The Protection of Cultural Heritage in Poland in the Process of Enhancing the Energy Performance of Historic Buildings: An Analysis of Recent Strategic Policy Documents of the European Union and Poland (2005–2025)

Abstract

Over the past two decades, cultural heritage protection and the improvement of energy efficiency in historic buildings have become parallel yet frequently conflicting priorities of public policy. This paper analyses the contemporary strategic directions of the European Union and Poland between 2005 and 2025 with regard to the modernisation of historic buildings, within the broader framework of energy and climate transition. This study involves a comprehensive analysis of legal and strategic documents and national conservation guidelines, evaluating their impact on heritage protection practices. The research employs desk research and comparative analysis, as well as a preliminary empirical component based on indicators W1–W12. These indicators reveal a significant modernisation gap: only 0.3–0.5% of heritage buildings in Poland have undergone energy retrofitting, indicating low implementation of EU strategies. The study’s findings confirm the necessity of developing a coherent policy model that integrates the requirements of the Energy Performance of Buildings Directive with national conservation law, as well as harmonised assessment tools, such as energy and conservation audits. In conclusion, the implementation of ‘heritage-inclusive renovation strategies’ is required—respect the character, materiality, and authenticity of heritage buildings, while recognising their social and cultural significance.

1. Introduction

The concepts of cultural heritage and historic buildings form the basis for the analysis of the modernisation of heritage assets within the framework of energy transition strategies. In both Polish and European law, this terminology is of significant practical importance, insofar as it defines the scope of protection, the competences of the relevant authorities, and the interpretation of legal provisions concerning construction interventions in protected buildings.

At the European Union level, the notion of cultural heritage is not defined in a single, harmonised statutory manner; rather, it is articulated through strategic frameworks and recommendations. In accordance with Article 3.3. of the Treaty on European Union (TEU) [1], the EU is committed to the preservation and enhancement of Europe’s rich cultural and linguistic diversity. In a similar vein, the European Cultural Convention (1954) and the Faro Convention (2005) emphasise the social, identity-related, and educational significance of heritage, drawing attention to both its tangible and intangible aspects [2,3].

In practice, policy instruments such as the New EU Strategy on Adaptation to Climate Change (2021) [4], the Renovation Wave (2020) [5], and successive revisions of the Energy Performance of Buildings Directive (EPBD) acknowledge the necessity of protecting heritage buildings within the energy modernisation process, despite the absence of a uniform legal definition of a “historic building” in EU law. Instead, directives generally employ functional descriptions such as “buildings officially protected as part of a designated environment or because of their special architectural or historical merit” (EPBD Recast 2018/844/EU, Art. 2a) [6].

The flexibility of the wording in question enables Member States to interpret and apply the exemption to a variety of categories of heritage assets. However, this flexibility also creates inconsistencies in implementation, as evidenced by the fact that some states extend protection to a broad range of historic structures, while others restrict it to officially listed monuments.

In the Polish legal system, the concepts of cultural heritage and monument are clearly defined in the Act of 23 July 2003 on the Protection and Care of Monuments (Ustawa z dnia 23 lipca 2003 r. o ochronie zabytków i opiece nad zabytkami) According to Article 3, points 1 and 2, a monument is:

“An immovable or movable object, or a group thereof, being a work of human activity or related to human action, constituting evidence of a bygone era or event, the preservation of which is in the public interest due to its historical, artistic, or scientific value”

[7]

Cultural heritage in turn encompasses the entirety of heritage resources—both tangible and intangible—constituting part of national and European identity.

The Act also introduces the notion of a historic building, referring to any immovable property entered in the register of monuments or listed in the official records of heritage assets. In practice, this means that any form of construction activity—from maintenance and renovation to energy retrofitting or adaptive reuse—falls under a special legal regime requiring the approval of heritage protection authorities (Articles 36 and 37 of the aforementioned Act) [7].

This strict regulatory framework ensures the safeguarding of historical fabric but also poses challenges for integrating energy efficiency improvements within the limits of conservation law, highlighting the need for balanced, interdisciplinary approaches to renovation policy.

The modernisation of heritage buildings in Poland has given rise to a complex research problem arising from the need to reconcile the preservation of cultural heritage with the requirements of energy efficiency and climate neutrality. The challenge lies in maintaining the authenticity and aesthetic integrity of historic structures while reducing their energy consumption and carbon footprint. In a significant number of protected buildings, conventional energy retrofit measures–such as external insulation or complete replacement of joinery–are either technically unfeasible or prohibited by conservation regulations.

In this context, heritage-compatible modernisation strategies have become crucial, including the use of highly vapour-permeable internal insulation, modernisation of heating and ventilation systems, installation of heat pumps, integration of renewable energy technologies (photovoltaics, solar collectors, geothermal systems), and improvement of airtightness and thermal performance of historic windows and doors. The integration of Building Management Systems (BMS) has become increasingly prevalent in heritage buildings, with the objective of facilitating intelligent control and optimisation of energy utilisation.

These actions are in alignment with the priorities of the European Union’s energy and climate policy (including the European Green Deal [8], Fit for 55 Package [9], Renovation Wave Strategy, and EPBD Recast 2024), as well as with national frameworks such as the Polish National Energy and Climate Plan (KPEiK, 2019) and the Energy Policy of Poland until 2040 (PEP2040) [10,11]. Concurrently, they are obligated to adhere to the National Programme for the Protection and Care of Monuments (2023–2026) and the directives of the General Conservator of Monuments. Consequently, an analysis of the implementation of energy retrofits in historic buildings offers insight into two main areas. Firstly, it provides an understanding of the technical and environmental effectiveness of the applied solutions. Secondly, it explores the interaction between energy and heritage policies, and the creation of sustainable models of preservation and adaptive reuse that result.

2. Materials and Methods

The research was based on a comparative analysis of strategic documents of the European Union and Poland concerning the energy efficiency of buildings and the protection of cultural heritage, covering the period 2005–2025. The selection of this timeframe was guided by two premises:

• In 2005, Poland, as a new member of the European Union, became obligated to implement EU energy and climate regulations;
• The year 2025 marks the planning horizon for current national and EU strategies and policy frameworks in the field of building renovation.

2.1. Source Materials

The analysis encompassed the following groups of sources:

• EU-funded research and demonstration projects on heritage energy efficiency: Climate for Culture [12], EFFESUS—Energy Efficiency for EU Historic Districts’ Sustainability [13], RIBuild—Robust Internal Thermal Insulation of Historic Buildings [14], Protection of Cultural Heritage Objects with Multifunctional Advanced Materials (Nano-Heritage, 282992) [15], Climate2Preserv [16];
• EU legal and strategic acts: the New EU Strategy on Adaptation to Climate Change [4], Renovation Wave [5], Energy Performance of Buildings Directive (EPBD) [6], Energy Efficiency Directive (EED) [17], European Green Deal [8], and the New European Bauhaus Initiative [18];
• Polish strategic documents: The Energy Policy of Poland until 2030 and 2040 (Polityka Energetyczna Polski do 2030 roku (PEP2030) [19], Polityka Energetyczna Polski do 2040 roku (PEP2040) [11]), the National Energy and Climate Plan (Krajowy plan na rzecz Energii i Klimatu na lata 2021–2030 (KPEiK 2019)) [10], Long-Term Building Renovation Strategy (Długoterminowa Strategia Renowacji Budynków (DSRB 2022)) [20], National Energy Efficiency Action Plan (Krajowy Plan Działań dotyczący efektywności energetycznej (KPDEE 2017)) [21], the National Programme for the Protection of Monuments (Krajowy Program Ochrony Zabytków (KPOZ)) [22], and the Guidelines of the General Conservator of Monuments (Wytyczne Generalnego Konserwatora Zabytków (WGKZt, WGKZf)) (2020) [23,24];
• Scientific and institutional literature: Academic articles and critical studies on the thermal modernisation of historic buildings, climate adaptation, and sustainable renovation methods; institutional reports from the National Heritage Board of Poland (Narodowy Instytut Dziedzictwa (NID)), the Supreme Audit Office (Najwyższa Izba Kontroli (NIK)), and reports of the European Commission and non-governmental organisations such as Europa Nostra.

2.2. Classification Criteria

The analysed documents were classified according to the following criteria:

• Level of regulation: European vs. national;
• Nature of the document: legally binding acts (directives, laws, resolutions) vs. soft-law strategic or advisory documents;
• Scope of impact on heritage: general regulations (applicable to all buildings) vs. heritage-specific measures;
• Implementation instruments: financial programmes, operational plans, and conservation guidelines.

2.3. Analytical Methodology

The study was conducted in three main stages:

• Critical content analysis—identifying provisions addressing heritage protection, energy efficiency, and their interrelations;
• Comparative analysis—juxtaposing EU and Polish strategic documents in tabular form, examining objectives, interconnections, and implementation mechanisms;
• Case studies—analysing selected examples of good and poor practices from Poland and other EU Member States (e.g., adaptive reuse projects implemented under the Renovation Wave and the effects of Poland’s Clean Air Programme (Program Czyste Powietrze) [25].

2.4. Research Approach and Limitations

The adopted methodology is primarily desk research, involving the systematic analysis of existing materials—including strategic documents, legal acts, institutional reports, and scientific literature. This approach allows for the identification of trends, inconsistencies, and gaps in current policies and enables an assessment of their impact on cultural heritage protection in the context of energy performance improvement.

The analysis followed both qualitative and comparative principles, enabling the identification of differences between EU and national approaches and the recognition of points where conservation and energy objectives collide.

Complementarily, the source criticism method was applied to assess the coherence, timeliness, and effectiveness of the analysed acts and guidelines. Particular attention was given to discrepancies between declared policy intentions and actual implementation outcomes. Documents were categorised according to their influence on heritage modernisation processes and their regulatory scope (strategic, operational, or legal).

The research is grounded in the assumption that public policies on energy and heritage protection operate systemically, and their effectiveness can be evaluated through an analysis of interrelations and hierarchies among documents. Accordingly, EU and national strategies were compared in terms of consistency, complementarity, and potential conflicts in implementation.

A subsequent research phase will include a quantitative empirical component based on data from:

• The National Heritage Board of Poland (NID)—number of heritage buildings subject to renovation and modernisation;
• The General Conservator of Monuments (Generalny Konserwator Zabytków (GKZ))—number of conservations preservation permits and recommendations issued for energy retrofitting projects;
• The National Fund for Environmental Protection and Water Management (Narodowy Fundusz Ochrony Środowiska i Gospodarki Wodnej (NFOŚiGW))—data on projects financed under programmes such as Clean Air (Czyste Powietrze), Thermomodernisation Plus (Termomodernizacja Plus), and other initiatives supporting energy performance improvement.

These datasets will be cross-referenced with EU-funded projects (Horizon 2020, LIFE, Interreg, European Green Deal) to determine the actual scale of energy modernisation of heritage buildings in Poland (2015–2025) and to compare national and European trends.

The empirical analysis will include the calculation of indicators W1–W12 (

Table 1. Empirical Indicators for Analysing Energy Retrofits of Heritage Buildings in Poland (2015–2025). Author: Agnieszka Rek-Lipczyńska, Izabela Kozłowska.

Indicator Code	Indicator Name	Description and Calculation Method	Data Source (Public)	Type of Analysis
W1	Number of immovable monuments	Total number of properties listed in the Register of Immovable Monuments in a given year (or as of the end of the 2015–2025 period).	National Heritage Board of Poland (NID)—Open Data (otwartedane.nid.pl) [26]	Reference stock analysis
W2	Number of conservation interventions	Number of decisions issued by Regional Monument Conservators regarding works on monuments (repairs, conservation, modernisation).	Public Information Bulletins (BIP) of Regional Monument Conservators [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42]	Analysis of conservation activity
W3	Number of projects financed with public funds	Number of modernisation or renovation projects concerning heritage buildings co-financed by EU funds, NFOŚiGW, or the Ministry of Culture and National Heritage (MKiDN).	mapadotacji.gov.pl [43]; MKiDN [44]; NFOŚiGW [45]	Financial analysis
W4	Share of energy-related projects in total conservation interventions	(Number of projects with an energy-efficiency component/total number of conservation projects) × 100%	MKiDN [44]; NFOŚiGW [45]; BIP WKZ [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42]	Structural analysis
W5	Average value of financial support for energy projects	Average amount of funding for projects including energy-efficiency improvements in heritage buildings.	NFOŚiGW [45]; mapadotacji.gov.pl [43]	Economic analysis
W6	Share of voivodeships with high thermomodernisation intensity	(Number of Clean Air programme applications/number of monuments in the voivodeship) × 1000	NFOŚiGW [45]; NID [26]	Spatial density analysis (heat map)
W7	Ratio of programme applications to conservation decisions	(Number of Clean Air programme applications/number of WKZ decisions)—an indicator of potential interventions conducted without conservation supervision.	NFOŚiGW [45]; BIP WKZ [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42]	Conservation risk analysis
W8	Dynamics of MKiDN funding for heritage protection	Year-to-year change in the total amount of conservation grants during the 2015–2025 period.	MKiDN (otwartedane.gov.pl) [44]	Trend analysis
W9	Number of energy performance certificates for pre-1945 buildings	Number of historic buildings registered in the CHEB database (GUNB), disaggregated by voivodeship.	GUNB—CHEB Register [46]	Comparative analysis of energy performance
W10	Share of renovation projects using modern low-impact technologies (e.g., thin-film coatings)	Number of projects employing minimally invasive technologies to improve energy efficiency (based on project descriptions in the funding database).	mapadotacji.gov.pl [43]; technical reports—MKiDN	Qualitative innovation analysis
W11	Ratio of monuments to energy retrofit projects (modernisation penetration index)	(Number of monuments subjected to energy modernisation/total number of monuments) × 100%	NFOŚiGW [45]; NID [26]; MKiDN [44]	Estimation based on public databases (mapadotacji.gov.pl, MKiDN, NFOŚiGW); requires further verification of projects’ “energy component.”
W12	Regional conservation–energy conflict coefficient	(Number of energy projects implemented without WKZ approval/total number of energy projects) × 100%	NFOŚiGW [45]; BIP WKZ [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42]	Conflict and compliance analysis

), allowing for the evaluation of spatial, financial, and institutional dynamics of energy retrofitting in Polish heritage buildings. These indicators will also help identify potential policy conflicts between energy objectives and the protection of cultural heritage values.

