Introduction

The Citizen-led Renovation (CLR) initiative has emerged as a key approach for engaging communities in the energy transition, placing citizens at the centre of decision-making and implementation processes. At the same time, the revised Energy Performance of Buildings Directive (EU) 2024/1275 establishes an accelerated trajectory for improving the performance of Europe’s building stock, while recent European Commission guidance further emphasises the need for structured and scalable frameworks capable of delivering measurable outcomes across Member States.

In practice, building professionals and local authorities are often confronted with fragmented interventions, limited technical guidance, and a lack of structured pathways that support coherent renovation strategies. This implementation gap continues to constrain the effectiveness and replicability of citizen-led approaches.

Phase II of the Citizen-led Renovation initiative addresses this challenge by developing typology-based renovation guidelines, structured intervention pathways, and locally adaptable frameworks. Drawing from pilot cases in Hungary and the province of Girona (Spain), the initiative demonstrates how renovation strategies can be standardised while remaining responsive to local building characteristics, combining technical solutions with social and digital dimensions. 

Building on these results, the next phase is to scale up by establishing a network of 11 organisations (‘enablers’), such as Regional and Local Energy Agencies, cooperatives, and associations, to support widespread citizen-led renovation. With a broader infrastructure and an expanded support network, CLR Phase III aims to empower more citizens and energy communities to drive the transition toward energy-efficient and resilient buildings across Europe. 

Technical frameworks for citizen-led renovation: evidence from Phase II implementation
 

Typology-based renovation as a scaling mechanism

The delivery of large-scale renovation programmes requires technically robust, standardised, and locally adaptable guidance capable of ensuring consistent performance outcomes across diverse building stocks. In practice, the absence of such structured frameworks has resulted in fragmented interventions, limited energy savings, and reduced scalability of renovation efforts.

Phase II of the Citizen-led Renovation initiative addresses this gap through the development of three core technical documents:

I. A typology-based renovation guide for the Hungarian residential building stock

II. A multi-typology retrofitting guideline for the Province of Girona

III. An Energy Masterplan supporting the operationalisation of an energy community in Sant Joan de les Abadesses.

These documents form a coherent methodological framework linking building-level interventions, neighbourhood-scale planning, and community-level energy system integration. Their combined contribution lies in the definition of structured renovation pathways, the standardisation of technical solutions, and the provision of quantifiable performance and cost benchmarks that can support replication across different regional contexts.

Typology-based renovation guidelines: the Hungarian case

The Hungarian renovation guide focuses on the ‘Kádár-kocka’ typology, a detached single-family house representing a substantial share of the national housing stock. The technical approach is based on the definition of a reference building (approximately 100 m² heated floor area), enabling the standardisation of intervention measures, cost estimation, and performance assessment. 
 

_{Figure 1. The Kádár-kocka.}

The initial condition of this typology is characterised by envelope performance significantly below current regulatory thresholds. External walls typically exhibit U-values in the range of 1.3–1.5 W/m²K, windows exceed 2.4 W/m²K, and attic elements are often uninsulated. Air leakage rates are high, and heating systems are frequently outdated and poorly controlled. These characteristics result in high energy demand and low thermal comfort.
 

_{Figure 2. Typical floor plans of the Kádár-kocka House. Source}

The guide introduces a structured classification of renovation interventions into light, medium, and deep pathways, each defined through explicit technical specifications.

The light renovation pathway prioritises interventions with high cost-effectiveness and low implementation complexity. The insulation of the attic slab is identified as the primary measure, with recommended insulation thicknesses of 20–30 cm, achieving U-values in the range of 0.13–0.22 W/m²K. This intervention alone can reduce heat losses through the roof by up to 80–90%, with total energy demand reductions of approximately 10–25%. Additional measures include airtightness improvements and optimisation of heating system control. 

The medium renovation pathway introduces a coordinated package addressing all major transmission losses. External wall insulation is applied to achieve U-values aligned with national regulatory thresholds (approximately 0.24 W/m²K), while windows are replaced with units below 1.10 W/m²K. Heating systems are adjusted or replaced to match the reduced heat demand, ensuring system efficiency and avoiding oversizing. This pathway typically delivers energy demand reductions in the range of 40–60%.

