Analysis of Residential Buildings in Poland for Potential Energy Renovation toward Zero-Emission Construction

Abstract

The aim of the study was to identify the state of residential buildings in terms of energy consumption and modernisation in Poland against the background of the EU, and to determine factors and activities increasing households′ interest in net-zero energy buildings. In the European Union, we are observing a tendency to increase the energy efficiency of buildings, including residential, and decarbonise building stock by 2050. The objective of the undertaken activities is to reduce energy use and the negative impacts of the use of buildings on the environment. Attaining this objective requires modernising many buildings. This dissertation includes an investigation into the condition of buildings in Poland from the aspect of energy use and the kind of carriers of this energy, and also into another issue: what factors and activities may increase society′s interest in net-zero energy buildings, and in the use of energy from renewable sources in residential buildings. The studies were conducted with the use of the data provided by the Central Statistical Office and EUROSTAT, and also of the reports of the European Commission, the data of the Central Emission Register of Buildings (CERB) and the Odysse–Mure database. An important source of information was also surveys conducted with the application of CAWI (Computer-Assisted Web Interview), and also of PAPI (Paper and Pencil Interview), among 387 households in Poland. For the purpose of analysing the results of the studies, the methods of descriptive statistics, the chi-square test of independence, the ANOVA test of Kruskal–Wallis and the Mann–Whitney U-test were used. The analysis gives rise to the conclusion that, in residential buildings, household′s annual primary energy demand is dependent on the year in which a building was commissioned. Newer buildings can boast smaller heat energy use. Simultaneously, ever more households are undertaking activities that will result in the thermal modernisation of residential buildings. The studies have shown that the development of net-zero energy buildings requires undertaking activities in the scope of introducing allowances and subsidies, and also increasing social awareness in the scope of this kind of building. Interest in buildings using solely renewable energy sources is contributed to by raising energy prices, and also the falling prices of required installations.

1. Introduction

Climate change is seen as one of the greatest global challenges important for the future of Europe and the entire world. According to the report “Future of Europe”, 45% of Europeans adhere to the view that environmental problems and climate changes are global problems, which the EU ought to tackle [1]. As a response to the climate crisis and intensive processes connected with environmental degradation, the EU has devised a development strategy known as the European Green Deal (EGD), the principal objective of which is to transform Europe into a climate-neutral area [2]. In accordance with the relevant EU regulation, all 27 member states have committed themselves to undertake activities owing to which the emission of greenhouse gases will have been reduced by 55% by 2050 in comparison with their levels in 1990. It is assumed that, by 2050, Europe is to have become a climate-neutral continent [3]. It is worth indicating that the same objective is being pursued by other countries (such as Japan and South Korea) as well [4,5]. In turn, China has made a similar pledge, stating 2060 as a deadline [6].

In accordance with the European Green Deal, the society of the EU is to become fair, affluent and climate-neutral, with a modern, resource-efficient and environment-friendly economy [2]. The assumptions of the EGD, therefore, influence all the areas of the economy in the environmental, economic and social dimensions alike. Of the sectors impacting the global environment, the construction industry has been defined as one that may significantly contribute to reducing greenhouse gas emissions [7,8,9]. As the relevant studies show, public utility buildings and residential ones as well use enormous quantities of energy. In the EU, the construction industry uses 40% of the total energy, and is responsible for 36% of greenhouse gas emissions [9].

In connection with the fact that the construction industry is responsible for much of the CO₂ emission into the environment, it has become necessary to analyze the energy use of all buildings. Currently, the objective of building designers is to improve energy efficiency, and also to use energy from renewable sources [9,10,11,12]. Increased interest in nearly net-zero energy buildings (NZEB) is observable worldwide [13,14,15,16,17,18]. According to the definition in Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings, net-zero energy buildings have a very high energy performance, with nearly zero or very low required energy to be derived from renewable sources [3,19,20]. Net-zero energy buildings play, therefore, a crucial role in decarbonising the economy, understood as activities the objective of which is to methodically reduce CO₂ emission into the atmosphere [18]. Taking that under consideration, it comes as no surprise that the EU construction industry has seen important and expensive investments, connected with drawing up the principles and rules of designing net-zero energy buildings, modernising buildings already commissioned, and also developing informational campaigns addressing society [9,21,22,23,24,25]. This is the reason why the European Parliament has proposed that new public utility facilities be net-zero-emission as soon as 2027, and, by 2030, that all new buildings be the same [9]. It is worth indicating that the countries of the EU can adopt individual approaches to implementing the strategy in question, and, as a result, they develop their own action strategies [21,23]. Owing to identifying climate areas, technical conditions applicable to buildings, areas of the largest energy use, and also analysing users′ behaviours, it has become possible to develop individual references and procedures, the principal objective of which is to improve building designs, change user behaviour, and also increase the production of renewable energy [11,12,26,27].

In connection with the significance of the presented issues, it was the principal objective of our study to investigate the state of residential buildings in terms of energy consumption and modernization in Poland against the background of the EU, and also to determine the factors and activities increasing households′ interest in net-zero energy buildings. Upon the basis of a literature review, the authors arrived at the conclusion that there is still not enough literature relevant to studying the population′s awareness of and opinions on the necessity of reducing energy use in residential buildings. An increase in society′s awareness relevant to NZEB may significantly contribute to reducing greenhouse gas emissions, and also introduce activities increasing the decarbonisation of residential buildings. Therefore, this dissertation is an attempt to answer the following questions:

• What is the condition of buildings in Poland in the aspect of energy use depending on the kind of energy carriers?
• What factors and activities may increase society′s interest in net-zero energy buildings?
• What is the scale of using energy from renewable sources in residential buildings?

