calculation standards and Czech Republic (45%).
methods. The Czech Republic is divided into four climatic regions Dwellings in large panel buildings are less significant, but
with rated outdoor temperatures of −12 ◦ C, −15 ◦ C, −18 ◦ C and remarkable (17.6% in average), particularly in the Czech Republic
−20 ◦ C (ČSN 730540, Annex H1). The average HDD (Eurostat, NUTS- (26.9%).
2, 2010–2013) in the Czech Republic is 3495 days ◦ C/year [53]. In The remaining dwellings (16.1–29.3%, on average: 24.2%) are
general, the country has a temperate continental climate, usually located in other types of multi-flat buildings.
with warm summers and cold winters. The temperature differences Most dwellings were built during the Soviet era (61% on aver-
between these two seasons are relatively high. age), this type of buildings has a particularly notable share in
In Hungary, three climate zones have been defined by the heat Serbia (74%), while the other countries have roughly the same share
loss calculation standard for sizing heating systems with rated out- (56–59%). A considerable portion of the building stock has been
door temperatures of −11 ◦ C, −13 ◦ C, −15 ◦ C [54]. No climate zones built before the end of WWII, with the highest share in Hungary
are defined in the energy performance calculations and degree days (29%) followed by the Czech Republic (22%), Bulgaria (14%) and
of 3000 days ◦ C/year are applied all over the country [46]. Serbia (12%). On average only 19% of the dwellings were con-
The Serbian climate is between a continental climate in the structed after the end of the Soviet era in the four countries. Such
North with cold winters and hot, humid summers with well dis- new dwellings have the highest proportion in Bulgaria (27%), fol-
tributed rainfall patterns, and a more Adriatic climate in the South lowed by the Czech Republic (19%), Hungary (15%) and the Republic
with hot, dry summers and autumns and relatively cold winters of Serbia (14%). In general, Bulgaria has the youngest building stock
with heavy inland snowfall. New regulations on energy efficiency – about half of the buildings have been constructed in the past 40
[55] have abandoned using climatic zones and introduced calcula- years and only 3.9% before 1919, however their condition is dete-
tions based on HDD. Official heating degree days are available for riorating due to poor maintenance and facility management. Over
most cities in Serbia [55], the average HDD is about 2600. 50% of the Czech housing stock was built after 1970, the average
Bulgaria is divided into 9 climate zones. Only heating degree age of buildings is 49.3 years for family houses and 52.4 for other
days are defined in the legislation from 2100 to 2900 days ◦ C/year residential buildings [12,33,18,20,21].
depending on the climate zone. The mildest zones are in the South The significant share of vacant buildings is also worth noting.
and by the Black Sea. The importance of summer cooling cannot be There is a continuous trend of abandoning apartments and houses
overstated – although electricity plays an important role in heat- in certain regions due to urbanization worsened by declining pop-
ing, peak electricity consumption occurred in hot summer days ulations. Only 83.4% of the dwellings are occupied in the Czech
in recent years due to higher comfort needs in offices, residential Republic, the rest (16.6%) are vacant, either unsuitable for use or
buildings and summer hotels near the Black Sea as well as climate abandoned [18]. In Serbia, 75% of buildings are occupied, 14.7%
change. temporarily unoccupied, 3.5% abandoned, 5.5% are used for vaca-
Average cooling degree days for the last 5 years for an indoor tion purposes and the majority of non-inhabited units is located
temperature of 26 ◦ C are as follows: Prague (CZ): 17 days ◦ C, in small communities [19]. In Hungary, 10.9% of the dwellings are
Budapest (HU): 75 days ◦ C, Belgrade (RS): 130 days ◦ C, Sofia (BG): uninhabited [20]. In Bulgaria, 83.7% of the residential buildings are
89 days ◦ C, Plovdiv (BG): 137 days ◦ C [56]. occupied [21].
The indicated HDDs relate to an average indoor temperature In Eastern European countries, most of the dwellings are pri-
of 20 ◦ C except for Bulgaria, where the design value is 19 ◦ C vately owned. Both in Bulgaria and Hungary, 96% of the dwellings
[46,56–59]. are private [20,21], even more in Serbia (99%, [60]). In the Czech
In order to determine solar gains during the heating sea- Republic, 9% of the dwellings are owned by the state and munic-
sons solar irradiation values were taken into account according ipalities. The rest (91%) is either owned by natural persons (46%),
to orientation (e.g. for a horizontal surface the values are housing co-operatives (11%) and other types of ownership (34%)
as follows: Bulgaria: 337–410 kWh/m2 year, Czech Repub- [18].
lic: 354–416 kWh/m2 year, Hungary: 400 kWh/m2 year, Serbia: This property structure leads to a particular problem. Invest-
398 kWh/m2 year) [46,55,57,58]. ments in the renovation of multi-family buildings require a
complicated procedure and the support of all owners, whose finan-
cial situations are extremely varied, making the retrofit of multi-flat
buildings impossible without significant subsidies.
3.2. Description of the building stock

