GENERAL INFORMATION

Ravne na Koroškem

Intervention year: 2025

Area of intervention: Retrofit

Scope: Research

Technology maturity level: Project

Climate zone: Cfb - Temperate oceanic climate

Ob Suhi 19, Ravne na Koroškem, Slovenia

Architect

Eutrip d.o.o.
Owner

Stanovanjsko podjetje

Intervention year: 2025

Area of intervention: Retrofit

Scope: Research

Technology maturity level: Project

Architect

Eutrip d.o.o.
Owner

Stanovanjsko podjetje

This medium size building is a multi-use building, single owner, built in 1982. It is composed by 71 small residential units (singles, couples and families), and some offices in the ground floor. The buildings are part of a bigger complex of “line building”. At the ground floor there are some offices, four residential floors and on the top an attic area with reduced height (before renovation). The structural part of the building is steel-reinforced concrete frame with bricks masonry as perimeter walls. Both building are connected to a district heating, poor envelope and windows performances.

The window-to-wall ratio is 20% in the existing building, 22% in the new floor.

Building sector

Residential

Building use

Multi-family building

Heated floor area

2836 m²

Façade area

Prefab: 169 m² | ETICS: 1080 m² | New floor: 379 m²

Building height

High rise (> 4 storeys)

Interstorey height

2.7

Existing building structure

Reinforced concrete

Existing wall stratigraphy

Internal plaster, hollow modular brick, PVC foil, XPS, silicat brick

Total renovated façade surface (industrialised and not industrialised)

Prefab + New floor: 1249 m²

Percentage of renovated façade with industrialised approach

14 %

Window to wall ratio

20 %

U-value existing windows

1,5 W/m2k

U-value existing façade

0.545

U-value after renovation

Existing part ETICS: 0.104 W/m2k | Prefab: 0.11 W/m2k | New floor: 0.107 W/m2k W/m2k

Energy concept

The renovation combines industrialised envelope solutions with an upgraded energy system and the addition of a new floor: this is an example of densification in Slovenia. During the renovation, thermal insulation was improved on all façades and on the roof.

One façade was renovated using a prefabricated INFINITE façade, while the remaining façades were insulated using ETICS (External Thermal Insulation Composite System), partly complemented by the INFINITE passive kit.

On the south façade, INFINITE’s all‑industrialised BIPV kit was installed, while traditional PV was placed on the roof. Heating and domestic hot water are mainly supplied by heat pumps.

A air-to-water heat pump provides heating and DHW, while the existing district heating network is used as backup or during periods of very low outdoor temperatures. An additional heat pump installed on the roof serves the new floor.

The roof‑mounted PV system is sized to cover the electricity demand of the heat pumps. 6 square meters of green living wall system has been implemented in the upper floor close to a south terrace. The small portion of green solution can be an added value to the tenants living the apartment in term of aesthetics and micro-clima during the summer seasons.

BEFORE RENOVATION

Technology solution sets	Type of system	Generation	Distribution
Heating system	Centralized	District heating	Radiator
Domestic hot water	Centralized	Not integrated with the heating system (Electric boiler)

AFTER RENOVATION

Technology solution sets	Type of system	Generation	Distribution
Heating system	Centralized	Air source heat pump District heating	Radiant floor (new floor only) Air (new floor only) Radiator (old building)
Cooling system	Centralized	Air source heat pump / Reversible Chiller	Air
Mechanical ventilation	Decentralized Centralized	Balanced mechanical ventilation with heat recovery at building/apartment/room level	Air ducts
Domestic hot water	Centralized	Integrated with the heating system

Integrated technologies

A new additional floor was built using INFINITE industrialised façade and roof systems. This added floor integrates several INFINITE technologies:

- a distribution kit providing heating, cooling and fresh air to the apartments,

- smart (electrochromic) windows,

- BIPV modules on the façade,

- and the green kit.

Mechanical ventilation

In the new floor, indoor comfort is ensured through radiant floor heating combined with warm air heating and ventilation units integrated into the walls. Four of the six new apartments on the upper floor are equipped with VMCs (Mechanical Ventilation Unit from Vortice) and the related distribution elements, providing heating, cooling and continuous air renewal at apartment level.

In addition, a centralised VMC has been integrated into the living room areas to ensure adequate fresh‑air supply in larger spaces, complementing the apartment‑level units and supporting indoor comfort throughout the new floor.

VORTICE, the producer of the ventilation machine, did some performance and fluid dynamics simulations for integration of the machine for the new floor.

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BIPV

The BIPV system is installed on the façade of the existing building, primarily on the southern exposure, and is fully integrated into the prefabricated INFINITE façade panels. Rather than being added as a separate system, the photovoltaic modules replace conventional cladding elements, fulfilling both protective and energy‑generating functions.