On the basis of the review of the literature and studies conducted hitherto, three research hypotheses were formulated in this dissertation.

Hypothesis 1 (H1).

Providing a household with RES installation diversifies the state of modernizing residential buildings.

Hypothesis 2 (H2).

The most important activity encouraging the choice of net-zero energy buildings is financial support for households in the scope of such investments.

Hypothesis 3 (H3).

Raising the prices of energy from conventional sources increases the use of energy from renewable sources.

2. Literature Review

2.1. Climate and Energy Policy of Poland on the EU Background

One of the milestones in the development of the European Union’s energy policy was the adoption of the so-called energy and climate package 3 × 20 by the European Council in 2007. Three main goals were set therein [28]:

• − a 20% reduction in greenhouse emissions compared to 1990;
• − an increase of up to 20% in the RES’s share of the total EU energy consumption;
• − an increase of up to 20% in energy efficiency.

The regulations adopted in 2009 as part of this package set binding obligations for Member States in the area of energy and climate, but EU policy has changed in subsequent years. The EU climate and energy policy in the 2030 perspective framework was defined by the European Commission on 22 January 2014 [29]. The new goals proposed at that time concerned:

• − a 40% reduction in greenhouse gas emissions compared to the 1990 base year;
• − an increase of up to 27% in RES’s share in the total EU energy consumption;
• − an increase of up to 27% in energy efficiency;
• − completion of an integrated, internal energy market.

The highlighted goals were again subjected to changes in 2018, although the most important ones concerned increases in the RES share from 27% up to 32%, and increases in energy efficiency from 27% up to 32.5% [30]. Those ambitious plans and their implementation in the adopted time perspective was perceived as difficult, yet further changes and climate and Energy policy tightening were proposed.

The “Clean energy for all Europeans” regulatory package, on which work was undertaken in the EU forum, was completed in 2019. This indicates the manner of operationalization of the EU climate and energy goals for 2030, and contributes to the implementation of the energy union and the construction of a single EU energy market [31]. Under the agreed arrangements, EU countries were obliged to develop national plans for energy and climate (NECP) by the end of 2019. In the same year, the European Commission published a communication on the European Green Deal—a strategy whose goal is for the EU to achieve climate neutrality by 2050 [32]. As part of the European Green Deal, in September 2020 the European Commission proposed to increase the target level of reducing greenhouse gas emissions, taking into account emissions and removals, to at least 55% by 2030 compared to the 1990 level. Its purpose is to “transform the EU into a fair and prosperous society, with a modern, resource-efficient and competitive economy where there are no net emissions of greenhouse gases in 2050 and where economic growth is decoupled from resource use” [33].

Currently, as part of the “Fit for 55” package [34], the EU is working on changing the regulations on climate, energy and transport, adapting the existing law to the goals for 2030 and 2050, which include achieving the goals of reducing net greenhouse gas emissions by at least 55% in 2030 and climate neutrality in 2050.

The high energy efficiency and decarbonisation of building resources in each Member State by 2050 are to be ensured by the Directive on the Energy Performance of Buildings (2010/31/EU) [3], amended in 2018 (2018/844/EU) [20], along with the Directive on Energy Efficiency (2018/2002/EU) [35]. The revised Energy Performance of Buildings Directive (2018/844/EU) [20] introduced long-term renovation strategies:

−

Each Member State must establish a long-term strategy of renovation, providing support towards the renovation of domestic buildings, in both public and private sectors in order to ensure the high energy efficiency and low emissions of building resources up to 2050;

−

Enhancement of transformation of existing buildings into nearly-zero-energy-consuming ones up to 2050, and since 2021, all newly erected buildings have had to be characterised as nearly-zero-energy-consuming;

−

Supporting the modernisation of all buildings in terms of smart technologies.

In Poland, the energy policy until 2020 was regulated by the following:

−

The Energy Policy of Poland until 2030 [36];

−

National Action Plans (KPD) concerning Energy efficiency [37,38,39,40] KPD from 2007, 2012, 2014, and 2017, respectively, the development of which was required by the directives 2006/32/WE [37] and 2012/27/UE [38].

These documents were consistent with the assumptions of the EU policy and assumed:

−

The improvement of energy efficiency, the security of fuel and energy supplies, and the development of RES, including biofuels;

−

The development of competitive fuel and energy markets and a reduction in the impact of the energy sector on the environment.

Considering the longer term, the energy policy of Poland is defined by strategic framework documents, such as:

−

Energy Policy of Poland until 2040 [39];

−

National Energy and Climate Plan for 2021–2030 [40];

−

Long-term building renovation strategy [41].

The “Energy Policy of Poland until 2040” adopted in 2021 provides for, among others:

−

The implementation of nuclear power in 2033;

−

A reduction in greenhouse emissions of 30% by 2030;

−

An increase in energy efficiency by 23% by 2030 compared to the 2007 primary energy consumption forecasts.