The housing stocks of the analyzed countries have several 3.2.1. Building structures
similar characteristics. The overall stock consists of 15.3 million Building structure properties are less divergent for buildings
dwellings (4.4 million in Hungary, 4.0 million in the Czech Repub- built before the end of the Soviet era, after that, the differ-
lic, 3.7 million in Bulgaria and 3.2 million in Serbia) [18,20,21,33]. ences between countries become more noticeable, resulting from

Please cite this article in press as: T. Csoknyai, et al., Building stock characteristics and energy performance of residential buildings in
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Fig. 1. Total floor area according to age and type.

different economic performance and prospective dates for the ing became dominant in the Czech and Hungarian market in the last
introduction of EPBD requirements. two decades. Such insulating windows have become commonplace
Façade walls were typically not insulated until the end of the in Bulgaria since 2005 and in Serbia only since 2011 when the new
communist era with the exception of panel buildings in the Czech building code made their use obligatory. [12,33,40,61,64].
Republic, Serbia and Hungary, where the prefabricated reinforced
concrete sandwich panels contained a 5–8 cm insulation layer. In 3.2.2. Energy supply and heating systems
Bulgaria, the sandwich construction was introduced during the The centralization of heating decreases from Northwest to
years with the last system improvement in 1987. However, these Southeast. District heating is notable in all countries, particularly
insulated structures had very significant punctual thermal bridge in the Czech Republic. Natural gas is dominant in Hungary, but also
losses due to the steel reinforcing elements and the linear ther- important in the Czech Republic. Wood and electricity are the dom-
mal bridge losses at the panel junctions. Typical U-values are inant energy sources for heating in Serbia and Bulgaria, used in
0.9–1.5 W/m2 K for masonry constructions and 0.7–1.64 W/m2 K for decentralized units.
the large panel buildings [61]. Country-specific U-values are shown In the Czech Republic, 21.9% of the dwellings have room heat-
in Table 2. ing, 43.2% central or apartment heating, whilst 34.9% have district
After the end of the communist period, the U-values improved or collective heating. As of 2009, natural gas was the most impor-
significantly when insulating walling blocks started to dom- tant energy source (39%) for heating, followed by district heating
inate the markets, mainly in the Czech Republic, followed (36.84%), solid fuels (17.62% – mostly wood), electricity (6.25%) and
by Hungary. Insulated façade walls became increasingly fre- other sources (0.2%) [65]. In the case of gas heating, 82.2% of the
quent in these countries, particularly after introducing the EPBD dwellings have boilers and the rest (17.2%) have individual heating
requirements after 2006. Typical U-values in this period: Czech units (e.g. gas convectors). In case of wood-based heating systems,
Republic: 0.25–0.38 W/m2 K, Hungary: 0.3–0.5 W/m2 K, Serbia: central systems are more common (59.8%) than in individual stoves
0.46–0.9 W/m2 K, Bulgaria: app. 0.9 W/m2 K [12,33,61]. (40.2%) [22].
Applying insulation on the roof attic slab and on the roof In Hungary, 17.3% of the dwellings are heated by district heating,
started in the seventies and eighties, particularly in Hungary, Bul- 3.0% by central heating, 35.4% by apartment heating and 44.2% by
garia and the Czech Republic. After the end of the communist room heating. The dominant energy source is natural gas, but wood
period, roof and attic slab insulation also became common in multi- is also important in detached houses. Electric heating is rare [20].
flat buildings in Serbia with lower insulation thicknesses. Typical In Serbia, the main energy sources for heating are electricity
U-values after the end of the communist period: Czech Repub- (41.5%) and wood (27.7%), followed by district heating (12.8%),
lic, Hungary: 0.2–0.35 W/m2 K, Serbia: 0.3–2.5 W/m2 K, Bulgaria: coal (8.8%), natural gas (6.6%) and oil (2.5%). In the majority of
0.65–1.08 W/m2 K. Non-insulated roofs and attic slabs (typical until the dwellings, room heating is applied with low-efficiency wood
the seventies) have a U-value of 1.2–2.5 W/m2 K [12,33,61,64]. stoves, electric stoves or split units [66].
All countries used secondary glazing windows due to the cold In Bulgaria, wood (34.1%) is the most important energy source
continental winters with U-values between 2.5 and 3.0 W/m2 K. for heating, followed by electricity (28.6%), coal (19.8%) and dis-
Double glazed windows with low-emissivity coating and argon fill- trict heating (16.4%). Natural gas and other sources are negligible

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Table 2
Country-specific U-values [46,33,24,40,61–63,25].