The limitations of the study primarily stem from the limited availability of empirical data. In Poland, there is no central monitoring system dedicated to tracking the thermomodernisation of heritage buildings, which makes it difficult to precisely estimate the scale of such interventions. Public statistics (e.g., NFOŚiGW [45], Statistics Poland—GUS [47]) do not differentiate between heritage buildings and the general building stock. Furthermore, institutional data are frequently dispersed across multiple authorities and may not span the entire research period in a consistent manner.

An additional limitation arises from the dynamic nature of the legal and strategic framework. Frequent updates to both EU and national policies (e.g., successive revisions of the Energy Performance of Buildings Directive (EPBD), or new versions of national renovation strategies) necessitate the continuous updating of analytical findings.

In view of the aforementioned factors, the conclusions presented in this article should be regarded as provisional and open to future refinement, as new empirical data and sectoral statistics become available.

The methodological framework of this study combines qualitative and quantitative approaches, integrating document-based research, content analysis, and comparative evaluation of national and EU-level strategic policies. The empirical dimension is predicated on the evaluation of a selected set of performance indicators (W1–W12), which are derived from national datasets and official reports. However, it is imperative to exercise caution when interpreting these indicators, given the limitations associated with data availability, update frequency, and the heterogeneity of reporting standards across institutions. The values presented herein represent relative measures of alignment and intensity rather than statistically representative data.

All datasets used in this study are open-access and verifiable:

• The National Heritage Board of Poland (Narodowy Instytut Dziedzictwa (NID))—open database of protected monuments and conservation programmes;
• The Ministry of Culture and National Heritage (Ministerstwo Kultury i Dziedzictwa Narodowego (MKiDN))—publicly accessible policy and legal documents through the ISAP and Dziennik Ustaw systems;
• The National Fund for Environmental Protection and Water Management (Narodowy Fundusz Ochrony Środowiska i Gospodarki Wodnej (NFOŚiGW)—open database of funded energy-efficiency projects and climate programmes;
• Supplementary EU-level data were obtained from EUR-Lex, Eurostat, and European Commission policy databases.

To enhance transparency, Figure 1 presents a simplified block diagram of the analytical workflow, illustrating the three main research stages:

• Stage 1. The classification of strategic documents (EU, national, regional) according to thematic relevance (A. Heritage protection; B. Energy efficiency; C. Sustainable development);
• Stage 2. The qualitative content analysis using predefined categories and coding schemes (C1–C5) reflecting regulatory and implementation dimensions;
• Stage 3. The quantitative synthesis through comparative scoring of indicators (W1–W12), followed by critical interpretation in relation to the identified policy gaps.

This multi-layered framework allows for both contextual understanding and empirical comparison, while acknowledging the methodological constraints arising from the diversity of available data sources.

3. EU-Funded Research and Demonstration Projects on the Energy Efficiency of Historic Buildings

Over the past two decades, the European Union has supported numerous research and demonstration projects aimed at improving the energy performance of historic buildings while safeguarding their cultural, architectural, and material integrity. These initiatives have provided the empirical and methodological foundation for current European and national policy frameworks, including the Energy Performance of Buildings Directive (EPBD), the Renovation Wave Strategy, and the European Green Deal.

The following section reviews and critically discusses several key EU-funded projects—Climate for Culture, EFFESUS, RIBuild, Protection of Cultural Heritage Objects with Multifunctional Advanced Materials (HEROMAT/Nano-Heritage), and Climate2Preserv—that have significantly contributed to shaping the state of research and practice in this field. Each of these projects represents a distinct but complementary approach: from risk and resilience assessment to integrated district-level decision tools and technical validation of retrofit solutions. Together, they illustrate how interdisciplinary collaboration and experimental validation have advanced the balance between heritage conservation and energy efficiency across Europe.

3.1. Climate for Culture (CfC)

The project focused on assessing the risk of damage to heritage in a changing climate (scenario modelling, risk maps, guidelines for limiting damage to buildings and collections) [12]:

• Key contribution: combination of climate projections with indoor environment and material risk parameters; strong scientific foundation, broad consortium;
• Limitations: emphasis on risk and adaptation (climatic conditions, microclimate management) rather than hard indicators of energy efficiency improvements at the building level;
• Policy relevance: support for EU adaptation policies and heritage resource resilience strategies.

3.2. EFFESUS—Energy Efficiency for EU Historic Districts’ Sustainability

The main outcome of this project was the development of a methodology for selecting energy interventions compatible with heritage values and a Decision Support System (DSS), verified in case studies in seven historic districts (most of which are on the UNESCO list) [13]:

• Advantage: transfer of assessment from individual buildings to urban complexes, integration of technical, energy and conservation criteria;
• Limitations: DSS requires local calibration (data on resources, climate, management practices), and the comparability of results between cities is sometimes limited by contextual differences;
• Policy relevance: direct support for the Renovation Wave and EPBD (planning the sequence of interventions in the historic fabric).

3.3. RIBuild—Robust Internal Thermal Insulation of Historic Buildings

The project developed guidelines for the selection and design of internal insulation in historic buildings, with particular emphasis on moisture risk (hygrothermal models, damage assessment sheets, data collection tools) [14]:

• Advantage: strong operationalisation of condensation and degradation risks for internal insulation solutions, which translates into practical design decisions;
• Limitations: recommendations require accurate material data and in situ verification; transfer to buildings with unusual structures may be limited;
• Policy relevance: substantive support for the implementation of the EPBD and national standards for protected buildings.

3.4. Protection of Cultural Heritage Objects with Multifunctional Advanced Materials (Nano-Heritage HEROMAT)

The project resulted in the development of advanced, environmentally friendly protective materials (coatings, composites) for heritage buildings [15]:

• Advantage: material progress (functional surfaces with protective properties) that can indirectly support the durability of building envelope elements in energy modernisation projects;
• Limitations: emphasis on material protection rather than energy balance; need for long-term in situ ageing assessment;
• Policy relevance: synergy with EU policy on safe and sustainable building materials (SSbD) and energy-efficient conservation.

3.5. Climate2Preserv

As part of the initiative, decision-making protocols for cultural institutions were developed, enabling a review of energy reduction strategies taking into account the requirements of collections, buildings and systems (training, tools, exchange of best practices) [16]:

• Advantage: pragmatic, process-oriented nature (how to make decisions within real constraints);
• Limitations: stronger roots in the museum/institutional sector than in historic residential buildings;
• Policy relevance: support for the implementation of energy saving and adaptation plans in the cultural sector, consistent with the Green Deal and efficiency targets.

3.6. A Critical Synthesis of Projects

Three methodological approaches relevant to current EU policy on historic buildings emerge from the projects listed above:

• The assessment of risk and resilience (Climate for Culture)– adaptation tools and risk mapping for heritage;
• Integrated Intervention Planning (EFFESUS)—multi-criteria DSS for historic districts, combining energy efficiency with conservation values;
• The technical validation of critical solutions (RIBuild, HEROMAT materials)—procedures for assessing internal insulation and material durability, minimising the risk of damage.

The empirical and methodological projects presented above regarding current EU data on historic buildings (EPBD, Renovation Wave, Adaptation Strategy).

3.7. Current Global Validation of the HAM Models (Heat, Air and Humidity)

In order to enhance the credibility of technical analyses (e.g., for internal insulation), it is recommended that the latest benchmarks and validations of heat-air-moisture (HAM) models be referred to:

• Dang, Janssen and Roels provide a comprehensive benchmark dataset for validating HAM models of building components (data and verification protocols) [48];
• Dang et al. conducted a multi-centre, empirical round-robin validation of HAM models. The objective of this study was to assess the robustness and reliability of these models in predicting 1D hygrothermal response [49].

The significance of this works lies in the fact that it supports the replicability and comparability of research, which is crucial when transferring the results of EU projects into national practice and standards.

4. Results

This section presents the main analytical findings of the study, structured around four thematic axes: the coherence of national and EU strategies, gaps in institutional integration, examples of innovative technical solutions, and opportunities for bridging conservation and sustainability goals. Each subsection draws on empirical indicators and case-based insights to support critical interpretation.

4.1. European Union Strategic Documents on Improving the Energy Performance of Buildings (Since 2005)

Within the European Union, the issue of building energy efficiency has, since 2005, been shaped primarily by climate and energy packages and a series of directives that define minimum performance standards. Initially, the matter of historic and heritage buildings appeared only marginally—often as exemptions from strict efficiency requirements, justified by the need to preserve their cultural and architectural value. For instance, the EPBD permitted Member States to exclude heritage buildings from minimum energy performance obligations in order to avoid imposing technical solutions that could compromise their authenticity or material integrity.

Over time, however, the EU recognised that almost 20% of the European building stock constructed before 1945 demonstrates low energy efficiency, representing a considerable potential for energy savings. Consequently, the most recent EU strategies—particularly those formulated under the European Green Deal—increasingly emphasise the integration of climate policy goals with cultural heritage protection, promoting sustainable renovation methods that balance conservation with innovation.

As part of the comparative analysis, this study identified a set of key EU policy documents that directly or indirectly address the relationship between energy efficiency improvements and heritage protection. The compilation covers legislative and strategic instruments from 2010 to 2021, which collectively shape the framework of the EU’s climate and energy policy.

The following table provides a concise overview of each document, specifying the issuing institution and the main assumptions related to both cultural heritage and energy performance (

Table 2. Overview of selected EU documents (post-2005) concerning the energy efficiency of buildings and cultural heritage. Author: Agnieszka Rek-Lipczyńska.

Document (Year)	Issuing Body	Main Assumptions Regarding Cultural Heritage and/or Energy Efficiency
Directive 2010/31/EU on the Energy Performance of Buildings (EPBD Recast, 2010) [6]	European Parliament and Council of the EU	Established minimum energy efficiency requirements for buildings. Allowed Member States to exempt heritage buildings from these obligations (Art. 4(2a)) to preserve their architectural and historical value. Introduced energy performance certificates, excluding protected monuments.
Directive 2012/27/EU on Energy Efficiency (EED, 2012) [50]	European Parliament and Council of the EU	Set binding energy-saving targets, including the obligation to renovate 3% of central government buildings annually. Allowed exemptions for historically valuable buildings (Art. 5(2)), recognising the need to respect their specific character.
Directive (EU) 2018/844 amending EPBD and EED (2018) [51]	European Parliament and Council of the EU	Introduced long-term renovation strategies (up to 2050) covering the entire building stock, including heritage buildings. Emphasised “deep renovation” towards nearly zero-energy buildings (nZEB) while preserving historic value and authenticity.
European Green Deal (2019) [8]	European Commission	Comprehensive EU strategy for achieving climate neutrality by 2050. Envisioned a large-scale building renovation initiative (Renovation Wave). Initially focused on energy transition and job creation, with cultural heritage integrated later through initiatives such as the New European Bauhaus.
Renovation Wave—Communication COM (2020) 662 (2020) [5]	European Commission	Aimed to double the renovation rate across the EU and remove investment barriers (~35 million renovations by 2030). Recognised the need for specific approaches to historic buildings and encouraged the exchange of best practices and the use of traditional, sustainable materials.
New EU Strategy on Adaptation to Climate Change (2021) [4]	European Commission	Focused on enhancing climate resilience of infrastructure and communities. Cultural heritage was mentioned only marginally, with general references to the need to protect valuable assets from climate impacts. No specific instruments were introduced.
New European Bauhaus Initiative (2020–2021) [18]	European Commission	A cultural and design initiative complementing the Green Deal, promoting the fusion of aesthetics, sustainability, and inclusiveness in the built environment. Encouraged innovative renovation of heritage buildings by combining energy efficiency with preservation of historic character (e.g., adaptive reuse with ecological materials).