According to the adopted policy, coal is to account for no more than 56% of electricity generation in 2030, and no more than 28% in 2040.

In order to properly shape the energy policy, all buildings in Poland, both public and private, were reviewed. There are 14.2 million buildings in the country, of which almost 40% are single-family residential buildings. A significant part of the them are buildings with low energy efficiency, requiring thermal modernisation. Therefore, a Long-Term Building Renovation Strategy was adopted. According to the document, 7.5 million thermomodernisation investments are to be made. This strategy also assumes an average annual rate of thermal modernisation at the level of about 3.8%, assuming that by 2050, 65% of buildings will achieve am EP indicator (unit demand for primary energy) no higher than 50 kWh/m² year.

The plan recommended in the strategy assumes quick growth with slight thermal modernisation, with the gradual dissemination of deep, more comprehensive thermal modernisation by 2030. Shallow thermomodernisation consists primarily of the replacement of high-emission heat sources, such as coal-fired boilers, with ecological devices. Such action is currently undertaken primarily under the “Clean Air” program [42]. Because of those changes, an improvement in air quality in Poland is ensured. On the other hand, deep thermomodernisation is connected to the necessity of undertaking additional actions, such as insulating a house, replacing windows or installing another heat source [43].

2.2. Factors Affecting Energy Consumption in Residential Buildings

Residential buildings require energy both in the form of heat (for instance, for preparing hot utility water, heating and cooling premises) and power needed to light premises or operate electrical appliances [44].

The use of energy in households depends on many factors, including their age. The majority of buildings (85% of buildings in the EU) were built prior to 2001. Many of them need fossil fuels for heating and cooling, and also rely on old technologies and energy-inefficient appliances [45]. What matters as well is that it is in these very buildings that people are not affluent enough to afford to conduct major repairs. Currently, the energy renovation indicator for buildings in the EU is low and amounts to merely 1%. According to the estimations of the European Commission, this value ought to reach 3% to attain the EU′s objectives in the scope of energy efficiency and climate. It indicates that it is necessary to double the efforts of the countries of the EU to implement the renovation strategy of 2020 [7].

Another factor influencing energy use is the location of a building. In Poland, there are, for instance, five climate zones, in which several tens of weather monitoring stations are situated. These zones may have local microclimates, in which windiness, the amount of received sunlight, and also average temperatures are frequently different than those in other regions [46]. Prior to making a decision relevant to investment, therefore, it is worth paying attention to the dominating climate in the planned building site so as to be able to make a timely decision concerning certain architectural and construction solutions [16].

The amount and kind of energy used in residential buildings are also dependent on the building size, architectural design, and energy supply systems in use. To provide an example, using high-quality insulation is indispensable to reducing energy demand. In turn, using floor heating instead of heaters may reduce energy use because heating water to very high temperatures is not necessary for ensuring thermal comfort [47]. What matters as well is that small flats need less energy because their floor space is smaller [10].

The rising population, and also improved quality of life, are further factors influencing energy demand. Flats in developed countries tend to use more energy than in emerging economies, which results, first and foremost, from the number of appliances in use, which significantly contribute to the users′ comfort in households [10,13,16].

Taking into consideration the development of technology, and also the increased interior comfort demand in recent decades, it is possible to arrive at the conclusion that this trend in energy demand in residential buildings will not only remain visible, but may even become more noticeable, in the future [10].

When setting energy performance requirements for technical building systems, EU Member States should use, where available and appropriate, harmonized instruments, in particular testing and calculation methods and energy efficiency classes. This type of construction assumes the use of design and technological solutions that will save energy spent on heating the entire building, as well as domestic water, using such indicators as EP (kWh/m²), concerning annual demand for non-renewable primary energy, and U (W/m²K), concerning heat escaping from the house to the outside (this refers to the thermal insulation of walls, windows, doors, roofs and ceilings). These indicators are subject to substantial changes due to attempts to meet conditions set by The Paris Agreement and 2050 Climate Neutral Europe [48].

2.3. Net-Zero Energy Buildings-Concept

Because of constant fears connected with limited energy supplies, shrinking energy resources, rising costs, and also an ever greater influence of greenhouse gases on climate, we may notice constantly growing interest in net-zero-energy building [49,50,51]. To the development of this concept, the EU and national legislation, the constant development of modern technologies, raising society′s environmental awareness, and providing favourable conditions for RES micro installations are conducive [52].

In the literature, it is possible to find many variants of “net-zero”; among others, we see net-zero-energy building, net-zero-energy cost building, net-zero-energy emissions building, nearly net-zero-energy building, zero-emission building, zero-carbon building, or net-zero-exergy building [53,54], whereas there is still no standardised approach to designing this type of building [47]. As was rightly indicated by W. Wu, and also by H. M. Skye, each and every one of the stakeholders in NZEB pays attention to different aspects. Buildings designers seek to maintain compliance with energy laws, and they focus principally on energy derived from local sources. In times of raising energy prices, the priority of buildings′ users is, in turn, energy costs. The governments of particular countries are mostly concerned with energy supply. In turn, “green” organisations are principally interested in the problem of pollution emissions into the environment related to energy use. Nevertheless, however, all the variants of “net-zero” have three common features: combining NZEB with power supply infrastructure, reducing NZEB energy demand (by using energy-efficient technologies), and also using (in NZEB) renewable sources of energy [12].