Building constructions U-values [W/m2 K]

Hungary Bulgaria Serbia Czech Republic

Old buildings before 1990 (buildings built with traditional technology)

Façade walls 0.94–1.36 1.0–1.6 0.9–1.7 0.96–1.43
Attic slab/roof 0.36–2.1 0.5–2.1 0.65–2.47 0.35–1.25
Windows 2.5–3.0 2.3–2.65 3.0–3.5 2.7–2.8

Buildings built with industrialized technology

Period 1967–1991 [36] 1962–1996 [46] 1960–1990 [53] 1957–1991 [28]
Façade walls 0.7–1.5 0.8–1.3 1.1–1.64 0.8–1.1
Attic slab/roof 0.4–0.9 1.5–2.5 0.38–1.73 0.35–0.85
Windows 2.5–3.3 2.5–2.8 3.0–3.3 2.6–3.0

New buildings (after 1990)

Façade walls 0.22–0.49 0.8–1.0 0.46–0.92 0.25–0.38
Attic slab/roof 0.2–0.35 0.65–1.08 0.3–2.47 0.2–0.35
Windows 1.4–2.0 1.3–2.0 (since 2005) 1.3–1.5 (since 2011) 1.2–1.8

[21]. Wood logs and coal are mostly used in low-efficiency stoves, ing technology in the future, as evidenced by the scenarios and
leading to environmental problems in several villages and towns predictions in key strategic documents. The technical conditions
during the winter season due to high levels of PM and resulting of heating networks are diverging. Some networks are modern
health problems [67]. and efficient, but many are deteriorated and will require consid-
Renewable energy use in households in the region is dominated erable investments in the coming years. Development pathways
by biomass, the penetration of solar systems and heat pumps is still include modernization, network widening (which is a challenge)
low in the residential building stock [18,20,66,21]. and changing the energy source: increase in biomass, use of com-
Although wood has an important share in these countries, it munal waste and cogeneration [71–76]. The distribution losses of
should be noted that wood logs are mainly burned in old stoves the district heating network are significant in the region, approxi-
with 30–40% efficiency – a suboptimal way to use biomass. A mately 20% for Serbia [36]. In Bulgaria, distribution losses in district
large part comes from private forests, sold on the black mar- heating for the period 2005–2011 increased from 19 to 23% due
ket (directly from trucks at certain locations in the cities or even to reduced consumption, the deterioration of the system and lack
directly ordered separately), which means that the role of wood is of investment (excluding the district heating in Sofia) [77]. In the
probably much higher in reality than the national statistics would Czech Republic, the distribution networks have been modernized
imply [68,69,34,70]. and thus are in a better state: losses vary between 6 and 14% [78].
In the Czech Republic, Hungary and Bulgaria, most buildings
3.2.3. Domestic hot water (DHW) have substations with heat exchangers for heating and hot water
Available statistics on domestic hot water systems are limited. with modernized controllers and valves. The control corresponds
In the Czech Republic, only 0.23% of occupied dwellings lack tap to the external temperature and the building needs, and is imple-
water, and only 1.64% have no hot water, in both cases, most of the mented at three levels: on the district level (the temperature of the
dwellings are in buildings built before 1945 [18]. The three main supply water), in the building substations and in the premises with
sources of energy for DHW are district heating (32%), electricity thermostatic valves. Hungary is an exception regarding the third
(30.55%) and natural gas (23.43%). Only 0.21% (8505 dwellings) use level (thermostatic valves), which is found only in a part of the
a solar thermal system as a main source for DHW [18]. buildings. Most buildings are connected to district heating by heat
In Hungary, hot water is produced mostly by individual gas boil- exchangers in individual substations (indirect systems) in Serbia as
ers with or without indirect storage tanks or by individual electrical well, and the substations are equipped with heat meters, but in a
storage and occasionally, non-storage water heaters. In buildings few small cities there is direct connection (no heat exchanger). In
supplied by district heating, the heat source is mostly district heat- addition, in most flats there are no thermostatic valves and heat cost
ing with central storage tanks and a circulation pipeline [40]. allocators, thus floor area is used as the basis for payment instead
In Serbia, most domestic hot water systems include individual of measured consumption [71,72,77,34].
electrical, storage and occasionally, non-storage water heaters even District heating has not been lucrative in Hungary due to its price
in buildings supplied with district heating. In households with gas being high, but that has started to change as a result of the actions of
heating, there is a significant percentage with an integrated DHW the government (prices have been cut multiple times since 2012).
system. According to census data (2011), 75% of occupied dwellings Payment has been based on real consumption since 2003.
are connected to the public water system, and about 10% has gas In Serbia, district heating is still regarded as an indication of a
heating installed [19]. higher living standard. It is favored mostly because of its reliability
In Bulgaria, DHW systems mainly use electric heaters and stor- and relatively low price due to the flat rate payment system. Plans
age. Dwellings connected to district heating mostly use that for for the future include introducing a system of payment based on
DHW as well [12]. real consumption, increasing the share of natural gas, wood and
landfill gas in the energy mix, and including DHW systems that are
3.2.4. District heating (DH) generally based on electricity in collective housing units. In order
District heating networks were built in the seventies and eight- to reach the target of 40% of households being connected to DH
ies in order to supply heat for the large panel blocks (large panel system, some 100,000 new households have to be connected [71].
buildings). As described above, district heating still plays an impor- After 1989, most of the district heating utility companies in
tant role in all the countries, with a small downtrend in the last few small cities in Bulgaria were closed due to reduced loads both from
years, particularly in the Czech Republic and Hungary. National the household and the industrial sector, lack of investments and
energy strategies predict that despite current trends towards increasing fuel costs. Although most networks have been renovated
decentralization, district heating will remain an important heat- in the past decades, transmission losses are still high, as described