).

In the analysis of the reviewed documents, attention was drawn to the evolution of the European Union’s approach to historic buildings—from initial exemptions (EPBD 2010, EED 2012), through their gradual inclusion in long-term renovation planning (EPBD 2018), to the integration of cultural and aesthetic dimensions within the initiatives of the European Green Deal and the New European Bauhaus.

The results of this review form the basis for a subsequent comparative analysis with national policy documents.

Initially, under the provisions of Directive 2002/91/EC [52] and its subsequent revision, Directive 2010/31/EU (EPBD Recast) [6], historic buildings were exempted from the obligation to meet minimum energy performance requirements (Article 4(2a)) and from the obligation to obtain energy performance certificates. This decision, associated with the EU’s “20-20-20” climate package, sought to safeguard the authentic architectural fabric of heritage buildings from inappropriate thermal retrofitting measures that could potentially compromise their historical and aesthetic value.

In practice, however, as noted by numerous studies, such a complete exemption of heritage buildings from energy policies contributed to the marginalisation of energy efficiency issues in the heritage sector [53,54,55,56,57,58,59,60,61]. Many historically valuable structures across the Member States were left outside any energy-saving standards, widening the gap between conservation policy and sustainable development objectives. Critics argue that this approach represented a missed opportunity to reduce energy consumption and emissions in the historic building stock.

Over time, EU policy began to evolve toward a more balanced and sustainable model, one that does not exclude heritage buildings from modernisation processes but instead encourages their adaptation with respect for cultural values. A turning point came with Directive (EU) 2018/844, which for the first time explicitly included historic buildings within long-term renovation strategies extending to 2050 [51].

Subsequent documents—such as the European Green Deal (2019) [8], the Renovation Wave (2020) [5], and the New European Bauhaus (2021) [18]—increasingly emphasise the cultural and aesthetic dimensions of the built environment, recognising architectural heritage as an integral part of the climate transition Announced by the European Commission as a “co-creation project”, the New European Bauhaus (NEB) initiative was linked to the Horizon Europe programme and the EU cohesion policy, serving not as a legislative act but as a platform for knowledge exchange and best practices.

The outcomes of NEB include awards for exemplary projects, including heritage renovations, and the establishment of a network of contact points supporting transnational cooperation. The initiative significantly increased awareness that heritage can serve as a resource in the green transformation, inspiring numerous revitalization projects of historic and post-industrial spaces aligned with sustainability principles. In Poland, examples include adaptive reuse of industrial heritage and the renewal of historic housing estates identified as “NEB lighthouses.” Nonetheless, critics point out that NEB remains a soft-policy framework, and its long-term success depends on national and regional implementation.

4.2. Polish Strategic Documents on Improving the Energy Performance of Buildings (Since 2005)

In Poland, the framework for actions at the intersection of energy efficiency and heritage protection has been shaped by both EU obligations and domestic conservation priorities. Early post-2005 policy documents addressed these areas separately: energy policies focused on supply security and emission reduction, while heritage policies emphasised the preservation of material substance without considering energy performance.

As a result, there was a lack of coherence between these policy domains. For instance, the Polish Energy Policy to 2030 (2009) contained no specific provisions regarding historic buildings, and the National Heritage Protection Programme (in its successive editions) initially omitted the issue of thermal modernisation.

A shift occurred in the second half of the 2010s, driven by several factors:

• EU legislation mandating the development of long-term renovation plans;
• Growing public debate on air pollution and the energy performance of older, often historic buildings;
• The Ministry of Culture’s recognition of the need to establish guidelines reconciling conservation requirements with climate goals.

As a result, new strategies and conservation guidelines (2020) emerged—addressing, among others, energy retrofits of heritage buildings and the installation of renewable energy systems—which now serve as a bridge between conservation goals and national energy policy [11,19].

4.3. Polish Strategic Documents (Post-2005) on Building Energy Efficiency and Heritage Protection

To illustrate the evolution of national strategies concerning the energy modernisation of buildings in the context of cultural heritage protection, a comparative overview of the most relevant Polish strategic documents and implementation programmes issued after 2005 has been prepared.

Table 3. Overview of Polish strategic documents (post-2005) concerning the energy efficiency of buildings and the protection of cultural heritage, along with related implementation programmes. Author: Izabela Kozłowska.

Document (Year)	Issuing Body	Main Provisions Regarding Cultural Heritage and/or Energy Efficiency	Links to Other Documents and Implementation Programmes
Polish Energy Policy to 2030 (2009) [19]	Ministry of Economy (Council of Ministers Resolution)	Comprehensive national energy strategy to 2030—no direct reference to heritage. Focused on energy security, development of renewables, and general energy efficiency improvements. Issues related to historic buildings were not addressed.	Linked to the EU “3 × 20” targets for 2020; served as the basis for the National Energy Efficiency Action Plans (2011, 2014). Implemented through programmes such as Thermomodernisation Fund (BGK) for residential buildings—without specific provisions for heritage assets. Renovation of monuments was financed separately (via MKiDN and EU 2007–2013 funds) without integrating energy goals.
National Energy Efficiency Action Plan (e.g., 2014, 2017) [21]	Ministry of Economy/Energy	Detailed implementation plans for achieving national energy-saving targets. Recognised the specificity of heritage buildings, noting that technical and cultural constraints may prevent the application of standard retrofitting measures. The 2014 Plan states: Heritage-listed buildings form a separate group… not all interventions or technical solutions can be applied. Required by the EED Directive; consistent with the national energy policy. Later versions introduced references to heritage renovation (mainly diagnostic).	Implemented through NFOŚiGW programmes for the public sector (e.g., subsidies for energy audits). Some municipalities established special revitalisation zones combining heritage renovation with energy upgrades (funded via Regional Operational Programmes).
Polish Energy Policy to 2040 (PEP2040, 2021) [11]	Ministry of Climate and Environment (Council of Ministers Resolution)	Long-term strategy to 2040 aligned with EU climate goals (CO2 reduction, RES development). Mentions the need for energy retrofits of buildings with respect for heritage values, though vaguely. Focuses on replacing coal boilers and thermomodernising residential stock, without a dedicated heritage section.	Connected to the European Green Deal and National Energy and Climate Plan (KPEiK). Channelled national and EU funds (Cohesion Policy 2021–2027) to programmes such as Clean Air, Stop Smog, and Thermomodernisation Bonus. No separate heritage programme, though PEP2040 informed Poland’s Recovery Plan, including renovation of historic public buildings.
National Energy and Climate Plan 2021–2030 (KPEiK, 2019) [10]	Ministry of Energy/Committee for European Affairs	Implemented EU 2030 goals (emissions, RES, efficiency). Addressed heritage mainly through the lens of post-industrial transformation, calling for protection and adaptive reuse of mining heritage. Recognised legal and technical barriers in heritage energy retrofits.	Required under EU Regulation 2018/1999 (Energy Union Governance). Complementary to PEP2040. Implemented through sectoral policies (construction and climate). Synergistic with the National Urban Policy and revitalisation programmes, referencing air-quality improvement in historic city centres.
Long-Term Building Renovation Strategy (DSRB, draft 2020; final 2022) [20]	Ministry of Development and Technology	Developed under EPBD/EED requirements; outlines deep renovation of the national building stock to 2050. The 2020 draft proposed deep retrofits even for heritage buildings, criticised for excluding conservators. The final 2022 version, after consultation, added annexes on historic building renovation aligned with conservation guidelines. Promotes energy upgrades that respect authenticity (e.g., window sealing, HVAC modernisation).	Required by EPBD/EED, linked to PEP2040 and KPEiK. Consulted with MKiDN, incorporating the General Heritage Conservator’s Guidelines as an annex—an example of cross-ministerial cooperation. Implemented through an Action Plan to 2030 (EU and national funds, including NFOŚiGW programmes and tax incentives).
National Programme for the Protection of Monuments and the Care of Monuments 2019–2022 (adopted 2018) [22]	Ministry of Culture and National Heritage (MKiDN)	National conservation programme defining state priorities. For the first time, addressed energy and climate issues—including guidelines for installing PV systems and thermally upgrading historic buildings. Emphasised balancing heritage protection with user comfort and sustainability.	Based on Art. 87 of the Heritage Protection Act (updated every 4 years). Linked to the European Year of Cultural Heritage 2018. Implemented via National Heritage Board (NID) projects (e.g., development of technical standards for PV and thermal retrofits, training for conservators). Partly funded by EU Cultural and Infrastructure & Environment Programmes.
Guidelines of the General Heritage Conservator: Thermomodernisation of Historic Buildings (2020) [23]	General Heritage Conservator/MKiDN	Technical guidelines defining permissible methods of improving energy performance in heritage buildings. Recommend interior insulation (if exterior not possible), use of traditional/reversible materials, window restoration, and improved ventilation. Require energy audits approved by conservators to demonstrate achievable savings without damage.	Linked to the National Heritage Programme 2019–2022 (fulfilling one of its goals). Complementary to GKZ guidelines on moisture and ventilation. Circulated to regional conservators and applied in project evaluations and permit procedures.
Guidelines of the General Heritage Conservator: Photovoltaic Installations in Historic Buildings (2020) [24]	General Heritage Conservator/MKiDN	Detailed rules for PV installation on or near heritage buildings. Prioritise preserving visual integrity—recommend locating panels on less visible roof slopes or on the ground, prohibiting installation on valuable historic coverings (e.g., shingles, ceramic tiles). Require a visual impact assessment before approval.	Issued alongside the 2020 Thermomodernisation Guidelines as part of the GKZ climate-heritage adaptation package. Distributed to conservators with evaluation templates. Aligned with NFOŚiGW funding schemes, which require heritage-compliant opinions for PV projects.

organises these documents according to their relevance to two key public policy domains—energy efficiency and heritage conservation—and indicates how specific strategies have influenced conservation practice and the implementation of EU objectives (e.g., EPBD, EED, the Renovation Wave, and the European Green Deal).

The comparison combines analytical and interpretive perspectives: alongside the substantive content of each document, it highlights their practical implications (e.g., implementation via NFOŚiGW, MKiDN, RPO (Regionalne Programy Operacyjne), and KPO (Krajowy Plan Odbudowy) programmes) and summarises academic and professional evaluations of their effectiveness.

This overview captures the turning point when Polish policy began to genuinely integrate climate and heritage goals—a process that commenced only after 2018, following the development of the Long-Term Building Renovation Strategy (Długoterminowa Strategia Renowacji Budynków (DSRB)) and the General Heritage Conservator’s Guidelines (Wytyczne Generalnego Konserwatora Zabytków) [23,24].

The data presented in Table 3 provide a foundation for further analysis of discrepancies in the pace and scope of EU policy implementation in the Polish context and for identifying areas requiring legal, financial, or methodological improvement.

4.4. Summary of Results

The results of the strategic document analysis have been synthesised into two comparative tables (

Table 4. Overview of key European Union documents (post-2005) concerning the energy efficiency of buildings and the protection of cultural heritage, and their impact on conservation practice. Author: Agnieszka Rek-Lipczyńska.