NZEBs are significantly different from the standard, ones both in the aspect of used construction technologies and the methods of acquiring and using energy [7,10,12]. Construction materials and state-of-the art technologies are applied in construction projects, allowing one to reduce energy use; moreover, the entire supply of produced renewable energy is used [54]. The most popular systems using such energy may be enumerated as follows: PV panels, solar collectors, heat pump systems, wind turbines and systems using biomass [8,12,13,14,16,47]. While looking at architectural and construction solutions, the following aspects require consideration as well: a compact building shape (the smaller the shape co-efficient (A/V) is, the smaller heat losses are), thermal barriers (ensuring a permanent barrier for air and humidity), and also the orientation of a building (for instance, in the northern hemisphere, it ought to be N–S, because in the summer direct exposure to sun light is smaller and that limits the need for cooling, while in the winter a greater exposure to the sun reduces the need to heat a building). Moreover, windows ought to be able to let in as much sunlight as possible, and roofs can keep a building cool inside (preventing, ipso facto, solar panels from becoming hotter). In turn, ventilation systems ought to provide fresh air and reduce energy losses. In the literature on the subject, it is also recommended to ensure combining NZEB with a conventional energy source, which guarantees comfort in households if renewable energy does not meet the requirements of an end user. Moreover, if there is a surplus of energy being generated, it may be “handed over” into the network, which allows for the maintenance of a building′s internal energy stability [55].

There are many assets of NZEBs, including: reducing maintenance costs, becoming self-sufficient in terms of energy sources, minimising the negative impact on the environment, and also creating a good internal microclimate (owing to a constant temperature, and also the inflow of fresh air into a building). Another asset is reducing major repair costs due to using more reliable systems, and also the state of the art and best materials, which allow for the better protection of a building from weather factors. Moreover, NZEB is perceived as more valuable than conventional ones, which means that the price of the former has grown a lot, making their sale more profitable [47,54,55].

In spite of their numerous assets, NZEBs have certain possible faults, which need considering prior to making a final investment decision. First of all, what matters is the high costs of solar collectors, PV systems or ground source heat pumps. Another problem may be that of acquiring professional building staff, which are still not easily found on the market as far as designers and engineers able to construct NZEBs are concerned. Another possible threat is the fact that NZEBs’ ability to react to future possible rises or falls in the temperature of their surroundings may be a major challenge in times of ever more noticeable global warming [54].

To recapitulate, it may be concluded that NZBEs have a significant influence on the economy. Various configurations of them are available in the market and are compliant with various climate and construction regulations. All the stakeholders of the NZEB strategy ought, therefore, to choose technologies and elements compatible with the local conditions and limitations.

3. Methodology

This research work included the initial analysis of the literature relevant to the construction industry, with particular attention being paid to published dissertations connected with studying the population’s awareness and opinions on the factors and activities that increase interest in NZEB.

Due to these facts, an attempt was made to investigate the energy efficiency of residential buildings in Poland as set against the background of the EU, and also determine factors and activities increasing households’ interest in net-zero energy building. The studies were conducted in two stages.

In the course of the first stage, the data from the Central Statistical Office [56] and EUROSTAT [57] were used together with the reports of the European Commission [58,59], the data of the Central Emission Register of Buildings (CERB) [60] and the Odysse-Mure database [61]. The second stage involved the analysis of surveys conducted with the use of CAWI (Computer-Assisted Web Interview), and also PAPI (Paper and Pencil Interview) [62], among 387 households in Poland. The sample was selected using the snowball method to reach as many households as possible. The proper survey had been preceded by pilot studies, after which a survey questionnaire was sent to several tens of people living in the studied households, who were also requested to find more participants for the study; simultaneously, a link to the survey was located on various forums. The study was conducted from August to September 2022 all over Poland.

The questions in the survey were relevant to modernising activities undertaken for the latest 5 years, activities increasing society’s interest in net-zero energy building, factors increasing interest in a building reliant solely on renewable energy sources, and declaring whether the residential building in question had ever undergone an energy audit determining the degree of its energy efficiency. In the question concerning residential buildings modernisation, respondents were able to point out many possible answers. In terms of activities that would affect the interest in zero-emission construction and factors encouraging investment in construction using only RES, the respondents were asked to rank the analysed factors/actions in order from 1 to 4, where 1 was the least important component and 4 was the most important.

The survey questionnaire also included a personal data section, in which the respondents were asked about their address of residence, age, sex, average disposable monthly income [63], and also type of building (one-family—including semi-detached and terraced houses—or a multi-family one) [64,65] and the location of a building in a given region NUTS 1 [66]. The survey was entirely anonymous. Depending on the nature of the variables, the following methods were used to analyse the results:

• Percentage distribution presentation (in the form of tables or figures) of nominal or ordinal characteristics, also of summary descriptive statistics for numerical characteristics [67];
• Chi-square test of independence (to assess the correlation of qualitative traits) [68]. Among the many statistical approaches used for observational studies, the Chi-square (χ²) test is widely used by researchers studying survey response data. It helps in analyzing differences in categorical variables (nominal in nature). The Chi-square test of independence was used to verify the relationship between (1) the state of the residential building and RES installation, and (2) the place of residence, age, gender and residential building, and the energy audit conducted for a residential building;
• The Mann–Whitney U-test (to determine the correlations between qualitative and quantitative traits when there were two categories of a qualitative variable) [69,70]. This test was used to verify the relationship between gender and residential building and (1) the assessment of the activities that increasing interest in net-zero energy buildings, as well as (2) the assessment of the factors encouraging investment in buildings using only renewable energy sources;
• The ANOVA Kruskal–Wallis test was used to determine the correlations between qualitative and quantitative traits when there were more than two categories of a qualitative variable [71,72,73,74,75]. The Kruskal–Wallis test was used to verify the relationship between place of residence, age and NUTS 1 macroregion, and assess (1) the activities increasing interest in net-zero energy buildings (2) and factors encouraging investment in buildings using only renewable energy sources.

The study was conducted assuming a level of significance of α = 0.05 [68,76]. The following levels were assumed:

p < 0.05—significant statistical correlation;

p < 0.01—highly significant statistical correlation;

p < 0.001—very highly significant statistical correlation.

4. Presentation of Research Results

4.1. Profile of Residential Buildings in Poland

In order to determine the profiles of residential buildings in Poland, the data of the Central Statistical Office (CIS) for 2020 relevant to energy use in households were taken under consideration. As is shown by these data, more than half of residential buildings in Poland in 2020 (54.95%) were multi-family ones (Figure 1). One-family detached houses constituted 39.36%, and one-family terraced houses comprised 5.60% of all residential buildings. Only 0.09% were buildings of different kinds.

Most buildings in Poland (31.77%) date back to the period 1961–1980, whereas one in every five (20.21%) to the years 1981–1995 (Figure 2). Prior to 1946, 18.06% of all buildings had been erected, whereas the period 1996–2011 saw the construction of 12.11% of all buildings. In the years 1946–1960, 10.69% of all residential buildings were erected, whereas 7.16% of buildings were erected after 2011. These data indicate that the majority of buildings in Poland (92.84%) date back to the period before 2011, in connection with which a large part of the existing building stock will soon require renovation or reconstruction.

Simultaneously, it needs to be highlighted that the situation in the scope of the thermal insulation of residential buildings in Poland has improved in recent years (Figure 3). In 2016, such buildings comprised 60.10%, whereas in 2020 they constituted nearly 70% of residential buildings. Simultaneously, the share of uninsulated buildings in the residential building stock shrunk from 26.90% in 2016 to 21.86% in 2020.

The thermal insulation of a building influences the thermal energy use in a household (Figure 4). In 2020, network heat use was lower by 0.01 GJ/m² in thermally insulated buildings in comparison with those not thermally insulated. Much greater differences were seen between both kinds of building in the scope of gas use (0.28 GJ/m² vs. 0.36 GJ/m²) and also black coal use (0.90 GJ/m² vs. 1.00 GJ/m²).

4.2. Structure of Energy Use in Households in Poland against the EU Background

The structure of energy use in households is of major importance for developing activities the objective of which is to improve the energy efficiency of buildings. Energy use in residential buildings is principally connected with heating premises, preparing hot water, making meals, and also lighting and using electrical appliances. The data from the Odysse–Mure database were used to assess the structure of final energy use in households in the countries of the EU.

On the basis of these data, it may be concluded that more than 60% of energy use in households results from heating. In recent years, the percentage of the energy use for that purpose has been reduced. In 2013 in Poland, heating consumed 68.72% of total energy used, whereas in 2019 this value was 63.07%. Similar tendencies are seen in the EU, although their scope is smaller. In 2013 in the EU, energy use for the purpose of heating constituted 66.61%, whereas in 2019, it was 63.57%. The analysis of the data, moreover, gives rise to the opinion that Polish households use more energy for the purpose of heating water, and also preparing food, and less on lighting and using electrical appliances (Figure 5).

4.3. Structure of Energy Use in Households Is Dependent on the Kind of Energy Carriers

In order to achieve, by 2050, neutrality in CO₂ emission, it is indispensable to investigate the structure of energy use in households depending on the kinds of energy carriers. As is shown by the data in Figure 6, this structure is dominated in the entire territory of the EU by natural gas (31.81%), which is likely caused by the fact that it is seen in the EU as a low-emission energy source. In turn, sunlight constitutes 24.72% and biofuels 16.77% of the structure of energy use.

Households in Poland meet their needs to a far greater degree using solid fossil fuels (24.64%), and also primary solid biofuels (23.00%) (Figure 6).

Phasing out fossil fuels therefore constitutes a major challenge to the Polish economy and Polish households, which are connected not only to the natural resources at our disposal but also to household infrastructure (boilers) as well, which need fossil fuels as the basic condition of being commissioned at all (one instance is coal). The scale of this phenomenon is presented by the data acquired from the declarations submitted to the Central Emission Register of Buildings, giving rise to the belief that, in terms of energy structure, Polish households use nearly twelve times more solid fossil fuels compared to the EU (24.64% vs. 2.71%), and also two times less power (12.23% vs. 24.72%) and gas (18.20% vs. 31.81%).