Please cite this article in press as: T. Csoknyai, et al., Building stock characteristics and energy performance of residential buildings in
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above. The national energy strategy foresees keeping the role of marginal in the Czech Republic [41]. However, the significance of
DH and modernization of the network and facilities (including the these systems is expected to increase in the future [76].
replacement of existing CHP capacities) [77]. The increasing popularity of individual cooling systems is often
criticized from an aesthetic point of view, because the outdoor units
3.3. Energy poverty and human factors are an unsightly addition to the facades. It is a particular problem in
historic centers of large cities where cooling demand is even higher
3.3.1. Heating habits because of the urban heat island effect.
Many buildings in the region are underheated due to energy
poverty – this is particularly true for detached houses in rural areas 3.4. Renovation actions
where specific heat losses are higher due to the high surface-to vol-
ume ratio; many of these buildings are inhabited by elderly people According to recently conducted studies [24,62] in the Czech
or those affected by fuel poverty. Underheating is dependent on Republic, about one third of the housing stock has been refurbished
climatic conditions as well – it is more typical to have only inter- so far. About 50% of large panel buildings, 75% of other multi-flat
mittent heating in several rooms in areas with a milder climate. buildings and approximately 60% of family houses have not been
Fully heated homes are typically heated to 18–20 ◦ C. Available sta- refurbished yet.
tistical data about the issue is insufficient in all countries, but there In Hungary, there are no official statistics on retrofit rates, but a
is available research on this specific topic, such as [33,79,68,40]. representative field survey has been carried out within the KEOP-
According to a field survey prepared for the national typology 7.9.0/12-2013-0019 project in 2015, selecting 2000 buildings to
in Serbia, only 50% of houses heat more than 50% of the living area, obtain a picture about the energy performance of the residential
which leads to the conclusion that even houses which are small in building stock. Regarding the building stock built before 1990, it
size or have a central heating system are forced to leave some space can be stated that for detached houses, 11.5% of the façade walls,
unheated. The daily heating regime in individual houses is difficult 9.2% of the attic slabs and 6.6% of the cellar ceilings have been
to estimate, but it can be stated that family houses in Serbia are retrofitted with thermal insulation and 19.6% of the windows have
typically underheated [33]. been changed. In multi-flat buildings (including large panel build-
Fuel poverty is also a very significant problem in Bulgaria, where ings), 10.6% of the façade walls, 3.6% of the attic slabs and 5.4% of the
most dwellings are underheated. Generally, only rooms occupied cellar ceilings have been retrofitted with added thermal insulation
during most of the day are heated [79]. and 26.9% of the windows have been changed. In large panel build-
Dwellings with district heating show a completely different pic- ings, 14.9% of the façade walls, 14.1% of the flat roofs and 10.1% of the
ture. Blocks of flats are usually heated to 21–22 ◦ C in the Czech cellar ceilings have been retrofitted with added thermal insulation
Republic, 22–24 ◦ C in Hungary, 20 ◦ C in Serbia, 18–19 ◦ C in Bulgaria. and 33.5% of the windows have been changed [40].
Partial heating is not typical, except for a part of the common rooms In the Czech Republic and Hungary, the most commonly applied
(corridors, staircases). In district heating, heating is turned off dur- energy saving measures are additional exterior wall insulation
ing the night from 10pm–6am on working days and 10pm–7am (polystyrene foam or, occasionally, mineral wool), the replacement