The deep renovation pathway corresponds to a whole-building intervention, addressing the envelope, technical systems, and indoor environmental conditions in an integrated manner. As presented in Table 1, external walls are typically insulated with 15–20 cm insulation layers, achieving U-values below 0.20 W/m²K, while roof elements are upgraded to approximately 0.13–0.17 W/m²K. High-performance windows (Uw ≤ 1.0–1.1 W/m²K) are installed with full airtightness treatment and thermal bridge correction. Heating systems are replaced with air-to-water heat pumps, combined with system reconfiguration where required, and mechanical ventilation with heat recovery is introduced to ensure controlled indoor air quality.

Indicative investment levels for deep renovation of the Kádár-kocka typology typically range between approximately €18,000 and €30,000 per dwelling, depending on system configuration, the level of envelope upgrade, and the inclusion of renewable energy systems. Photovoltaic installations further increase the total investment but contribute to reducing operational energy costs and supporting electrification.
 

_{Table 1. Indicative per-building costs for deep renovation.}

The deep renovation pathway requires alignment with available financial instruments and local support mechanisms, given its higher investment intensity. In the Hungarian context, the feasibility of such interventions is strongly influenced by the combination of national programmes and locally facilitated support structures. For the Kádár-kocka typology in municipalities such as Alsómocsolád, medium and deep renovation packages can be effectively supported through schemes such as the Energetikai Otthonfelújítási Program, which requires a minimum 30% primary energy reduction and provides combined grant and interest-free loan support. Additional programmes, including the Vidéki Otthonfelújítási Program, provide partial co-financing, particularly for light and medium interventions, with eligibility conditions favouring smaller rural municipalities.

The combined effect of financial incentives and local facilitation creates a practical implementation framework, allowing renovation pathways to be matched with household capacity and progressively deployed across the building stock.
 

_{Table 2. Indicative support mechanisms and relevance for Kádár-kocka renovation in Alsómocsolád.}

Multi-typology retrofitting guidelines: the Girona case

The Girona retrofitting guidelines extend the typology-based approach to a more heterogeneous building stock, characterised by a combination of social housing, historic buildings, and multi-family residential blocks. 

Three representative typologies are analysed:

I.  post-war social housing from the 1950s,

II.  traditional buildings in historic town centres, and

III.  multi-family residential blocks constructed during the 1960s and 1970s.

Each typology is examined in terms of construction characteristics, envelope performance, and typical deficiencies. Common issues include uninsulated masonry walls, single-glazed openings, uncontrolled ventilation through attic cavities, and significant thermal bridging at structural junctions.

The 1950s social housing typology is characterised by repetitive low-rise structures with uninsulated ceramic envelopes, high air permeability, and significant transmission losses. 
 

_{Figure 3. Aerial view of the Sant Narcís neighbourhood, primarily constructed based on this housing typology (1980-2000). Source}

Retrofitting strategies focus on external insulation (10–12 cm SATE systems), window replacement (Uw < 1.3 W/m²K), and roof insulation through attic cavities, achieving substantial reductions in heat losses with limited structural intervention.
 

_{Figure 4. Axonometric Section presenting the insulation of a double brick wall with an air-socket. Source: IEECP.}

Historic buildings in town centres present a fundamentally different constraint set, driven by heritage protection and the hygrothermal behaviour of thick masonry walls (50–70 cm). External insulation is generally not feasible; therefore, internal insulation systems (5–8 cm vapour-permeable materials), lime-based façade restoration, and moisture control measures such as ventilated slabs are prioritised. Energy demand in these buildings frequently exceeds 180 kWh/m²·year, requiring careful balancing between performance improvement and material compatibility. 
 

_{Figure 5. Signature historic facades in Girona city centre. Restoring traditional window shades can allow 
for monitoring internal shade and temperature while preserving the building’s unique identity. Source}

Multi-family residential blocks from the 1960s–1970s exhibit standardised construction with uninsulated façades (U-values >1.5 W/m²K), flat roofs without insulation, and significant thermal bridging at slab edges and balconies. Retrofitting strategies are based on external insulation systems (8–12 cm), roof refurbishment with inverted insulation layers, and the introduction of collective systems, including centralised heat pumps and shared photovoltaic installations.
 