In total, 317.67 m² of glass‑glass BIPV modules have been installed on the south façade, partly on the existing building and partly on the newly added floor. The façade uses glass‑glass BIPV modules (mostly standard, some custom) with a uniform white/coloured finish, specifically selected to ensure architectural coherence and visual continuity with the rest of the building envelope.

The modules are mounted using an industrialised hybrid fixation system, which allows BIPV elements to be installed in a way comparable to traditional façade cladding. This approach reduces on‑site installation time and complexity, while supporting high‑quality integration of renewable energy generation within an industrialised deep renovation process.

Smart windows

The NextSense module and control hub has been implemented to control the external venitian blind on the upper floor. The Sense bar installed on the windows are providing data to the control HUB that move the shading system based on algorithem to optimize solar gain/shadings

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Green façade

Six square meters of green living wall system has been implemented in the upper floor close to a south terrace. The small portion of green solution can be an added value to the tenants living the apartment in term of aesthetics and micro-clima during the summer seasons.

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Envelope technology

Prefabricated envelope technology

INFINITE all-industrialised BIPV Kit

The prefabricated BIPV kit is conceived as a plug‑and‑build solution, compatible with both the renovation of existing façades and the construction of additional floors.
The solution is designed and manufactured off‑site and installed on the building with limited disruption to occupants.
The integrated solution is based on timber‑based prefabricated façade elements, composed by a wooden-based frame with mineral wool as insulation layer to enhance the insulation capacity of the building.

External finishing

Ventilated cavity

Main structure

Insulation

Compensation layer

Anchoring element

Joints

Tolerances

Circularity

Ease of disassembly (system level)
Ease of reuse
Ease of recycling (component level)

Materials origin
Material use efficiency / Waste produced during production of the technol
Circularity certification

General Data

Max panel width

Max panel height

Panel Weight

kN/m²

Panel thickness

Performance

U-value

Acoustic resistance

Fire resistance

Seismic

Water/Air tightness

Certifications and tests

Simulation campaign

Tests

CE mark / type of certificate

Prefabricated roof technology

All new floor was manufactured in the Žiher factory and walls and roof were assembled on site. The roof is covered with photovoltaics panels.

Design and Installation

Construction process

The construction process was done in three main phases applying three different approaches, besides the finishing part done at the latest moment.

1. demolition of the roof and then the installation of the new prefabricated wooden-based structure with Vortice units and smart windows on the top floor, following the densification approach with the IDR

2. installation of the prefabricated façade on part of the south façade with a movable crane, and retrofitting the existing building

3. finalize the rest of the existing building with a standard ETICS.

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Auxiliary elements (i.e. scaffolding)

Yes

Works on balconies

Standard retrofit of the balconies

Works on roof

Demolition and reconstruction

Interaction with the existing structure

Just compensation layer and windows interface

Interaction with existing facilities

Level of disturbance

Medium, due to drilling the anchoring in several points

Installation time

m²/day

Methodology used for the audit and survey: The pre‑design phase was a key moment in defining the overall renovation strategy. A series of audits and targeted analyses made it possible to explore different renovation scenarios and assess their feasibility. A decisive input came from the structural analysis, which confirmed that the existing building could bear additional loads. This result opened the possibility of adding a new floor, significantly expanding the scope of the intervention. In parallel, the municipality was actively involved to verify the regulatory feasibility of increasing both the building height and volume. This iterative process led to the definition and comparison of several options. Among them, a densification strategy combined with an industrialised deep renovation (IDR) of the existing building was selected as the most promising solution. At this stage, a first cost estimation and return‑on‑investment assessment were also carried out to support decision‑making.

Digitalization of the pre-design phase: A laser scan survey was carried out at the beginning of the project to obtain accurate geometric data through a point‑cloud model of the existing building. Based on this dataset, a BIM model was developed and used as the reference for design and coordination. Due to the research‑driven nature of the project, the design process was highly iterative. Multiple renovation scenarios were developed and simulated, as new information progressively emerged and boundary conditions evolved. The BIM environment played a key role in supporting this process, allowing the team to test alternative solutions and adapt the design accordingly. A significant challenge arose when a key technology provider withdrew from the project during the development phase. This required the consortium to identify and integrate local alternative solutions, ensuring continuity of the renovation while maintaining alignment with the project’s technical objectives.