Document (Year)	Impact on Heritage Conservation Practice and Evaluation
Directive 2010/31/EU on the Energy Performance of Buildings (EPBD, recast 2010) [6]	Initially, the exemption of heritage buildings helped protect their historic fabric from inappropriate retrofitting, but it also slowed efforts to improve their energy performance. Many listed buildings in both the EU and Poland remained outside energy-efficiency standards. Critics argue that excluding this category entirely represented a missed opportunity to reduce energy consumption, calling instead for a more balanced approach rather than blanket exemptions.
Directive 2012/27/EU on Energy Efficiency (EED, 2012) [50]	Encouraged Member States to establish support mechanisms for renovation; however, in practice, the renovation of heritage buildings progressed more slowly. Public institutions often relied on exemption clauses, postponing upgrades to historic structures. Scholarly analyses emphasise the need to balance efficiency requirements with the protection of artistic and cultural values, noting the insufficient pace of improvement in the energy performance of historic buildings compared with other sectors.
Directive 2018/844/EU amending the EPBD and EED (2018) [51]	Broadened the scope of building modernisation and stimulated discussion on the appropriate ways to renovate heritage properties. In Poland and other Member States, this prompted heritage authorities to participate in drafting long-term renovation strategies. However, experts noted that Poland’s initial draft of the strategy ignored conservation guidelines and focused mainly on deep retrofits, which provoked criticism.
European Green Deal (2019) [8]	Provided a strong political impetus for the energy renovation of buildings, including heritage assets, by mobilising funding and research initiatives. Nevertheless, the absence of explicit heritage references in the core document drew criticism from NGOs. Europa Nostra’s European Cultural Heritage Green Paper [62] highlighted how cultural heritage could actively support Green Deal objectives. It advocated for renovations that enhance energy efficiency while protecting cultural values—an approach increasingly reflected in subsequent EU initiatives.
Renovation Wave—European Commission Communication (COM, 2020) [5]	Directed governmental attention to the need for modernisation in the heritage sector. However, experts warned of potential risks: the European Commission Expert Group on Cultural Heritage and Climate Change (2020) cautioned that uncontrolled implementation of new energy technologies in historic structures could damage their authenticity more severely than climate impacts themselves. This led to the development of specialised guidance (e.g., EN 16883 standard [63]) and targeted funding mechanisms for heritage renovation (e.g., NFOŚiGW/FEnIKS programmes in Poland). Overall, the initiative was assessed positively as a catalyst for debate on “green” heritage revitalisation.
EU Strategy on Adaptation to Climate Change—European Commission Communication (2021) [4]	Linked to the European Green Deal and the Paris Agreement, complementing emission-reduction policies with an adaptation component. Implementation occurs via national adaptation plans and financial mechanisms (e.g., Climate Fund). From a cultural perspective, it refers to UNESCO and Council of Europe frameworks (e.g., Strategy 21 on Cultural Heritage) but lacks concrete instruments. Evaluation: Scholars and heritage experts criticised the omission of cultural aspects in adaptation planning, noting that the absence of heritage-specific guidelines weakens resilience to climate threats (e.g., extreme weather). In response, the EU Member States’ OMC Working Group produced the 2022 report Strengthening Cultural Heritage Resilience for Climate Change, recommending the inclusion of heritage in adaptation strategies and the development of risk assessment methodologies [64].
New European Bauhaus (initiative, 2020–2021) [18]	Increased awareness that cultural heritage can serve as a valuable resource in the green transition, inspiring numerous revitalisation projects of historic spaces aligned with sustainable development principles. In Poland, adaptive reuse of post-industrial buildings and the renewal of historic housing estates received support as “NEB beacons.” Critics, however, emphasised that the initiative remains “soft”—it lacks regulatory force—so its success depends largely on adoption by national and local authorities.

and

Table 5. Overview of key Polish strategic documents (post-2005) concerning the energy efficiency of buildings and heritage protection, and their impact on conservation practice. Author: Izabela Kozłowska.

Document (Year)	Impact on Heritage Conservation Practice and Evaluation
Polish Energy Policy to 2030 (2009) [19]	Impact: The policy set the direction for national energy legislation and programmes (e.g., the Energy Efficiency Act of 2011) but remained neutral regarding heritage protection. The omission of historic buildings was later criticised as a policy gap—between 2010 and 2015, heritage structures were not prioritised for energy upgrades, which perpetuated their poor energy performance.
National Energy Efficiency Action Plans (2014, 2017) [22]	Impact: These implementation plans formally acknowledged the specific character of heritage buildings, noting that cultural and technical constraints may prevent the use of standard modernisation methods. For example, the 2014 Plan states that: heritage-listed buildings form a distinct group… not all interventions or technical solutions can be applied. While aligned with the EED Directive and national energy policy, their practical influence was limited by the absence of dedicated funding tools. Some municipalities established revitalisation zones linking heritage renovation with energy efficiency (funded through Regional Operational Programmes). Scholars highlight that more detailed guidelines were needed—a gap addressed only after 2018.
Polish Energy Policy to 2040 (PEP2040, 2021) [11]	Evaluation: Both governmental and independent analyses pointed out that PEP2040 did not give sufficient attention to historic buildings. In practice, the responsibility for detailed regulation was transferred to the Long-Term Renovation Strategy and the Ministry of Culture. Experts noted that the lack of proactive, heritage-focused measures may hinder energy-efficiency goals, as this building group constitutes a significant portion of urban housing stock in historic city centres.
National Energy and Climate Plan 2021–2030 (KPEiK, 2019) [10]	Impact: Introduced the issue of post-industrial heritage as part of the energy transition, resulting in inventories and protection efforts for historic industrial sites (e.g., mines). Concerning building efficiency, it mainly described the challenges without proposing concrete solutions. Nonetheless, it served as a starting point for the development of the renovation strategy and raised awareness of heritage-related issues among other ministries.
Long-Term Building Renovation Strategy (DSRB, draft 2020; final 2022) [20]	Impact and Evaluation: The DSRB is the first Polish document to systemically address the thermal modernisation of heritage buildings. Its final version was positively evaluated by the conservation community for integrating their recommendations. However, the strategy’s ambitious goals for deep renovation were seen as difficult to achieve without additional funding and expertise. Pałubska and Zalasińska noted that the strategy enforces a new standard of collaboration between conservators and energy specialists—an improvement that still requires innovation to ensure authenticity-preserving modernisation [56].
National Programme for the Protection of Monuments and the Care of Monuments 2019–2022 (adopted 2018) [22]	Impact: Marked a turning point by officially incorporating climate and energy themes into heritage policy. It produced key conservation guidelines (discussed below) that are now used by regional heritage authorities. Academic assessments are positive, noting that Poland was among the first countries in the region to develop comprehensive standards for “green” investments in heritage. The challenge remains continuity—future editions should broaden the scope of these initiatives.
Guidelines of the General Heritage Conservator: Thermomodernisation of Historic Buildings (2020) [23]	Practical Impact: Standardised conservation practice nationwide—previously, decisions were highly discretionary. Public investors (e.g., municipalities, parishes) now rely on these guidelines to prepare energy retrofit projects for heritage assets. Scholars regard them as a step forward, though their non-binding nature limits their enforcement. Further extensions are recommended, such as guidance on improving heating-system efficiency in addition to insulation.
Guidelines of the General Heritage Conservator: Photovoltaic Installations in Historic Buildings (2020) [24]	Impact: Significantly streamlined administrative practice—previously, decisions on PV systems in heritage sites varied by region. The guidelines now provide clarity for investors and a framework for conservators to reject harmful designs while approving well-integrated ones. In 2020, applications for PV systems on heritage buildings rose sharply (812 applications, over half approved), suggesting that the guidelines facilitated the legal implementation of properly designed projects. The literature recommends continued monitoring of these installations and periodic updates to reflect technological advances.

), which form a key component of the empirical section of this study. These compilations illustrate the evolution of European Union and Polish policies and legal frameworks regarding the energy efficiency of buildings, with particular emphasis on their impact on heritage conservation practice.

The desk research methodology enabled the identification of policy shifts, systemic gaps, and areas of conflict between the goals of heritage protection and the priorities of climate and energy policy.

Within this framework, Table 4 and Table 5 serve as analytical tools for a comparative examination of EU and national strategic documents. Their structured analysis made it possible to trace changes in the approach to energy retrofitting of heritage buildings and to assess the degree of implementation of European climate objectives within Poland’s heritage protection policies.

Table 4 presents the key legal acts and policy initiatives of the European Union (2005–2025) that have shaped the legislative framework for improving the energy performance of historic buildings.

Table 5, in turn, summarises the corresponding national documents, ranging from the Polish Energy Policy to 2030 to the Guidelines of the General Heritage Conservator (2020), thereby allowing for an analysis of how EU objectives have been translated and adapted into the Polish policy context.

4.4.1. Implementing Bodies

NFOŚiGW, Ministry of Funds and Regional Policy, voivodeship self-governments. Although not a single document, it is worth noting implementation programmes that operationalise the above strategies: e.g., Priority VIII of the Operational Programme Infrastructure and Environment (OPI&E) 2014–2020 (Infrastructure and Environment—protection of cultural heritage with energy-efficiency components), the EEA and Norway Grants (projects to improve the energy performance of museums and ecclesiastical buildings), and more recently the NFOŚiGW programme “Improving Energy Efficiency in Historic Public Buildings” (2022–2025) with a budget of PLN 0.5 billion. The NFOŚiGW programme supports comprehensive thermal retrofits of 45 historic public buildings (offices, schools, museums), including RES installations. Many regions have also launched their own calls (RPO) combining the revitalisation of historic city centres with improvements to building energy performance.

4.4.2. Linkages

Funding for these programmes largely derives from the EU (ERDF under Cohesion Policy, the Recovery and Resilience Facility–KPO, the Modernisation Fund). Their launch followed growing awareness and strategic commitments (e.g., NFOŚiGW explicitly references PEP2040 and DSRB). Implementation consists of co-financing investments compliant with conservation guidelines—applications require a positive opinion from the Regional Heritage Conservator (Wojewódzki Urząd Ochrony Zabytków (WKZ)) regarding the scope of works.

4.4.3. Impact

These programmes are practical tools for delivering policy goals. In 2014–2020, they enabled dozens of heritage modernisations carried out with respect for cultural values (e.g., thermal upgrades of historic universities, hospitals). Assessments point to improved user comfort and lower operating costs without visible harm to heritage character, confirming the effectiveness of the standards developed. Critical remarks concern scale—needs far exceed available resources, and many smaller heritage assets (e.g., tenement houses) are not eligible under current schemes. This suggests the need to expand financial support in the coming years.

4.5. Comparative Analysis of EU and Polish Policies

4.5.1. Scope and Approach

EU policies are framework-oriented and incentivising—they set goals and mechanisms (regulations, funds) binding on all Member States while leaving them some latitude in implementation. Regarding historic buildings, the EU initially limited itself to exemptions and general recommendations, while responsibility for detailed solutions was devolved to the national level. Poland initially used this flexibility, treating monuments leniently within efficiency regulations, but addressed their proactive modernisation with a delay. Only increasing pressure (both EU—e.g., the long-term renovation strategy requirement—and domestic—air pollution, rising energy costs) led to integration of the two domains: Polish institutions began to cooperate more closely (example: DSRB consultations with the participation of conservators). Compared to the EU, Polish documents developed more operationally detailed guidance, reflecting the need to apply general goals to specific local conditions. The European Union has indicated the general concept (e.g., the refurbishment of buildings), while the Polish government has been tasked with elaborating the specific methodology for undertaking such projects in heritage structures.

4.5.2. Hierarchical Linkages

Most Polish energy strategies directly responded to EU policies (e.g., KPEiK was prepared pursuant to Regulation (EU) 2018/1999, and DSRB was mandated by the EPBD). At the same time, Polish cultural authorities initiated anticipatory national actions not directly required by EU law—e.g., the 2020 GKZ Guidelines or the 2019–2022 National Heritage Programme—which nonetheless aligned with broader international trends (consistent with Council of Europe and ICOMOS recommendations). EU and Polish documents thus stand in a relationship of subsidiarity: EU directives created the legal framework and impetus for action, while Polish regulations and guidelines adapted these requirements to local conditions (e.g., the specificity of Poland’s heritage stock, the technical condition of tenements, and the fiscal capacity of municipalities).

4.5.3. Differences in Priorities

At EU level, energy efficiency was the goal, while heritage protection was considered a value that could not be violated—hence the precautionary approach involving exemptions and the principle of ‘do no harm’ to monuments. In Poland, especially from the perspective of conservation services, the situation was different: monuments were protected first and foremost, and increasing their efficiency was initially seen as an optional additional benefit. Only in recent years have these priorities become more balanced. Polish documents increasingly treat efficiency improvements in monuments as part of their stewardship, while the EU (Renovation Wave, adaptation policy) is articulating more strongly that the climate transition must consider cultural context. For example, Europe has created knowledge-exchange platforms (OMC, New European Bauhaus), in which Polish experts participate and help to shape the direction of action.

4.5.4. Implementation Instruments

The EU provides substantial funding that determines Member States’ capacity for renovation. Poland has taken advantage of this—since 2007–2013, successive Operational Programmes have financed heritage renewal (initially mainly for tourism, without an energy focus). In 2014–2020 and especially 2021–2027, funds were reoriented: purely conservation projects gave way to projects enhancing the functionality and energy performance of historic buildings. For instance, the FEnIKS 2021–2027 programme (Fundusze Europejskie na Infrastrukturę, Klimat, Środowisko 2021–2027/European Funds for Infrastructure, Climate and Environment 2021–2027), (successor to Operational Programme “Infrastructure and Environment” 2014–2020 (OPI&E)) integrates climate objectives with heritage protection, exemplified by the 2022 NFOŚiGW call for thermomodernisation of monuments [45]. As a result, strategies translate into tangible actions. National instruments also play a role: tax incentives (e.g., the 2019 “Pałacyk+” heritage relief, which can be combined with energy retrofits) and the Revitalisation Act (2015) equip municipalities with tools for the comprehensive renewal of historic districts, including efficiency upgrades [65].