on weekends and holidays, 24-h heating is only provided under of windows and entrance doors, additional roof insulation and insu-
very specific circumstances. In large panel buildings with district lation of ceiling above basement, hydraulic balancing of the heating
heating, heat cost allocators are generally installed in Bulgaria [47]. system and controllable heating with heat cost allocation. In hous-
In the Czech Republic, both heat cost allocators and thermal regu- ing blocks, switching from exterior heat transfer stations to DH
lation valves are required by law in dwellings served by district substations inside the buildings is quite common. Building-level
heating [80,81]. In Hungary and particularly in Serbia, the lack heat metering is common. The replacement of heating and DHW
of heat cost allocators means that a significant portion of such sources with more efficient technologies can be observed especially
dwellings are overheated, wasting energy [40,82,83]. In Serbia, in family houses [24,40,75].
bad ventilation habits are frequently observed in collective hous- Recent renovations have been focused mainly on large panel
ing units during the heating season and low outside temperatures, buildings partly due to available subsidies and also for practical
especially long lasting ventilation with tilted windows and a fully reasons because these standardized buildings offer good opportu-
opened radiator valve [74,82,83]. nities for optimized solutions that can be used repeatedly. In the
Czech Republic, the refurbishment of apartment blocks and multi-
3.3.2. Cooling habits family buildings have been analyzed in the PanelScan study [84]
It is a general problem in the region that there are no statistics in 2009 and in two more recent, but less comprehensive studies
available about cooling in residential buildings. However, climatic [25,26]. The studies showed that many buildings were only par-
differences can be easily recognized – the need for cooling in the tially renovated (e.g. window replacement) and that the quality of
Czech Republic is relatively low, the majority of dwellings are not the work is rather varied – the same is true for Hungary as well
equipped with cooling or air conditioning devices. In Hungary, [40].
there are already a couple of very hot summer weeks, but cooling No official data is available on refurbishment actions and their
in residential buildings is still not dominant [40]. In Serbia, where results in Serbia. Large discrepancies exist between the refurbish-
the summer is even hotter (see cooling degree days in Section 3.1) ment rates of multifamily and single family housing. Although there
there are no official data on the percentage of occupied dwellings have been renovation activities in both types of buildings, these
with AC installed, but it is not insignificant. Data on cooling systems were not in any way organized or subsidized by the state, remain-
and habits in Bulgaria is unavailable as of the time of this writing. ing sporadic in nature. A survey [85] provided data about the status
Individual installations and portable equipment (wall mounted of retrofit levels: 16.3% of the buildings have exterior insulation
single reversible split units with EER = 2–3) are the most frequent with a typical thickness of 5 cm. Roof insulation exists in 11% of the
option in all countries and there are no significant differences buildings with an average thickness of 10 cm.
between single and multifamily housing types. The number of units The 2011 census in Bulgaria also included questions related to
per dwelling depends on the size of living area, commonly one unit energy efficiency, the results show that 16% of occupied dwellings
per household, cooling 1–2 rooms. In Bulgaria and Serbia, these have thermal insulation and 30% are fitted with energy efficient
appliances are often also used for heating, which is not the case windows [21]. Owners usually commit only to step-by-step partial
in Hungary [40,41,36]. Cooling systems in the housing sector are renovation, starting from windows and then applying insulation.