Digitalization of the design phase of the façade: The design process involved multiple stakeholders and project partners, following an integrative and participatory approach. The main design activities were led by EUTRIP, drawing on its multidisciplinary expertise in architectural and construction design. Technology partners of the INFINITE project were subsequently engaged to support the detailed design phase, contributing specialist knowledge to ensure the correct integration of the project’s industrialised envelope and energy solutions. Eurac Research and the Institute for Innovation and Development of the University of Ljubljana supported the entire process by providing technical evaluations, performance assessments, and by facilitating coordination among all actors involved. Bouygues Construction, acting as implementation leader, oversaw the overall process through a general technical and operational review, ensuring consistency between design decisions and implementation requirements. The process concluded with the preparation of a comprehensive design package, including architectural renderings, technical drawings, and a detailed cost estimation. These documents were used to engage a local general contractor, who submitted a formal offer and was subsequently awarded the project.

Digital compatibility of data between design and manufacturing phase: Not available

Prefabrication at component level: During the manufacturing phase, the ETICS component was installed on site using a traditional construction approach. In contrast, the other two solutions—the industrialised deep renovation of the existing building and the densification through the addition of a new floor—were produced off site by two specialised companies. The industrialised deep renovation of the existing façade was carried out by Lesoteka, while the densification works and related activities were handled by Ziher Group. Overall, the manufacturing process progressed smoothly. This was partly due to the support of the INFINITE project partners—most notably Vortice, which contributed by supplying materials and ventilation units. Both industrialised renovation solutions were fully prefabricated in the factory, with the exception of the external cladding, mainly consisting of building‑integrated photovoltaics, which was completed on site.

Prefabrication at whole-facade level: Not Available

Transport typology to building site (any additional equipment needed): Trucks and a dedicated larger crane for transport.

Distance from the production site to the building site: Lesoteka: 28 km | Ziher: 125 km

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Performance and energy savings

Use stage

Measurements are ongoing

	Before renovation	After renovation
Primary energy demand (total building consumption)	n/a	n/a
Energy demand for HEATING	n/a	n/a
Energy demand for COOLING	n/a	n/a
Energy consumption for HEATING	150 MWh/a	50 MWh/a
Energy consumption for COOLING	n/a	n/a
Energy consumption for domestic hot water	n/a	n/a
Thermal comfort	n/a	n/a

Pre-renovation monitored data availability

Measurements ongoing

Renewable energy production after renovation

n/a

Primary energy savings

n/a

LCC

Measurements are ongoing

Product / technology cost

n/a

Construction / installation costs

n/a

Maintenance

n/a

Operation

n/a

Replacement

n/a

End of life

n/a

Payback period

n/a

LCA

Measurements are ongoing

Technology impact

n/a

Product and construction stage (A1-A5)

n/a

Use stage (B1-B5)

n/a

Operational energy (B6)

n/a

End of life (C1-C4)

n/a

Benefits and loads beyond the system boundary (D)

n/a

Cultural and climatic aspects

This building was historically known as a “singles home”, originally used to accommodate workers employed at the nearby steel factory. Over time, and prior to renovation, the building acquired a negative reputation and was often perceived as a socially marginalised housing complex. In parallel, it also served, and continues to serve, as temporary accommodation for vulnerable groups, such as people who have lost their housing (for example single mothers).

This role is coordinated in close cooperation with the municipality, the social care centre and STAN, the local housing organisation. The renovation strategy deliberately addressed not only technical performance, but also the social perception and role of the building.

By combining deep renovation with densification, and by adding a new floor with higher‑quality apartments, the intervention improved the overall image of the building without triggering displacement or social exclusion. Rather than leading to gentrification, the project helped stabilise the social mix and improve living conditions for existing residents.

Interviews and post‑renovation surveys show a significant increase in resident satisfaction. Indoor Environmental Quality (IEQ) assessments confirm this trend quantitatively. When compared to the weighted PRE‑renovation baseline, POST‑renovation results show substantial improvements across all key IEQ indicators.

Importantly, a comparison between equivalent seasons (winter PRE3, December 2022, and winter POST, January 2026) demonstrates that these improvements are not attributable to seasonal variation.

Fully acceptable temperature ratings increased from 29.2% to 76.7%, indicating a major improvement in thermal comfort.
Dissatisfaction with indoor air quality dropped from 34.6% to 0%, effectively eliminating unacceptable IAQ ratings.
In addition, the share of residents reporting at least moderate odour presence decreased from 26.9% to 13.3%.

This winter‑to‑winter comparison strongly supports the conclusion that the observed improvements are a direct result of the renovation.

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Ravne na Koroškem

Energy concept

BEFORE RENOVATION

AFTER RENOVATION

Integrated technologies

Mechanical ventilation

BIPV

Smart windows

Green façade

Prefabricated envelope technology

INFINITE all-industrialised BIPV Kit

Circularity

General Data

Performance

Certifications and tests

Prefabricated roof technology

Construction process

Use stage

LCC

LCA

Cultural and climatic aspects

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