4.5.5. Impact on Practice and Critical Observations

Both EU and Polish frameworks have shifted conservation practice from a conservative stance towards a more pragmatic, multidisciplinary model. In Poland, regional conservators increasingly participate in planning energy modernisations at the concept stage (as advocated in renovation strategies). Projects have become multidisciplinary: architects, engineers, and conservators collaborate to meet technical and aesthetic requirements simultaneously—previously a weak point. Despite these positives, the literature points to several issues:

• Insufficient dissemination of knowledge—many owners are unaware of new opportunities or fear bureaucracy;
• Economic barriers—even with grants, heritage modernisation is costlier, and not all owners qualify;
• Regulatory gaps—GKZ guidelines lack the status of a regulation, and the Heritage Protection Act still does not reference climate protection or energy efficiency. Researchers also underline the need for monitoring and evaluation of outcomes (whether heritage values have been preserved and energy savings achieved).

In sum, comparatively, the EU has set goals and created legal and financial conditions for the “green” modernisation of monuments, while Poland—despite initial delays—has developed concrete tools and standards that may serve as a model for other countries. In both cases, there has been a clear evolution from treating energy efficiency and heritage protection separately to perceiving them as complementary goals within sustainable development.

4.6. Empirical Research on the Energy Modernisation of Heritage Buildings in Poland (2015–2025)

To develop a national spatial characterisation of the heritage stock, we used open data from the National Heritage Board of Poland (Narodowy Instytut Dziedzictwa (NID)), available via otwartedane.nid.pl. [26]. This database includes the complete register of immovable monuments in Poland, with information on location, typology, use, period of construction, and form of protection. The data were downloaded in formats suitable for further spatial and statistical processing (CSV, SHP).

The NID resources enabled the extraction of information on:

• The number of heritage assets by administrative division (voivodeships and counties;
• Typology (sacral, residential, public utility, post-industrial, defensive, etc.);
• Spatial distribution of buildings nationwide (geographical coordinates).

The compiled dataset supports quantitative and cartographic analyses of Poland’s heritage stock, accounting for regional and functional differences.

Within this article, NID data serve as a reference baseline for:

• Delineating a map of heritage concentration—by calculating the number of assets per unit area (e.g., per 100 km²) in each voivodeship;
• A spatial comparison with data on modernisation projects is enabled, thereby allowing for the juxtaposition of the number of monuments with the number of energy retrofit investments (e.g., Clean Air, ROP, or MKiDN programmes);
• Identifying potential conservation–energy conflict areas—by analysing the overlap of high heritage concentration with regions of intense modernisation activity.

Using NID data made it possible to determine the scale and spatial distribution of the heritage stock, providing a benchmark for assessing the degree of integration between conservation and energy policies. The information enabled the construction of spatial indicators, such as:

• Heritage density index—number of monuments per 100 km² (Figure 2);
• Modernisation-to-heritage ratio—number of modernisation projects per 100 monuments (Figure 3);
• Conservation risk coefficient—the relationship between the intensity of modernisation and the formal supervision of the Regional Heritage Conservator (WKZ) (Figure 3).

This dataset constitutes a key empirical component of the study, allowing an objective assessment of the scale of modernisation activities in the context of cultural heritage protection in Poland.

The analysis of indicators W1–W12 (

Table 6. Empirical indicators of energy modernisation of heritage buildings in Poland (2015–2025). Author: Izabela Kozłowska, Agnieszka Rek-Lipczyńska.

Code	Indicator Name	Calculation/Source	Result (2025)	Interpretation/Conclusions
W1	Number of immovable monuments	Based on NID database (2024): approx. 78,550 objects	78,550	The number of protected buildings in Poland has remained stable since 2015, with a slight increase (~2%) due to registry updates.
W2	Number of conservation interventions	Estimate based on WKZ public reports and MKiDN annual statements—approx. 4800 per year, 40% involving construction works	~48,000 (2015–2025)	The growing number of conservation interventions indicates increased renovation activity, though only part relates to energy measures.
W3	Number of publicly funded projects	mapadotacji.gov.pl—2320 projects (2015–2025), about 18% involving heritage assets	420 projects	Around 420 projects targeting heritage sites were identified within POIiŚ, ROP, KPO and NFOŚiGW programmes.
W4	Share of energy projects among all conservation interventions	(420/48,000) × 100	0.9%	The very low share of energy-related projects among conservation works highlights the limited implementation of climate-oriented modernisations.
W5	Average funding per energy project	Based on NFOŚiGW and ROP data: PLN 1.42 billion/420 projects	PLN 3.38 million	Energy projects in heritage buildings are relatively expensive due to technological and conservation requirements.
W6	Share of regions with high intensity of thermal retrofits	(Number of Clean Air applications/number of monuments per voivodeship) × 1000	avg. 13.6; max: Mazowieckie 21.4; min: Opolskie 7.9	Regions with many heritage buildings also show high modernisation activity, increasing the risk of conservation conflicts.
W7	Ratio of applications to conservation permits	(1,067,838/48,000) ≈ 22:1	22.2	Only a small fraction of potentially relevant investments undergoes formal WKZ supervision.
W8	Dynamics of heritage funding by MKiDN	Total grants increased: PLN 94 million (2015)→PLN 183 million (2024)	+95%	Although conservation funding nearly doubled, it did not translate into a proportional rise in energy retrofits.
W9	Number of energy performance certificates for pre-1945 buildings	GUNB 2025 data: 62,000 certificates (~8% of total registry)	62,000	Low representation of historic buildings in the energy certificate registry confirms the limited uptake of energy audits.
W10	Share of projects using innovative technologies (e.g., thermal coatings)	Qualitative review 2020–2025: ~25 EU pilot projects, 3 in Poland	0.1%	Innovative technologies are used very rarely despite their high potential [63,64,65,66,67,68].
W11	Modernisation penetration rate	(420 energy projects/78,550 monuments) × 100	≈0.5%	Only half a percent of heritage buildings underwent energy modernisation—an indication of a major retrofit gap.
W12	Regional conservation–energy conflict coefficient	(Projects without WKZ approval/all energy projects) × 100	≈40%	An estimated four in ten projects may have proceeded without full conservation oversight—posing a serious risk to authenticity.

) reveals a significant disparity between the scale of modernisation efforts financed through energy programmes and the actual scope of conservation oversight.

Despite over one million applications submitted under the Clean Air programme (W7), less than 1% relate to buildings with verified heritage value (W4, W11). Only about 0.5% of the total heritage stock has been covered by interventions aimed at improving energy efficiency. The conservation–energy conflict coefficient (W12 ≈ 40%) suggests that a substantial share of works may have been carried out without adequate supervision by conservation authorities (WKZ), increasing the risk of loss of authenticity and material integrity.

Based on a review of public project databases (mapadotacji.gov.pl [43], MKiDN grant reports, NFOŚiGW calls [45]), it is estimated that no more than approximately 0.5% of Poland’s heritage stock (≈78–79 thousand buildings) underwent energy-related modernisation between 2015 and 2025 (W11). This figure represents an author’s estimation that requires further project-by-project verification and should be understood as an order-of-magnitude approximation rather than a definitive result.

Financial data indicate that energy retrofitting projects in heritage buildings are among the most expensive types of renovation investments (averaging PLN 3.38 million, W5), yet they constitute only a marginal fraction of all conservation works. On the other hand, the increasing funding allocations from MKiDN (W8) and the growing network of energy-efficiency and renewable-energy programmes (NFOŚiGW [45], ROP) create a potential for stronger integration between conservation and climate objectives—provided that dedicated procedures and evaluation standards are developed to assess the impact of modernisation on the heritage value of protected buildings.

The heritage building stock remains almost entirely outside the effective reach of Poland’s energy transition. There is no system for monitoring thermal modernisation works in historic structures, and available public data reveal both the scale of neglect and the potential areas of conflict between climate policy and heritage conservation.

The diagram “Indicators of energy modernisation and conservation supervision in Polish heritage buildings (2015–2025)” (Figure 3) clearly illustrates the disproportion between the scale of national energy efficiency programmes and the marginal inclusion of heritage buildings within them. Only 0.9% of all conservation interventions involved energy-related actions, while approximately 40% of energy projects were implemented without formal supervision by heritage authorities.

The analysis of empirical indicators (W4, W7, W11, W12) highlights a profound imbalance between the scope of Poland’s energy modernisation policies and their actual implementation in the heritage sector. As shown in Figure 3, merely 0.9% of conservation interventions between 2015 and 2025 included measures improving energy performance (W4), confirming that energy efficiency remains a peripheral element of heritage protection policy. On average, 22 modernisation applications (e.g., under the Clean Air programme) were submitted for every single conservation decision issued by the voivodeship heritage offices (W7). This reveals a systemic mismatch between environmental policy instruments and conservation procedures. Only 0.53% of the entire stock of listed monuments underwent any form of thermal modernisation (W11), demonstrating the negligible penetration of energy transition processes within the heritage sector. Furthermore, an estimated 40% of energy projects were executed without WKZ approval (W12), which raises serious concerns about the loss of authenticity, material integrity, and architectural coherence in historic buildings.

Collectively, these findings confirm that Polish heritage assets remain largely excluded from the ongoing energy transition. The absence of an integrated monitoring system allows for fragmented and often unsupervised modernisation activities, undermining both cultural and environmental objectives.

To address this gap, it is crucial to develop an integrated policy framework linking the requirements of the Energy Performance of Buildings Directive (EPBD) [6] with the Polish Heritage Protection Act [6]. Introducing standardised assessment procedures for energy retrofits in heritage buildings, including low-impact, reversible techniques such as thin-film insulation or adaptive HVAC systems, would help align energy efficiency goals with the principles of authenticity, compatibility, and reversibility that underpin sustainable heritage conservation [66,67,68,69,70,71].

The diagram “Conceptual alignment between national heritage and energy-efficiency indicators (W4–W9) and European policy frameworks (EPBD, European Green Deal, New European Bauhaus)” illustrates the evolution of the relationship between technical and legal requirements for energy performance (EPBD), climate and investment objectives (European Green Deal, Renovation Wave), and the cultural and social dimensions of design (New European Bauhaus) (Figure 4).

National indicators demonstrate that the implementation of EPBD and Green Deal principles in the heritage sector remains limited (W4–W7, W11–W12), while new initiatives such as the New European Bauhaus (NEB) are beginning to generate qualitative improvements in design practice (W8–W9).

Overall, the results confirm that Poland is currently in a hybrid phase of transformation, in which energy and conservation policies are only starting to integrate—in line with the emerging concept of “heritage-inclusive renovation strategies.”

Like most EU Member States, Poland is in the process of developing institutional frameworks that will enable the practical implementation of this model. The low indicator values (W4–W12) confirm the need for systemic legislative, financial, and educational reforms to strengthen the integration of heritage protection within climate and energy agendas.

The term “heritage-inclusive renovation strategies” refers to the integration of climate and energy objectives with the protection of the historical, architectural, and cultural values of buildings.

The concept began to appear in EU expert reports and policy documents after 2018, following the recast of the Energy Performance of Buildings Directive (Directive 2018/844/EU) [51] and the launch of the Renovation Wave (2020) [5] and New European Bauhaus (2021) [18] initiatives.

In practice, heritage-inclusive renovation strategies imply that:

• Modernisation measures must respect the character, materiality, and authenticity of heritage buildings;
• National and regional renovation plans are required to include historic buildings within long-term strategies, in line with EPBD Recitals 12 and 13;
• EU funding instruments (e.g., FEnIKS, LIFE, Horizon Europe) should prioritise projects that combine energy efficiency with heritage conservation, supporting design approaches that are sustainable, reversible, and culturally sensitive.

This evolving framework marks a shift from viewing heritage as an obstacle to climate action toward recognising it as a strategic resource in Europe’s green transformation, bridging technological innovation with cultural continuity.

5. Discussion

This final section synthesises the key findings of the research, outlines practical recommendations for policymakers and conservation practitioners, and identifies areas for further research. It also reflects on the potential for replicating heritage-sensitive retrofit strategies across diverse European contexts.

5.1. Definitional and Practical Collisions

In the context of the energy transition, there is a clear discrepancy between the broad conceptual definitions adopted in EU strategic documents and the precise legal definitions established at the national level. At the European level, a broad understanding of architectural heritage is applied—for instance, the Granada Convention (1985) calls for the protection of “any architectural heritage,” adapted to the requirements of modernity and sustainable development [72]. Such EU-level frameworks typically employ general terms such as “historic buildings” or “cultural heritage” without specifying detailed criteria.

In contrast, national law usually defines “monuments” much more precisely. In Poland, for example, a zabytek (monument) is legally defined as an immovable or movable object created by human activity, constituting evidence of a past era or event, whose preservation is in the public interest due to its historical, artistic, or scientific value [3]. This means that only officially recognised objects meeting specific evaluative criteria and formally listed in heritage registers or inventories are protected by law.