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Table 3
Building classes for the cross country comparison.

Building classes for the cross-country comparison Construction Abbreviation

period

Single family Single family houses, built before World War II –1944 SFH.1944
houses
Single family houses, built after World War II and before the end of the communist period 1945–1989 SFH.1945-89
Single family houses, built after the end of the communist period 1990– SFH.1990

Multi-flat buildings Multi-flat buildings, built before World War II –1944 MFH.1944
Multi-flat buildings, built after World War II and before the end of the communist period (except 1945–1989 MFH.1945-89
buildings built with industrialized technology)
Multi-flat buildings, built with industrialized technology (e.g. large panel block buildings) 1945–1989 IND.1945-89
Multi-flat buildings, built after the end of the communist period 1990– MFH.1990

Fig. 2. The energy need for heating of the building classes – existing state.

Complex renovations have only been carried out for a small num- the TABULA/EPISCOPE building type indicators using the national
ber of detached (investments by the owners) and multi-flat houses total floor area as the weight. The classes are defined according to
(50–60 buildings annually in the past years with EU or national the building size (single family house or multi flat building) and
grants). Apartment buildings made with industrialized technology construction period (before World War II; after World War II and
and multi-family buildings constructed before 1999 are prioritized before the end of the communist period; and after the end of the
for renovation. The housing fund in Bulgaria is relatively new, but communist period). The communist period ended in 1989 or 1990
due to ownership problems (almost 100% of the stock is privately in the analyzed countries. During the communist era, the industrial-
owned) the Bulgarian government decided to provide 100% funding ized building technology was heavily used in the Eastern countries
rate with limited resources for some industrialized technology and in order to decrease the general housing shortage, meriting a differ-
multi-family residential buildings, therefore, a notable increase is ent building type: large panel buildings (mostly using prefabricated
foreseen for the near future [42]. reinforced concrete sandwich panels).

4. Results 4.1. Energy need for heating

As explained in the methodology section the TABULA/EPISCOPE Fig. 2 shows the calculated energy need for heating of the build-
building types were grouped into 7 larger building classes (Table 3). ing classes for the current state. The average values of the building
The results for the 7 building classes are the weighted average of types are the weighted average of the countries using the total floor

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Fig. 3. The energy need for heating of the residential building stock – existing state.

area as the weight. The energy need for heating of single family water for multi flat buildings is mainly produced by electric water
houses built before World War II is between 180.0–335.1 kWh/m2 heaters in most of the countries, but in some cases district heating
per year, their weighted average is 283.73 kWh/m2 per year. or natural gas was considered.
Multi family buildings of the same period have lower energy Total primary energy demand results are shown on Fig. 4. Since
need because of their lower surface to volume ratio (between natural gas is the dominant heating energy carrier in Hungary
142.7–315.1 kWh/m2 , year) and thicker walls, yielding a weighted and the Czech Republic for SFH.1944 types, these have a higher
average of 219.63 kWh/m2 per year. The average single family primary energy demand than in Serbia and Bulgaria where the
house built between 1945 and 1989 needs 242.36 kWh/m2 per year, most common heating source for these types is wood (average:
while the ‘traditional’ multi flat buildings require 187.0 kWh/m2 438.8 kWh/m2 , year). The same characteristics can be observed in
per year and the large panel blocks 183.4 kWh/m2 per year. The case of SFH.1945-89 types (average: 337.35 kWh/m2 , year). The pri-
buildings built in the last two decades have significantly lower mary energy demand is significantly lower for newly built single
energy need (134.6–121.36 kWh/m2 , year). family houses (SFH.1990), the average figure is 224.65 kWh/m2 ,
The sizes of the residential building stocks in Bulgaria, Serbia, year.
Hungary and the Czech Republic are similar, the total floor areas of The main heating system in Serbia for MFH.1944 is individ-
the residential buildings are 284.9 – 289.6 – 317.7 – 336.8 million ual heating by electricity, therefore the primary energy demand
m2 in order (see Section 3). of this type is 65.2% higher than the average (393.2 kWh/m2 , year).
SFH 1945-89 building types have the highest total floor area Multi flat buildings built after World War II (MFH.1945-1989) are
in all countries (between 24.2% and 43.5% of the total floor area), mainly heated by district heating based on coal or natural gas in the
therefore, the energy need of these types is the most significant, Czech Republic and in 12 large cities in Bulgaria, while in Hungary,
see Fig. 3. only the buildings of industrialized technology (IND.1945-1989)
are heated by district heating. A significant portion of MFH.1945-
4.2. Total primary energy demand for heating and domestic hot 1989 buildings are heated by individual electrical heating in Serbia,
water resulting in high primary energy demand. Other building types
(e.g. IND.1945-1989) are heated by district heating. The average
Primary energy demand for heating and domestic hot water has primary energy demand of the ‘traditional multi flat buildings’
been calculated for each TABLE building type, taking into account (MFH.1945-1989) is 335.48 kWh/m2 , year and the “industrialized
the distribution of energy carriers and technical building systems. multifamily houses” (IND.1945-89) is 286.19 kWh/m2 , year. The
These values were then used to calculate the primary energy newly built multi flat buildings (MFH.1990) have a notably lower
demand for building classes using weighted averages. As explained primary energy demand (with an average of 204.48 kWh/m2 , year).
in Section 3.2.2, natural gas is dominant in Hungary and in the Czech The total primary energy demand for heating and domestic hot
Republic as opposed to Serbia and Bulgaria, where wood and elec- water of the residential building stock is the highest in the Czech
tricity are the prevailing energy sources for heating. Domestic hot Republic (448.3 PJ/year) and the lowest in Bulgaria among the ana-