_{Figure 6. Residential building in the Font de la Pólvora neighbourhood. Source}

Across all typologies, system-level interventions include electrification of heating (SPF > 3), integration of photovoltaic systems, and deployment of monitoring tools to support performance verification and operational optimisation.

The guidelines are complemented by detailed cost ranges and locally available financial instruments, including regional subsidy schemes, tax incentives, and energy savings certification mechanisms. This combination of typology-specific technical solutions and financing structures enables the alignment of renovation pathways with both building characteristics and household capacity, supporting practical implementation at scale.

Energy Masterplan: integrating buildings with local energy systems in Sant Joan de les Abadesses

_{Figure 7. Sant Joanina Energy Community.}

The Energy Masterplan developed for the Sant Joanina Energy Community extends the scope of renovation from individual buildings to the local energy system level. 

The Masterplan is based on a detailed assessment of local energy demand, including residential heating (approximately 15–16 GWh annually), electricity consumption (approximately 5.1–5.6 GWh), and mobility-related energy use (as highlighted in Table 1). These data provide the basis for the design of an integrated energy system combining demand-side measures and local renewable generation.
 

_{Table 3. Local residential energy demand.}

The current implementation includes photovoltaic installations with a total capacity exceeding 100 kWp, generating approximately 147 MWh annually. While this represents a limited share of total municipal demand, it establishes a functional baseline for community-scale energy production.

The technical framework defines a layered system architecture. The first layer consists of collective self-consumption based on distributed photovoltaic systems. The second layer introduces digital management platforms for monitoring generation and consumption. Subsequent layers include the integration of storage systems, electric vehicle infrastructure, and the progressive electrification of heating through building renovation.

A key contribution of the Masterplan is the explicit linkage between building renovation and energy system optimisation. The document identifies building retrofitting as a necessary condition for reducing thermal demand and enabling the efficient operation of electrified systems such as heat pumps. This integrated approach aligns with the EPBD emphasis on the decarbonisation of both buildings and energy systems.

The Masterplan also defines governance and financing mechanisms, including cooperative structures, public-private partnerships, and phased investment strategies, as showcased in Table 4 and Figure 8. These elements support the long-term viability and scalability of the energy community model.

_{Table 4. Available National and Regional financing initiatives.}

_{Figure 8. Crowdfunding for Citizen-led renovation.}

CLR Phase III: growing a Europe-wide movement

Phase III of the Citizen-Led Renovation initiative marks a shift from pilot actions to large-scale implementation, focusing on expanding support structures across Europe. A network of 11 enablers has been established to provide tailored technical, financial, and organisational assistance to citizen-led renovation efforts.

These enablers are distributed across several countries, including Italy, Ireland, Spain, Croatia, France, Belgium, the Netherlands, Greece, and Estonia. They act as facilitators, helping local actors -such as energy communities and homeowners' associations- organise, finance, and implement renovation projects while strengthening local ecosystems for community-led action.

Each enabler supports at least three energy communities or associations, referred to as ‘collectives’. These collectives will develop concrete renovation projects, often based on collaborative models such as buying clubs, shared technical services, or joint access to financing.

By the end of the initiative, this structure is expected to support a minimum of 33 collectives, all of which will have undertaken renovations aimed at improving energy efficiency in residential buildings. Through this scaling approach, Phase III aims to replicate successful local initiatives, accelerate decarbonisation, and place citizens at the centre of Europe’s Renovation Wave.

Conclusions

Phase II of the Citizen-led Renovation initiative demonstrates that typology-based approaches can deliver structured, technically consistent renovation frameworks supported by quantified performance and cost benchmarks. The integration of building-level interventions with community-scale energy planning strengthens implementation relevance. The inclusion of financing mechanisms further aligns technical solutions with real conditions. As reflected in the European Commission guidance, Phase III will focus on scaling, replication, and strengthening local implementation ecosystems. Building on Phase II, the next phase aims to enable systematic deployment of technically robust and operationally viable renovation pathways across diverse regional contexts.