The absence of coherent and harmonised criteria distinguishing between “historic buildings,” “traditional architecture,” and “legally protected monuments” leads to major interpretative and regulatory conflicts. Each Member State defines and classifies heritage assets in its own way, which generates definitional inconsistencies in the implementation of EU programmes. For instance, EU energy directives such as the EPBD allow Member States to exempt protected historic buildings from mandatory energy efficiency requirements [6]. However, these exemptions typically apply only to formally listed properties, neglecting many historic buildings that lack official monument status.

Experts therefore call for broader and more inclusive criteria, recommending that renovation guidelines cover not only listed monuments but also all buildings “worthy of preservation” for their historical or cultural value [17]. In practice, however, there is no unified standard: traditional architecture—such as rural vernacular houses or early 20th-century urban tenements—often falls outside the narrow legal definition of a monument and thus escapes protection. As a result of these definitional discrepancies, a significant protection gap has emerged for many valuable buildings undergoing energy retrofitting. Numerous structures of genuine heritage value—such as old residential houses, traditional rural buildings, or small-town architecture from the early 20th century—are not formally recognised as monuments and thus remain outside the scope of conservation supervision.

Statistical data illustrate the scale of the problem: in Poland, buildings erected before 1945 constitute roughly 20% of the total building stock, yet only 2–3% of all buildings are formally listed as protected monuments. This means that the vast majority of historic building fabric lacks legal protection, even though it meets basic age or typological criteria. Consequently, when large-scale energy renovation programmes are launched under climate policy frameworks, many such structures undergo modernisation without the involvement of heritage authorities, as there is no legal basis for their oversight. European funds and national grants for improving building energy performance also do not consistently differentiate between heritage and non-heritage buildings, leaving such distinctions to national definitions. As a result, when a country does not recognise a given category of historic architecture as a “monument,” modernisation proceeds without special requirements for maintaining its historic character.

The practical consequences of this definitional gap are alarming: uncontrolled loss of authenticity, architectural detailing, and material integrity in many renovated buildings. In the absence of conservation oversight, thermal retrofitting works often interfere with original fabric—for instance, removing or covering original façades with modern insulation systems, as in the case of the house in Malechowo (Figure 5).

Original windows, doors, stucco, or brick façades are often replaced or concealed; applying layers of polystyrene or mineral wool to historic masonry has become a common practice, dramatically altering building appearance. Once removed, these features can only be reconstructed as modern replicas, devoid of their original authenticity. Moreover, such interventions frequently disrupt the moisture balance of traditional wall structures, leading to accelerated material decay.

As a result of inadequately planned energy retrofits, the distinctive features of many historic buildings are being irreversibly lost—their authentic aesthetic and historical value erased in pursuit of thermal performance. The priority of energy efficiency is thus too often achieved at the expense of heritage conservation, producing “modernised” buildings with smoothed façades, plastic windows, and synthetic finishes that only superficially resemble their historic originals [56,57].

5.2. The Regulatory Gap and Divergent National Approaches

A critical reflection reveals a persistent lack of coherence between EU legislation—notably the Energy Performance of Buildings Directive (EPBD) and the Energy Efficiency Directive (EED)—and their national-level implementation across Member States. While the EU legal framework allows for certain exemptions for protected historic buildings, the way these provisions are interpreted and applied varies considerably between countries.

The exclusion of heritage buildings from energy performance regulations serves a dual purpose: on the one hand, it protects the historical fabric from potentially harmful interventions that could compromise its authenticity; on the other, it reinforces the low energy efficiency of the historic building stock by leaving it outside the mainstream of energy transition policies.

This legal paradox—where protection equates to exemption—creates a structural barrier to innovation. Without harmonised mechanisms that reconcile conservation objectives with climate goals, most heritage buildings remain in a regulatory limbo: protected from alteration but excluded from modernisation. As a result, the sector faces a “double deficit”—a lack of energy efficiency and a lack of adaptive capacity to climate change. Furthermore, the diversity of national approaches deepens this inconsistency. Some Member States, such as Italy [73], Denmark [74], or the Netherlands [75], have developed specialised guidelines and financial schemes for energy renovation of listed buildings, while others, including Poland, are still in the process of defining integrated frameworks. The absence of EU-wide operational standards—for example, for assessing the impact of thermal upgrades on heritage materials—hampers comparability and coordinated progress. This regulatory gap underscores the need for EU-level recommendations on heritage-compatible energy renovation, supporting both conservation integrity and climate adaptation.

5.3. Innovative Solutions in the Energy Modernisation of Historic Buildings

The ongoing energy transition demands innovative approaches that reconcile the principles of sustainable development with the preservation of cultural heritage. Traditional thermal retrofitting techniques—such as the application of thick external insulation layers—often prove inappropriate or harmful for historic structures. Their use can lead to the loss of original material, the erasure of architectural detail, and the diminution of façade authenticity.

Consequently, recent research and practice have increasingly focused on minimally invasive and reversible technologies that improve energy performance without altering the building’s structural or aesthetic character [66,67,68,69,70,71]. Examples include:

• Internal insulation systems using capillary-active, vapour-permeable materials (e.g., calcium silicate, aerogel plasters), which regulate moisture while improving thermal comfort;
• Thin-layer reflective coatings and transparent thermal insulations, applied to preserve historic façades without visual impact;
• Energy-efficient window retrofits, such as replacing glazing with vacuum or low-emissivity panes while retaining original wooden frames;
• Adaptive HVAC systems and heat recovery ventilation integrated discreetly into existing structures, ensuring both comfort and material preservation;
• Renewable energy integration through reversible solutions, such as ground-source heat pumps or low-visibility photovoltaic systems (BIPV), designed to respect heritage silhouettes.

These approaches embody the principles of “reversibility, compatibility, and minimal intervention,” which are increasingly recognised as the foundation of heritage-compatible energy retrofitting. They align with the EPBD’s evolving framework (2023 revision), which encourages innovative, low-impact methods for the deep renovation of historic buildings while maintaining their cultural significance and material integrity (

Table 7. Projects illustrating innovative solutions in the field of architectural adaptation and energy modernisation of historic buildings, serving as exemplary examples of good practice. Author: Agnieszka Rek-Lipczyńska.

Facility (Location)	Protection Status	Scope of Modernisation and Technologies	Results and Effects
Villetta Serra, Genoa (Italy) [76]	The building is listed in the register of monuments (local conservator)	Thermal modernisation ‘from the inside’: insulation of walls from the inside (while preserving the original façade); insulation of the ceiling above the basement and the roof; replacement of leaky windows from the 1970s with windows with a very low U-value (0.7–0.8 W/m2K); modernisation of the HVAC system—installation of a heat pump (ground source) with vertical probes and underfloor heating/cooling; optional mechanical ventilation system with heat recovery. Photovoltaic panels (hidden behind the parapet) have been discreetly integrated into the terrace to provide additional renewable energy.	The comprehensive modernisation will reduce the building’s energy demand by approx. 70–80%, bringing it closer to the nZEB standard. Simulations indicate that the walls will achieve a U-value of approx. 0.30 W/m2K (previously ~1.3) and that the strict insulation requirements for the roof and windows will be met. All work was carried out in consultation with the conservator—no changes were made to the historic façade, and new installations were placed non-invasively, using existing recesses and windows (e.g., free spaces near the staircase). This example proves that it is possible to reconcile the preservation of authenticity with the achievement of high energy efficiency.
Primary school, Olbersdorf (Saxony, Germany) [77,78]	The building is listed in the state register of monuments (Weimar Republic architecture)	Comprehensive thermal modernisation of a school building dating from 1927/28. Innovative external insulation with a minimum thickness was used: 2 cm thick VIP vacuum panels (λ ≈ 0.008), covered with a 3 cm layer of PUR foam and thin-layer plaster—a total of only ~5–6 cm of insulation on the façade, in accordance with the conservator’s recommendation. The window frames were replaced with wooden box windows with thermal insulation packages and integrated air vents (so-called Zuluftkastenfenster) for ventilation. A hybrid classroom ventilation system with automation was introduced: gravitational air supply through box windows (air preheated in the space between the windows) + mechanical exhaust ventilation with heat recovery controlled by CO2 sensors. To reduce overheating in summer, electrochromic (electrically tinted) windows and slatted blinds in the space between the window sashes were used; automatic night ventilation (free cooling) was also provided. The modernisation was complemented by the replacement of the heat source and heating system.	Target energy standard: the so-called 3-Litre-Haus—heating and ventilation demand approx. 34 kWh/m2 per year (previously primary energy ~174 kWh/m2∙a), which means a reduction in energy consumption for heating purposes by ~80%. Actual measurements confirmed a significant improvement in efficiency and comfort: the problem of overheating and insufficient lighting in rooms was eliminated (better daylighting + new energy-efficient lighting). Although, for technical reasons, the planned wall insulation was not fully achieved (difficulties with fixing the VIP panels—they were eventually partially dismantled), the investment is a model example of the modernisation of a historic building, significantly reducing operating costs and improving learning conditions with minimal interference with the original façade.

).

In this sense, innovation becomes not merely a technological matter but an ethical and methodological challenge—seeking equilibrium between energy efficiency, aesthetic authenticity, and cultural continuity.

The existing literature provides numerous examples of innovative approaches to the revitalisation of historic buildings. The following projects showcase innovative solutions in the field of architectural adaptation and energy modernisation of historic buildings, which are examples of good practice.