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Fig. 4. Total primary energy demand for heating and domestic hot water of the building classes – existing state.

Fig. 5. The total primary energy demand for heating and domestic hot water of the residential building stock – existing state.

lyzed countries (see Fig. 5). The reasons for the differences are energy need figures reflect climatic differences and the fact that the
rather complex (climatic factors, energy sources, different distri- considered HDDs relate to an average indoor temperature of 20 ◦ C
bution of building types), but it can be easily seen that the heating except for Bulgaria, where the design value is 19 ◦ C [46,55,57–59].

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Table 4
The total primary energy demand for heating and domestic hot water of the residential building stock − existing state.

Total primary energy demand [PJ/year]

Groups of building types Hungary Bulgaria Serbia Czech Rep.

Single family house 310.6 122.5 190.2 297.5

Multi flat buildings 63.6 85.7 124.3 140.4
Large panel buildings 7.1 43.1 19.4 10.4
Total 381.3 251.3 333.8 448.3

Table 5
Country-specific U-values of the deep renovation scenario.

U-values [W/m2 K]

Building constructions Hungary Bulgaria Serbia Czech Republic

Old buildings before 1990 (buildings built with traditional technology)

Façade walls 0.17–0.21 0.27–0.35 0.14–0.18 0.12–0.25
Attic slab/roof 0.12–0.15 0.26–0.38 0.10–0.18 0.10–0.21
Windows 1.00 0.80 1.00 0.60–1.10

Buildings built with industrialized technology

Period 1967–1991 [36] 1962–1996 [46] 1960–1990 [53] 1957–1991 [28]
Façade walls 0.18–0.19 0.27 0.12–0.15 0.24–0.25
Attic slab/roof 0.12–0.15 0.27 0.12–0.15 0.14–0.15
Windows 1.00 0.80 1.00 0.80

New buildings (after 1990)

Façade walls 0.12–0.17 0.26 0.12–0.14 0.12–0.24
Attic slab/roof 0.10–0.14 0.15 0.11–0.14 0.10–0.16
Windows 1.00 0.80 1.00 0.60–0.80

Table 6
The U-values of the building envelope of the mid-rise industrialized apartment block built between 1945 and 1979 in Hungary (IND.1945-89 building class).

Elements of the building envelope Existing state Deep renovation (NZEB)

Structure U-value [W/m2 K] Structure U-value [W/m2 K]

Wall sandwich panel: reinforced concrete 0.80 additional 16 cm external insulation on 0.19
(15 cm); polystyrene insulation (8 cm); existing structure
reinforced concrete (7 cm)
Flat roof waterproofing; lightweight concrete 0.91 additional 24 cm insulation on top of 0.14
(10 cm); reinforced concrete (15 cm) existing structure
Cellar ceiling linoleum (0,5 cm); reinforced concrete 0.55 additional 20 cm insulation on the 0.15
(15 cm); polystyrene insulation (5 cm) underside of existing structure
Window double-pane wooden casement 3.30 new window with triple-glazing, low-e 1.00
windows coating and argon gas filling

Due to the high proportion of single family houses in the build- Table 7
The primary energy saving potential of the residential building stock in the analyzed
ing stock, those types are responsible for 48.7–81.4% of the total
countries.
primary energy demand of the building stock (see Table 4).
Building classes Hungary Bulgaria Serbia Czech Rep.