4.4. Analysis of the Statistical Data of the Central Emission Register of Buildings

In order to gather information on the sources of low-emission heat in buildings in a standardized, cohesive way, at various levels of public administration all over the country, the project “Integrated system of reducing low emission (ISORLE)” is implemented in Poland by the Chief Building Inspectorate under in the Operational Programme ‘Digital Poland’; Priority Axis: E-administration and Open Government; Activity 2.1: High Accessibility and Quality of Public Services. This project consists in implementing an IT system that will gather building data and make them available. In connection with that, each and every owner/administrator of a building (residential and non-residential) in which there is a source of heat is obliged to submit a declaration to the Central Emission Register of Buildings (CERB), this being a system in which comprehensive information relevant to the sources of heat in buildings can be found. The reason for setting up the CERB was to improve air quality, and to combat smog. The above declarations were submitted before 30 June 2022, and applied to the sources commissioned before 1 July 2022. For installations commissioned after 1 July 2022, the deadline for submitting the declaration is 14 days from the date of putting the heat source into operation. There are two categories of declarations: one is relevant to a source/sources of heat and the use of fuels in residential buildings (declaration A), and the other is relevant to a source/sources of heat and the use of fuels in non-residential ones (declaration B). As part of this paper, an analysis of the data obtained from registrations using declaration A was conducted. It needs to be indicated that, of the 6,406,760 declarations submitted for residential buildings, half of the households (3,205,630) use solid fuels in boilers.

As is shown by the data presented in Figure 7a, more than half of the boilers operated in residential buildings whose owners/administrators have submitted a declarations do not meet the requirements (or may not meet them, because there is no suitable information on them). Simultaneously, in accordance with the PN-EN 303-5:2021 standard [77], 47.53% of boilers belong to the following classes: 3, 4 and 5. The presented data also give rise to the conclusion that only 1.92% of boilers are Eco-design ones, and these are recommended by the European Parliament in the scope of power and emission requirements for solid fuels [58,78].

Among solid fuels in use, the most commonly used is coal and coal-derived fuels (54.64%). This influences the emissions of CO₂ and air quality. In turn, 38.49% of all devices use wood in pieces (Figure 7b).

The declarations of the owners/administrators of residential buildings give rise to the conclusion that boilers using a solid fuel constitute 35.45% of all sources of heat. In 24.60% of the declarations, the following heat sources were referred to: gas boiler, flow-through gas heater or gas fireplace. Every tenth owner/administrator of a building heats their premises using a fireplace, “goat” stove or solid fuel–air heater. In 10% of the declarations, power heating or electric boilers were indicated as sources of heat. Other sources of heat in Polish residential buildings include: kitchen shafts, stove kitchens or coal kitchens (5.66%), tile stoves using solid fuel (4.70%), solar collectors (3.39%), urban or local heat network or system heat (2.60%), heat pumps (2.19%), and oil boilers (0.80%) (Figure 8).

5. Results of the Survey

5.1. Identifying the State of Residential Buildings in Light of Empirical Research

The detailed profile of the sample is presented in

Table 1. Sample characteristics.

Variable	N	%
Place of residence
village	127	32.82
city with up to 50,000 residents	80	20.67
city with over 50,000 up to 100,000 residents	46	11.89
city with over 100,000 up to 500 thousand residents	65	16.80
city with over 500,000 residents	69	17.83
Age
2001–present (Generation Z)	8	2.07
1982–2000 (Generation Y)	283	73.13
1961–1981 (Generation X)	82	21.19
1943–1960 (Baby boomers (BB))	14	3.62
Gender
Female	207	53.49
Male	180	46.51
Average monthly disposable income per person in a household *
<PLN 1000	14	3.62
PLN 1000.01–1500	36	9.30
PLN 1500.01–2000	46	11.89
PLN 2000.01–2500	54	13.950
PLN 2500.01–3000	72	18.60
>PLN 3000.01	165	42.64
Residential building
single-family building	219	56.59
multi-family building	168	43.41
NUTS 1 macroregion
eastern	113	29.20
south-west	99	25.58
south	58	14.99
Mazovian province	39	10.08
northwest	25	6.46
north	36	9.30
central	17	4.39

* EUR 1 = PLN 4.7133 (Polish Zloty) on 1 September 2022.

.

The data give rise to the conclusion that 26.87% of the respondents have devices that use renewable energy sources, the most common of which are PV panels (77.88%) and solar collectors (25.96%). On the other hand, 28.80% of respondents pointed to the use of heat pumps in residential buildings, i.e., installations that obtain energy from the natural environment and, using part of the electricity, process heat for the needs of central heating and hot water installations. Simultaneously, installations using renewable energy sources are much more frequent in single-family houses (43.38% vs. 5.40%) and also in the countryside (48.00%). A statistically significant relationship between the presence of renewable energy installations and the type of building was confirmed on the basis of the Chi-square test of independence (p = 0.0000).

In the studied group, 45.99% declared that their residential building had been modernised. In turn, 27.13% of the respondents indicated that such activities were not indispensable (Figure 9).

In connection with this, the respondents were requested to indicate the modernisation works conducted in the last 5 years [79] (Figure 10). The data give rise to the conclusion that the modernisation works undertaken in the buildings most frequently included external thermal insulation (51.69%), replacing or modernising heating systems (48.88%), and also replacing external doors (34.27%). One-quarter of the conducted modernisation works involved the thermal insulation of remaining barriers (26.40%), and also replacing window frames (25.84%).