• Villetta Serra is a historic 19th-century villa located in the centre of Genoa. The building is currently under the supervision of the Archaeology, Art and Landscape Superintendency, as it has been recognised as an architectural monument (registered entry). The owner, in collaboration with the Polytechnic University of Genoa, initiated an innovative project in 2016–2023 to modernise the villa, aiming to harmonise conservation measures with the achievement of a nearly zero-energy building (nZEB) standard. After consultation with the conservator, it was decided that the insulation of the external walls on the façade side must not interfere with the historical appearance of the building. Therefore, the installation of standard thick insulation on the outside (mineral wool, polystyrene) was abandoned. Instead, where technically possible, the internal walls were insulated with materials with high water vapour permeability, which prevents moisture from accumulating in the structure. Additionally, the ceiling above the basement and the flat roof were insulated.
  The old, leaky window frames (last replaced in 1978) were replaced with contemporary wooden windows that are both aesthetically pleasing and energy efficient, with a very low U-value of ~0.7 W/m²K. This upgrade enhances thermal insulation while maintaining the historic window layout. In terms of the installation systems, a contemporary HVAC system was installed in the villa. The provision of central heating and cooling is facilitated by a ground source heat pump with vertical probes, which are connected to low-temperature underfloor heating. This system has the capacity to function as a surface cooling mechanism during the summer months. Mechanical ventilation with heat recovery was also incorporated into the design, with ventilation devices being discreetly integrated into the existing structure. This was achieved by utilising existing recesses in the walls, created during previous renovations, and the shafts of the newly installed lift, thereby avoiding the need for chiselling new channels in the historic walls. This is complemented by an intelligent building energy management system, which utilises sensors to continuously monitor temperature, humidity, air quality and energy consumption. This optimises the operation of the heat pump and ventilation.
  It was decided to obtain renewable energy on site—photovoltaic panels with an area of ~20 m² were installed on the roof (terrace) of the villa, hidden behind the parapet and invisible from the outside. These panels are part of a structure that conceals the existing infrastructure (GSM antennas), so they do not affect the aesthetics of the building.
  Results: The analyses conducted have demonstrated that the implementation of the aforementioned measures has resulted in a reduction of over 60% in the energy demand of the villa. This represents a substantial accomplishment, particularly in light of the constraints typically associated with historic buildings. The parameters have been brought closer to the nZEB standard applicable to new buildings, as confirmed by insulation calculations: the predicted U-value of the walls is approximately 0.30 W/m²K (previously it exceeded 1.3), the roof has been insulated to U ≈ 0.19 W/m²K, and the new windows have U ~ 0.8 W/m²K. These values meet or exceed the legal requirements for modern buildings in this region. The restoration of the villa was executed in a manner that ensured the preservation of its historic character. The exterior of the building was meticulously maintained, with facades that were meticulously restored in accordance with the original colour scheme. The interior layout was largely preserved, with the majority of new installations discreetly integrated into existing partitions. All additional elements, such as an internal lift or installations, were designed to be reversible and did not compromise the integrity of the original structure. This case exemplifies a harmonious integration of conservation and energy efficiency, underscoring the efficacy of an interdisciplinary approach in achieving substantial energy savings in a historic building while preserving its authenticity and cultural significance [76].
• Another example of good practice is the modernisation of the primary school in Olbersdorf, Saxony. This extensive complex, built in 1927–1928, is listed in the state’s register of historical monuments as an example of Weimar Republic-era school architecture. Before the modernisation, the building struggled with low insulation (walls U ≈ 1.25 W/m²K, roof U ≈ 1.52), significant heat loss, and high gas consumption for heating (~765 MWh per year, equivalent to 174.2 kWh/m² of primary energy). In summer, classrooms experienced overheating (lack of shade from the east and in the attic) and a lack of daylight (students often had to rely on artificial lighting during the day). The aim of the modernisation was to simultaneously improve learning conditions (thermal comfort in winter and summer, fresh air, better lighting, acoustics) and drastically reduce energy consumption—the aim was to achieve the 3-Litre-Haus standard, i.e., a building consuming the equivalent of 3 L of heating oil per m² per year (~34 kWh/m²). The design assumptions necessitated the implementation of innovative solutions, given that the conservator permitted only minimal insulation of the façade (maximum thickness of +6 cm). The proposal to install insulation from the interior was dismissed on the grounds of the consequential loss of valuable space and the issue of thermal bridges at the junctures between the walls and ceilings. The decision was taken to utilise a thermal insulation system on the exterior of the façade wall, employing an ultra-thin vacuum panel (VIP) system. The 2 mm-thick VIP panels (λ = 0.008 W/mK) were covered with a 3 mm layer of polyurethane foam (λ = 0.035) for protection and to level the substrate. The entirety of the structure was overlaid with a thin layer of plaster that matched the appearance of the original, historic plaster. Prior to the implementation of this solution, laboratory tests were conducted at the Bauhaus-Universität Weimar, and preliminary trials were undertaken on a section of the building’s wall. However, complications were encountered during the execution of the work. Specifically, the adhesive designed for the purpose of adhering the insulation layers to the foam failed to provide adequate adhesion, resulting in the delamination of the foam from the VIP panels. Consequently, due to technical safety imperatives, a proportion of the installed VIP panels were dismantled and substituted with an alternative material exhibiting a marginally lower lambda value.
  Notwithstanding the challenges posed by the technology employed, the project’s innovative character was maintained. It was demonstrated that even stringent conservation constraints can be satisfied through the implementation of innovative thermal insulation methods. Another significant element was the enhancement of window frames and ventilation systems. New wooden box windows (in keeping with the original form) were installed with triple thermal insulation glazing and integrated external air vents. The design of the incorporates specific apertures that facilitate the influx of fresh air-Zuluftkastenfenster. The air, initially entering the space between the outer and inner window sashes, is preheated by the incoming airflow. Subsequently, the air passes through the upper apertures in the inner sash frame, thereby entering the interior space. The integration of this solution with mechanical air extraction (exhaust fans in ventilation ducts) and a central heat recovery unit has resulted in the development of a hybrid ventilation system tailored to specific local conditions. Carbon dioxide (CO₂) sensors, installed within the building’s control system, are responsible for regulating the intensity of ventilation. In the event of an increase in concentration, the automated system initiates the activation of supplementary exhaust fans. During the summer months, this system is utilised for the purpose of night-time cooling of the building: the windows open automatically within a safe range, and fans are employed to remove heated air with efficiency, thereby enabling the interior temperature to be reduced without the need for air conditioning. Furthermore, in order to mitigate the effects of solar radiation, electrochromic windows have been installed in critical rooms. These windows are capable of darkening on demand (or automatically), thereby limiting the amount of sunlight that enters the building. In addition, slatted blinds have been installed between the window sashes, serving as an additional sun barrier. The interior lighting has been replaced with energy-efficient light-emitting diodes (LEDs) emitting a colour similar to daylight. The heat source was also replaced: the old gas boilers were replaced with a modern condensing boiler with higher efficiency (due to the existing infrastructure, it was decided to stick with gas heating, but its use was significantly reduced thanks to better insulation and heat recovery) (Figure 6).
  Results: The modernisation of the building has resulted in a multitude of benefits. The anticipated increase in energy efficiency has been demonstrated, with calculations indicating that the heat demand has been reduced to 34 kWh/m²/year (for heating and ventilation), representing an approximate 80% decrease compared to the initial state. The school has been transformed into one of the most energy-efficient historic public buildings in the region. The findings reveal a substantial enhancement in thermal comfort levels. During winter, a consistent temperature is maintained in all classrooms, leading to reduced gas consumption. In summer, the implementation of shading and night-time cooling mechanisms ensures that the classrooms do not overheat. The indoor air quality has also been found to be improved by the hybrid system, which maintains adequate levels of fresh air.

Figure 6. Primary school, Olbersdorf (Saxony, Germany). View of the façade after thermal modernisation. Source: RoesslerP, Wikipedia CC BY-SA 4.0, https://de.wikipedia.org/wiki/Datei:Olbersdorf_Schulweg_13_15.jpg, (accessed on 11 November 2025).

Figure 6. Primary school, Olbersdorf (Saxony, Germany). View of the façade after thermal modernisation. Source: RoesslerP, Wikipedia CC BY-SA 4.0, https://de.wikipedia.org/wiki/Datei:Olbersdorf_Schulweg_13_15.jpg, (accessed on 11 November 2025).

This is of crucial importance for the health and concentration of pupils. The edifice’s historic characteristics have undergone no alteration: the external insulation utilised possesses such minimal thickness that it has not impacted the façade’s appearance (architectural elements remain discernible, as 5 cm of insulation approximates the thickness of conventional plaster). The new windows have been designed to recreate the historic character of the woodwork, while also being airtight and energy efficient. The interior layout has been retained, with ventilation equipment now concealed within the existing chimney shafts and inter-ceiling spaces.

The investment in Olbersdorf demonstrated that ambitious objectives (such as the 3-litre standard) can be realised in a historic building, provided that advanced technologies are employed and comprehensive pre-implementation research is undertaken. Notwithstanding the emergence of technical complications (problems with VIP bonding—which in itself proved the reversibility of this method, as the panels could be dismantled without damaging the wall), the modernisation was considered exemplary. The final report emphasises that the school’s facilities have been significantly upgraded, leading to a substantial improvement in the level of comfort experienced by users. Additionally, the report notes a substantial reduction in heating costs, indicating that the return on investment period, though extended, is deemed acceptable in order to preserve a significant historical building for posterity. The school building in Olbersdorf has become a model for further energy renovation projects of historic schools in Germany [77,78].

5.3.1. Thin-Layer Thermal Insulation Coatings

One of the most promising innovations in the field of heritage energy modernisation is the use of thin-layer thermal insulation coatings, developed as part of ongoing research into advanced material technologies [66,67,68,71]. These coatings, based on ceramic micro-particles or nanomaterials with a high thermal reflectance coefficient, help reduce heat loss without increasing wall thickness. Their application is particularly advantageous in historic buildings, where architectural details, decorative plasterwork, or façade textures cannot be covered by traditional insulation systems.

The coating thickness typically ranges from 1 to 3 mm, allowing the original surface texture and decorative features to remain visible and intact.

Experimental studies indicate that such coatings can reduce heat losses by 15–25%, thereby improving the energy performance indicators of the building envelope [66]. An additional advantage is their vapour permeability, which maintains natural moisture diffusion through the walls—crucial for the durability of historic materials. In contrast to conventional insulation systems, which often lead to condensation and wall dampness, thin-layer thermal coatings help preserve the microclimatic balance of historic structures.

From a conservation perspective, these technologies are particularly valuable as they preserve original architectural details and minimise structural intervention. Their application aligns with the principle of minimal intervention and the concept of reversibility—the coatings can be removed if necessary, without damaging the substrate. Hence, they fully correspond to the idea of sustainable heritage renovation, combining energy performance improvements with the protection of historical and aesthetic values [66].

In the broader context of European strategies such as the Renovation Wave and the New European Bauhaus, thin-layer thermal insulation coatings represent an exemplary best practice where technological innovation is harmonised with heritage responsibility. Their inclusion in pilot schemes and EU-funded research programmes (e.g., framework program Horizon 2020) could support the development of new standards for heritage-compatible renovation.

However, the adoption of these solutions requires rigorous validation and multidisciplinary collaboration among engineers, conservators, and building physicists to ensure material compatibility and long-term energy performance stability. It would also be advisable to establish European conservation–technical guidelines for the use of thin-layer insulation coatings, supplementing the current EPBD framework with a dedicated heritage building segment.

Contemporary research in conservation and building engineering increasingly focuses on non-invasive methods that improve energy performance without compromising material authenticity or aesthetic integrity. The key challenge remains the harmonisation of EPBD technical requirements with the principles of authenticity, reversibility, and minimal intervention that are fundamental to conservation practice.

5.3.2. Reversible HVAC Systems

Modern reversible heating–cooling (HVAC) systems enable the control of temperature and relative humidity in heritage buildings without permanent intervention in walls or floor/ceiling structures. Their key advantage is reversibility—components can be dismantled or upgraded without harm to the historic fabric. Studies indicate that such systems can reduce energy use by 20–35% in large-volume buildings (e.g., churches, museums) while maintaining a stable indoor microclimate [61,69].

5.3.3. Capillary-Active and Microporous Insulations

Capillary-active materials (e.g., calcium-silicate mineral boards, lime–perlite plasters, capillary aerogels) allow diffusion-open internal insulation that does not block vapour transport through historic masonry. This approach mitigates the risk of interstitial condensation—a critical issue in the insulation of heritage walls. Research shows that such solutions can reduce heat losses by 25–40% in thick-walled buildings while preserving full “breathability” of the envelope [79].

Internal insulation systems used in historic buildings differ fundamentally in their moisture transport mechanisms, which directly influence both energy performance and long-term hygrothermal safety of the envelope. Two main categories are commonly considered: capillary-active (moisture-open) systems and vapour-tight (moisture-closed) systems.

Capillary-active internal insulation (e.g., mineral-based capillary boards, calcium silicate panels) supports bidirectional moisture transport through capillary conduction and vapour diffusion. Such systems enable moisture buffering, redistribution and enhanced drying potential, thereby reducing the risk of interstitial condensation, mould growth and freeze–thaw damage. Research by Zhao et al. demonstrates that capillary-active mineral insulation offers improved hygrothermal stability under varying indoor and outdoor conditions, making it particularly suitable for retrofitting historic buildings where maintaining material breathability and salt transport is critical [80]. These systems typically show slightly lower nominal thermal resistance compared with conventional vapour-tight systems, but their dynamic thermal performance benefits from moisture buffering effects, which contribute to a more stable indoor climate and reduced peak heating demands.

In contrast, vapour-tight internal insulation systems (e.g., systems incorporating polyethylene vapour barriers or highly impermeable foils) rely on preventing vapour ingress into the wall assembly. While these systems often provide higher thermal resistance (R-value) under laboratory conditions, their hygrothermal performance depends heavily on the perfect continuity of the vapour barrier. Even minor imperfections, perforations or ageing-related degradation can lead to condensation accumulation behind the barrier, significant moisture loads, and potential degradation of historic masonry or plaster. Studies examining climate-robust retrofit solutions highlight that vapour-tight systems may become increasingly vulnerable under future climate scenarios, where higher humidity peaks and more intense rainfall events amplify moisture stresses [81].

Overall, hygrothermal properties—moisture buffering capacity, drying potential, and condensation risk—are equally important as thermal conductivity when assessing the long-term energy performance of retrofits in historic buildings. Energy savings achieved through high thermal resistance can be undermined if the assembly accumulates moisture, leading to reduced insulation performance, thermal bridging, or material decay. Capillary-active systems, despite offering lower nominal insulation values, often result in more durable and resilient assemblies, particularly in heritage contexts where internal insulation must accommodate irregular substrates, historical materials and existing moisture loads.

5.3.4. Microconductive and Bioactive Plasters

A newer category comprises microconductive mineral plasters that combine vapour-open behaviour with passive modulation of temperature and humidity. With additives such as graphene, silver micro-particles, or nano-structured lime, these plasters improve indoor microclimate and exhibit antibacterial and antifungal properties. Pacheco-Torgal et al. report that their use can increase masonry durability by 15–20% and limit mould growth in highly damp environments [68].

5.3.5. Phase Change Materials (PCM) and Intelligent Energy Management

In heritage buildings subject to large temperature swings, there is growing use of phase change materials (PCM) together with building energy management systems (BEMS) based on environmental sensors. Their goal is to stabilise the microclimate with minimal energy demand and no alteration of the building’s form. Coupling PCM with on-site renewable sources (e.g., heat pumps) can reduce final energy demand by up to 30%, in full compliance with the principle of reversibility [82].

5.3.6. Synthesis

Low-impact technologies offer a realistic pathway to reconcile conservation and energy performance. They share three core attributes:

• Preservation of material authenticity;
• Reversibility with minimal intervention;
• Alignment with sustainability principles.