SFH.1944 71.2% 69.3% 69.3% 79.8%

SFH.1945-89 71.6% 66.5% 81.9% 74.6%
4.3. Energy saving potential SFH.1990 59.3% 66.0% 64.4% 54.1%
MFH.1944 60.4% 73.3% 81.7% 75.0%
The objective was to determine the energy saving potential MFH.1945-89 66.8% 73.3% 78.3% 68.7%
IND.1945-89 49.1% 73.7% 59.8% 47.3%
achievable with deep renovation targeting nearly zero building
MFH.1990 47.3% 69.0% 76.8% 64.4%
energy (NZEB) requirements. The selection of the refurbishment Residential building stock 67.8% 69.4% 77.2% 70.4%
measures was based on the characteristics of the analyzed countries
(Table 5).
The deep renovation concept is based on the extensive thermal
insulation of the building envelope, the replacement of old win- the circulation pump and thermostatic valves, solar collectors will
dows and doors together with the modernization of the heating be installed.
and DHW systems and installing renewable energy systems (e.g. The possible primary energy saving potential (Table 7) depends
solar collectors, heat pumps). on the proposed change of energy carriers: savings are lower for a
For example, the mid-rise industrialized apartment block built shift from prevailing wood logs to biomass, and higher for a shift
between 1945 and 1979 in Hungary (Table 6). Mostly built with from electricity to natural gas (or coal to natural gas). The change
basement and ground floor and 10 stories, with a flat roof and from electricity results in extremely high savings (e.g. in case of
heated by district heating. The external structure is reinforced con- MFH.1944 and SFH.1945-89 building classes in Serbia).
crete sandwich panel. The refurbishment aiming for nearly zero The primary energy saving potential in the analyzed countries
energy use will include extensive insulation for the building enve- is between 67.8% and 77.2% in the case of deep renovation to NZEB
lope, doors and windows will be changed (Table 6). In addition to requirements.

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5. Discussion and conclusions most up-to-date data, some of the data sources used in the calcula-
tions are several years old, such as [22,84,61,29,86]. In some cases,
In this paper, the housing stocks of four countries in Eastern there are more recent relevant data available, but at a lower level
Europe have been analyzed, highlighting the similarities and dif- of detail.
ferences in climate, housing stock, building shell, utilized energy The study described in the paper could be a starting point
sources, applied technical building systems and building usage. to develop policy actions. However, further analysis is needed in
Energy performance calculations have been carried out for heating the fields of investment and operation costs, state policy, fund-
and domestic hot water according to EN ISO 13790 and the EPBD ing system structures, stakeholders, macro-economic aspects, labor
rules using the TABLE calculation tool. impact and social acceptance. Further analysis of policy implica-
Slight climatic differences have been identified with an increas- tions, while important, are beyond the purposes and scope of the
ing number of heating degree days and decreasing cooling degree article.
days from Southeast (Bulgaria) to Northwest (Czech Republic). The A possible future research could include cooling that is particu-
major share in the energy balance belongs to heating as mechanical larly important in Serbia and Bulgaria. It would also be interesting
cooling systems still have a low, but increasing importance due to to extend the scope to other countries in the region with similar
fuel poverty, particularly in Bulgaria. building stocks like Poland, Slovakia, Romania, Baltic countries and
Single family houses have the greatest significance, both in their additional countries of the former Yugoslavia.
ubiquity and energy consumption. According to our calculations,
these building types are responsible for 48.7–81.4% of the total
Acknowledgements
primary energy demand of the housing stock, depending on the
country.
This paper is published as a result of participation in
Large panel buildings constitute a special building class in the
the EPISCOPE research project (Energy Performance Indicator
region. The district heating networks supplying these buildings are
Tracking Schemes for the Continuous Optimization of Refurbish-
partly obsolete, partly modernized. They are generally prioritized
ment Processes in European Housing Stocks), with co-funding
in energy efficiency interventions due to the suitability of uniform
from the ‘Intelligent Energy—Europe’ Programme, contract No.
solutions and the resulting cost efficiency.
IEE/12/695/SI2.644739.
Applying thermal insulation to the building envelope has
Results for Serbia were partly developed within the SLED project
become typical in new buildings only in the last 5–15 years (a
funded by the Austrian Development Agency (ADA) and imple-
small majority of the housing stock). The energy performance of
mented by the Regional Environmental Center for CEE.
the housing stock is therefore determined by the old stock and the
Field surveys for Hungary were carried out within the KEOP-
renovations already carried out. The share of already retrofitted
7.9.0/12-2013-0019 project.
buildings is moderate in Hungary, Serbia and Bulgaria: mainly par-
tial renovation actions have been carried out so far in a minority of
the dwellings. The situation is slightly better in the Czech Republic References
due to the systematic subsidy actions in the last two decades. Com-
[1] EPBD, Directive 2010/31/EU of the European Parliament and of the Council of
plex renovations are still not the norm, although it is a priority in
19 May 2010 on the energy performance of buildings, Off. J. Eur. Union.
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