Of the buildings of people declaring the possession of RES installations, 61.54% were modernised, and 32.69% did not require such activities (Figure 11). The scope of modernisation in the residential buildings of people not possessing such installations was smaller. In this group, 44.9% of the studied group declared that modernisation had been conducted, whereas 25.01% claimed it was not needed. In turn, 30.04% of the respondents indicated that their buildings had not been modernised. The Chi-square test of independence was used to assess the relationships between these variables. The conducted analyses show that providing systems using renewable energy sources for households is related to modernising residential buildings (p = 0.0000). On this basis, it is possible to arrive at the conclusion that the first hypothesis was confirmed.

5.2. Investigating Activities Increasing Interest in Net-Zero Energy Buildings, and also Factors Making Households Willing to Invest Solely in Renewable Energy Sourcers

5.2.1. Activities Increasing Interest in Net-Zero Energy Buildings

Bearing in mind that 26.87% of residential buildings in the studied group had not been modernized, an attempt was made to investigate the opinions of people living in the studied households on the scope of activities that would increase interest in net-zero energy buildings (

Table 2. Structure of the assessments of activities increasing interest in net-zero energy buildings.

Assessment of Activities *	Increase in Society′s Awareness	Subsidies and Allowances	Simplifying Building Regulations	Legal Requirements
1	18.86%	3.62%	15.76%	61.76%
2	32.56%	11.37%	40.05%	16.02%
3	21.45%	37.47%	29.72%	11.37%
4	27.13%	47.55%	14.47%	10.85%
Total	100%	100%	100%	100%

* 1—least important activities, 4—most important activities.

, and also Figure 12).

The studied individuals indicated that the most important activity encouraging society’s interest in net-zero-energy buildings is financial support for such investments (mean: 3.29). The second indicated factor was, in the opinion of the respondents, an increase in social awareness (mean: 2.57), but in that case, opinions differed more (Figure 12). Legal regulations that make it mandatory to erect only net-zero-emission buildings were assessed by the respondents as the factor that is least effective in terms of encouraging the choice of this kind of building (mean: 1.71). The results of the research confirm, therefore, the second hypothesis, indicating the significance of financial support for investment in net-zero-energy buildings.

The assessment of the activities increasing interest in net-zero-energy buildings was diverse and dependent on the sex of the respondents. A statistically significant relationship between these variables was confirmed on the basis of the Mann–Whitney U test. The males more favourably assessed activities aimed at making construction-related legal regulations simpler (mean assessment: 2.53 vs. 2.34) (p = 0.0307). This was different for the legal requirements that make it mandatory to choose a net-zero-energy building. The females assessed this factor significantly more favourably than the males did (average assessment: 1.81 vs. 1.60) (p = 0.0496) (Figure 13).

5.2.2. Factors Encouraging Households to Invest in Renewable Energy Sources

Raising energy prices is the most crucial factor encouraging households to invest in renewable energy sources. Exactly 38.76% of those studied assessed this factor as the most important, and 41.86% of them said it was very important. Similar assessments were seen in the case of falling prices of installations using RES. More than half of the studies said this factor was the most important (

Table 3. Structure of assessments of factors encouraging users to invest in buildings using solely renewable energy sources.

Assessment of Factor *	Raising Energy Prices	Concern about Climate	Poor Air Quality	Decrease in the Prices of RES Installations
1	10.08%	33.85%	36.43%	19.64%
2	9.30%	36.69 %	48.32%	5.68%
3	41.86%	23.00%	10.85%	24.29%
4	38.76%	6.46%	4.39%	50.39%
Total	100.00%	100.00%	100.00%	100.00%

* 1—the least important factor, 4—the most important factor.

). On this basis, the third hypothesis was confirmed. The development of investments in renewable energy sources determines the raising prices of energy from conventional sources.

The analysis results are confirmed by collating the mean assessments of particular factors (Figure 14). It needs to be indicated that there are differences in the respondents′ opinions. The raising energy prices (mean: 3.09), were rated higher than the decrease in the price of RES installations (mean: 3.05). Simultaneously, the factor that least effectively encourages users to invest in buildings using only renewable energy sources is poor air quality (mean: 1.83). The assessment of this factor was the least diversified (Figure 14).

The ANOVA Kruskal–Wallis test was used to assess the incentives to invest in buildings with renewable energy sources. The analysis showed that two factors influenced users’ decisions to invest in buildings using only renewable energy sources. Statistically significant factors included the place of residence (p = 0.0109) and air quality (p = 0.0151). (Figure 15).

As the urban population rises, the assessment of the importance of raising energy prices as a factor encouraging investment changes, and this factor is seen as less and less important. In the case of cities with a population not exceeding 50,000, the mean of the assessments amounts to 3.34, and in the case of those with a population above 500,000, it amounts to 2.80. Simultaneously, an opposite trend is seen in the case of the assessment of the importance of poor air quality. For the respondents from the largest cities, this is a more important factor than for those from small cities and villages (mean: 2.10 vs. 1.73) (Figure 15).

Having conducted an energy audit and assessed the energy efficiency of a building was confirmed by 12.91% of the respondents. In turn, 48.06% of the respondents indicated that such activities had not taken place; 39.02% of respondents did not know (Figure 16).