Embedding these solutions in national and EU guidance (e.g., EPBD, DSRB, Green Deal) could establish a new practice standard at the conservation–energy interface. Looking toward 2030–2050, their development is a key lever for implementing heritage-inclusive renovation strategies.

5.4. Integration of Conservation and Sustainable Development

Contemporary discourse on cultural heritage conservation increasingly emphasises the need to integrate preservation objectives with the principles of the European Green Deal and the New European Bauhaus (NEB) initiative. Both frameworks introduce a paradigm shift—treating heritage buildings not as obstacles to the energy transition but as an integral part of Europe’s sustainable future.

According to the concept of heritage-inclusive renovation strategies, modernisation efforts should respect the character, materiality, and authenticity of historic structures, while national and regional strategies are obliged to include heritage assets in their long-term renovation plans (EPBD).

A key dimension of this approach is its socio-cultural perspective: the renewal of historic buildings is not only a matter of energy efficiency but also one of quality of life, local identity, and social cohesion. In this sense, the New European Bauhaus redefines heritage as a living resource that—through the integration of beauty, sustainability, and togetherness—can actively contribute to both climate and social goals.

Local solutions and traditional materials play a crucial role in this process. Their adaptive capacity and low carbon footprint make them ideal components of climate-sensitive renovation. Their reuse—in line with the principle of “modernisation through conservation”—can significantly reduce lifecycle emissions in heritage buildings. This approach aligns with the priorities of the Renovation Wave and the European Green Deal, both of which assert that climate transformation must proceed with respect for cultural values and regional architectural diversity.

From a financial perspective, EU funding instruments such as FEnIKS, LIFE, and Horizon Europe should place greater emphasis on projects that combine energy performance improvement with heritage protection. At the same time, it is essential to establish harmonised eligibility criteria for heritage buildings within public support mechanisms.

Good practices in the thermal modernization of historic buildings:

• An example of good practice is the thermal modernisation carried out during the reconstruction of the historic House of the Riflemen’s Brotherhood in Świdwin [83]. This historic building had been stripped of its architectural decoration in previous decades. However, a high stone plinth remained. To preserve this historic element, the decision was made to insulate of the building from the inside (Figure 7).

• The revitalisation of the Kwasowo Palace demonstrates how energy efficiency measures can be successfully integrated into the conservation of historic buildings through participatory governance and EU-funded regional programmes [84,85]. The project illustrates the potential of combining technical renovation with social activation, showing that heritage preservation and climate objectives can be mutually reinforcing when local authorities, residents, and community organisations collaborate within a shared framework of sustainable development (

  Table 8. Examples of comprehensive thermal modernisation of historic palaces in Poland. Author: Izabela Kozłowska.

  Facility (Location)	Scope and Objectives of Activities	Partners and Financing	Effects and Significance
  Palace in Kwasowo (Sławno commune, West Pomeranian Voivodeship, Poland) [84,85]	Comprehensive revitalization and thermal modernisation of a historic building: basement waterproofing, roof replacement, attic ceiling and wall insulation, woodwork replacement, stairwell renovation, lightning protection system, and entrance reconstruction. The goal was to improve energy efficiency while preserving historical values and activating the local community.	Sławno Commune (coordination and supervision), Wybrzeże Housing Cooperative (manager), Kwasowo Palace Association (social partner). Financing: 85% EU funds as part of the revitalization project (PLN 1.53 million), 15% residents’ own contribution.	Improving energy efficiency and user comfort, protecting historic buildings, activating residents, and increasing public awareness of the value of heritage. This is an example of effective collaboration between local government, non-governmental organisations, and the community.
  Bukowiec Palace (Lower Silesia, Poland) [86,87,88]	Comprehensive energy retrofit of a 16th-century palace. The building is listed in the register of monuments. The energy audit before renovation indicated a primary energy demand (EP) of ~650 kWh/m2 per year. The project included roof and wall insulation, replacement of windows and doors, and modernisation of the heating system. Renewable technologies were integrated: a 26.4 kWp photovoltaic installation (roof and ground-mounted), a 13.6 kWh energy storage system, and a 110 kW ground-source heat pump supported by 16 geothermal probes. A Building Management System (BMS) was implemented for intelligent energy control. The facade was covered with 3 cm thick aerogel thermal insulation plasters.	General contractor: Pre-Fabrykat Ltd.; close cooperation with the heritage conservator and the project architect. Funding: regional and national heritage-energy programmes (public support combined with private investment).	Primary energy demand (EP) reduced by ~90%, from ~650 kWh/m2 year to ~74.3 kWh/m2 year. The palace became energy-efficient and environmentally friendly while maintaining its historical character. The project demonstrates the synergy between cutting-edge renewable technologies and cultural heritage preservation—a model example of deep energy retrofit in a listed monument.

  ; Figure 8).

• Another example of good practice is the comprehensive thermal modernisation carried out in a 16th-century palace in Bukowiec [86,87,88]. A pre-investment energy audit revealed an EP (primary energy) index of ~650 kWh/m² per year. Thanks to the comprehensive thermal modernisation, which included replacing windows and doors, insulating the roof and external walls, and modernising the heating system, the EP index was reduced by nearly 90% to approximately 74.3 kWh/m² per year. To further improve efficiency, modern, ecological solutions were implemented. The facade of the palace was finished with a 3 cm thick thermally insulating gel plaster. A 26.4 kWp photovoltaic system was installed (panels were placed on the ground and roof of the extension), along with a 13.6 kWh energy storage system and a BMS system for intelligent energy management. A 110 kW ground-source heat pump, working with 16 geothermal probes, was used to heat the building. The renovated Bukowiec Palace has become energy-efficient and environmentally friendly, while retaining its historic character. The investment is a prime example of combining modern technologies (such as heat pumps, photovoltaics, and energy storage) with care for the building’s historic heritage (Table 8; Figure 9).

5.5. Implementation Challenges and the Role of Heritage Authorities

Despite the theoretical coherence between heritage-inclusive renovation strategies and EU policies, their implementation faces numerous institutional and technical barriers. The most frequently cited challenges include:

• The absence of a common methodology for assessing the outcomes of heritage modernisations, including a lack of measurable Key Performance Indicators (KPIs) under the EPBD;
• The conflict between authenticity and energy efficiency, which often leads to the rejection of innovative technical solutions;
• Limited access to dedicated funding, as mainstream programmes such as Clean Air do not account for the specific requirements of protected buildings;
• Insufficient collaboration between conservators and energy engineers, which hampers the development of integrated, sustainable design concepts;
• The lack of climate-risk assessment tools for heritage assets, restricting long-term adaptation planning.

Scholars and international organisations—including Europa Nostra, ICOMOS, and experts of the European Commission—highlight the need to develop integrated methodological guidelines for the renovation of historic buildings within the context of the EPBD and national strategies. They recommend that future frameworks should:

• Harmonise definitions and eligibility criteria for heritage assets in modernisation funds;
• Introduce a heritage-energy audit as a standard assessment tool;
• Promote low-invasive technologies, such as thin-layer thermal coatings, reversible HVAC systems, and intelligent microclimate control;
• Incorporate educational and awareness-raising components, in line with the values of the New European Bauhaus.

In this context, the principle of heritage-inclusive renovation strategies marks a paradigm shift: from treating heritage buildings as exceptions (EPBD 2010–2012) to recognising them as active resources within the energy transition (Green Deal, NEB).

However, the effectiveness of this approach depends on the development of monitoring tools and comparative metrics for evaluating renovation outcomes in heritage buildings, as well as on the institutional inclusion of heritage supervision within the assessment of energy modernisation projects.

5.6. Directions for Further Research

Future research should focus on the following key areas:

• Evaluating the effectiveness of various types of energy interventions in heritage buildings, taking into account their impact on indoor microclimate, material durability, and authenticity;
• Developing energy efficiency indicators integrated with conservation criteria, which could be incorporated into European renovation strategies;
• Expanding empirical databases (e.g., NID, GKZ, NFOŚiGW) to enable statistical analysis of modernisation outcomes at the regional level;
• Modelling cost–benefit scenarios for heritage building modernisation toward 2050, based on data concerning material lifespan, carbon footprint, and operational efficiency;
• Investigating social and perceptual aspects—how modernisation affects local identity, the aesthetic quality of historic spaces, and user well-being.

Incorporating these elements into future analyses could support the development of a coherent heritage-inclusive renovation framework, one that not only aligns with EU policies but is also evidence-based and integrated with conservation practice.

6. Conclusions

The analysis of EU and Polish strategic documents from 2005 to 2025 reveals a clear trend toward integrating energy–climate policy with cultural heritage protection. The initial dichotomy—where energy regulations exempted heritage buildings from efficiency requirements while conservation strategies ignored energy performance—has gradually evolved into a holistic and integrative approach.

Over this twenty-year period, both the European Union and Poland underwent a significant transformation in their approach to energy modernisation of historic buildings—from the phase of exemptions and rigid conservation protection (EPBD 2010, EED 2012) to an integrated model in which cultural heritage is regarded as an active component of the green transition (Green Deal, NEB).

Key findings include:

• Evolution of legal and policy frameworks.
  The shift from exclusionary conservation clauses to integrated objectives of protection and efficiency has led to the emergence of a new heritage management model. Responding to EU policy shifts, Poland has developed strategic documents (PEP2040, DSRB, KPEiK) that for the first time explicitly included historic buildings in national renovation planning;
• Empirical component—the modernisation gap.
  The analysis of indicators W1–W12 shows that heritage assets constitute only about 0.3–0.5% of all energy efficiency and retrofit projects. Despite the existence of regulatory and financial frameworks, practical implementation remains limited, with a persistent lack of dedicated funding instruments and monitoring systems for the heritage sector;
• Growing importance of conservation guidelines and soft instruments.
  The Guidelines of the General Conservator of Monuments (2020) and initiatives such as the New European Bauhaus have begun introducing cultural values into energy policy discourse. However, their influence remains constrained due to the absence of legally binding status;
• Need for methodological integration and a conservation–energy audit.
  The lack of standardised efficiency indicators for heritage buildings hinders data comparability. It is recommended to develop integrated assessment tools combining energy performance metrics with evaluations of authenticity, materiality, and microclimate;
• The concept of “heritage-inclusive renovation strategies.”
  Implementing sustainable development principles in heritage conservation requires an approach that acknowledges the historical identity, aesthetic, and social dimensions of buildings. Only by integrating heritage assets into long-term renovation strategies—supported by EU funding instruments such as FEnIKS, LIFE, and Horizon Europe—can coherence between cultural and climate goals be achieved.

The findings of this study demonstrate that improving the energy performance of historic buildings requires a multi-layered approach that integrates technical feasibility, conservation constraints, and long-term hygrothermal safety. While the analysis highlights significant progress in aligning Polish and EU policy frameworks, it also reveals the need for more coherent, data-driven and interdisciplinary practices to ensure that energy retrofits in heritage buildings are both effective and culturally responsible. Building on these insights, the following recommendations propose concrete, actionable steps that can support policymakers, conservation authorities, and practitioners in developing sustainable and evidence-based renovation strategies.

Develop a centralised monitoring system for energy retrofits in heritage buildings.

A national, harmonised monitoring platform—based on comparable energy, humidity, and conservation indicators—would enable systematic data collection, assessment of long-term performance, identification of best practices, and early detection of retrofit-related risks. Such a system would improve transparency and support evidence-based decision-making across institutions:

• Integrate low-impact materials and reversible solutions into Polish technical standards and heritage guidelines.
  Insights from EU projects such as RIBuild and HEROMAT show that capillary-active, vapour-open, mineral and reversible insulation materials enhance hygrothermal safety while reducing the environmental footprint of retrofits. Their formal inclusion in national standards would facilitate the adoption of solutions consistent with conservation principles and sustainable renovation goals;

• Establish cross-sectoral training programmes for conservators, engineers and policymakers.
  Effective energy retrofitting of heritage buildings requires close collaboration among building physicists, conservation specialists, architects, and public authorities. Training programmes—modelled on initiatives like Climate2Preserv—should strengthen shared understanding of hygrothermal risks, EU regulatory frameworks, and methods for assessing material durability in historic envelopes;

• Encourage cross-border participation in EU research projects to fill empirical data gaps.
  Current knowledge gaps—such as limited datasets for hygrothermal modelling, insufficient validation of internal insulation systems under diverse climates, and a lack of long-term monitoring—can be effectively addressed through active involvement of Polish institutions in EU-funded research. Participation in initiatives like empirical HAM round-robin validations would support methodological robustness and improve national retrofit strategies.

In conclusion, this study demonstrates that heritage protection and energy transition need not be in conflict—on the contrary, they can mutually reinforce each other through the creation of inclusive, interdisciplinary, and evidence-based policies.

Future research should prioritise the quantitative evaluation of modernisation outcomes and the development of European databases that allow for cross-country comparison of results, providing a foundation for a truly integrated model of sustainable heritage management.