6. Discussion

The global energy crisis, and also the war in Ukraine, have made it necessary to use renewable energy sources in order to become independent of the uncertain and unstable Russian fossil fuel markets [80]. Renewable energy sources such as wind energy [81], solar energy [82], hydroelectric energy [83], the energy of oceans [84], geothermal energy [85], biomass and biofuels [86,87,88] are an alternative to coal, petroleum and natural gas, ipso facto contributing to increases in energy self-sufficiency, and also limiting greenhouse gas emissions. The EU is one of the pioneers in promoting decarbonisation and using renewable energy [44]; in 2004, the use of energy derived from renewable sources in the EU amounted to merely 9.6%, whereas in 2020, it reached 37%. What is noticeable as well is a decrease in fossil fuel energy use. In 2005, this value amounted to 61%, whereas by 2020 it had fallen to 42% [27,88]. A large part of the energy derived from fossil fuels is still indispensable for residential buildings.

The energy transformation requires increasing the participation of RESs and improving the energy efficiency of buildings (households). Because new buildings put into use each year account for only 2% of all buildings in Poland, a significant improvement in the country’s energy balance and a reduction in expenditure on the use of facilities is possible only by improving the energy efficiency of buildings. However, planned investments must make financial sense for households.

The studies conducted by Adamczyk and Dylewski concerning the fairly advanced thermal modernization approaches of one-family houses (modernization or exchanging heat sources, accompanied by exchanging window frames/doors or the thermal insulation of facades) yielded a lack of financial benefits for house owners [89]. The analyses conducted by Gołąbska confirmed that erecting a house using solely RESs is much less cost-efficient than a traditional house [90,91,92,93]. However, the studies of other authors show that it is profitable to invest in RESs [82,94,95].

According to Makvandia and Safiuddin, the most important activity encouraging investment in net-zero-energy buildings is the state′s financial support [96]. Simultaneously, lower prices of RES installations encourage people to invest in such solutions [96], which is confirmed by other studies as well [97,98,99,100,101]. As such, the state′s role is very important, as it involves implementing support programs dedicated to households deciding to invest in RESs [102,103,104,105,106].

In the years 2014–2019, approximately PLN 7.6 billion was invested in the thermal modernization of residential buildings supported by public policy tools. In the years 2014–2018, virtually all the support was received by multi-family buildings, whereas in 2019, nearly 80% of the recipients were one-family houses, resulting from the thermal modernization allowance enacted at that time, and also the first effects of the “Clean Air” Program [92].

The long-term building modernization strategy [92] assumes that the total investment expenditure for renovating buildings in the years 2021–2050 (in the scope of thermal modernization and exchanging heat sources) will amount to, approximately, PLN 1.54 billion; in the years 2021–2030, this expenditure will amount to approximately PLN 400 billion, of which 3/4 will be spent on residential buildings [92].

7. Conclusions

The construction industry is the principal energy user worldwide. Erecting net-zero-energy buildings is, therefore, one of the strategies of decarbonisation, made possible by the scale of reducing energy offered by such buildings. In Poland, heating households consumes more than 60% of the total energy used for all purposes, and this energy is principally produced by burning coal in boilers (most of which are low-class devices). Such a situation means that striving to achieve the level of net-zero-energy buildings is a major challenge to the Polish economy.

Most of the buildings in use in Poland are not energy-efficient, and rely on fossil fuels; 92.84% of all residential buildings date back to the times prior to 2011, which renders it necessary to take steps to modernize existing building stock, as thermally-insulated buildings require less energy. The studies give rise to the conclusion that buildings whose residents declared to use RESs are modernized to a greater degree and newer because 27,13% do not require modernisation.

The studies also showed that the most important step that would increase interest in zero-energy buildings would be financial support for relevant investments, and also raising society’s interest. Implementing programs that consider subsidies for the modernization of buildings, and also provide them with RES installations, is of crucial significance from the point of view of making Poland a climate-neutral country.

Raising conventional energy prices is both an opportunity and a threat in terms of making a decision regarding investing in RESs. On the other hand, they constitute a stimulus to make investments in RESs; on the other hand, however, growing market uncertainty connected with the supply of energy may render the population even more pessimistic and reluctant to make decisions.

The factor most strongly encouraging investment in RESs, especially in cities, is poor air quality. The assessment of air quality showed a growing trend as larger and larger urban populations were studied. This means that, in large cities, in which air pollution is a problem, people are aware of the possible benefits of RESs. Different trends have been observed in relation to air quality and raising energy prices.

The studied group of households only included 26.87% of the respondents who confirmed using RES installations, which implies the need to further investment in RESs because their implementation will contribute to reducing greenhouse gas emissions. In this scope, it is necessary to launch programs supporting households in implementing low-emission solutions. Another important direction of action is conducting social campaigns to make people aware of climate change, and also encouraging them to take action to reduce using fossil fuel energy.

The conducted studies (theoretical and empirical) do not exhaust the subject of this dissertation. However, they indicate that it is necessary to undertake further studies, including the analysis of available solutions in the scope of net-zero-energy buildings in terms of their cost-efficiency and effectiveness. It is also important to develop the support for investments in RESs. The objective ought to be to propose the most effective solutions from the point of greenhouse gas emissions, and also reduce the costs of implementing such investments in households.