Motivation and research question

Decarbonization of the building sector plays a central role in achieving climate neutrality.
In Klagenfurt and throughout Carinthia, the conventional method of demolition/new construction ("reconstructing") has been used to date when dealing with existing residential buildings. The disadvantages of this method are that, compared to a complete renovation, it consumes about 4.5 times more raw materials, causes about 4.5 times more waste, and generates more than three times as many CO₂e emissions. In addition, this method also leads to the migration of residents and thus to a failure to achieve social accuracy. This approach – demolition/new construction ("reconstructing") – is based on traditional ways of thinking and acting and reproduces the linear economy with all its negative consequences for the climate and society.

On the way to achieving the climate targets – EU 2050, Austria 2040, and Klagenfurt 2030 – a paradigm shift is absolutely and urgently necessary, especially in the construction industry, as globally it accounts for 50% of resources, 36% of total waste, and 37% of CO₂e emissions.
Making a fundamental contribution to changing this global situation locally and effectively was the main motivation for this feasibility study.

The research question was whether the previously linear economic approach to existing residential areas could be replaced by a holistic approach and process culture, leading to more ecologically, socially, and economically sustainable results and thus making a significant contribution to achieving the climate goals of the city of Klagenfurt.

The Dag Hammarskjöld residental area – a city-owned housing estate with 200 residential units from the early 1960s in the Waidmannsdorf district of Klagenfurt, which has been in need of renovation for some time and has the lowest rents in subsidized housing. The aim was to carry out the first-ever renovation of a large-scale residential quarter, especially in the affordable housing segment, instead of conventional demolition/new construction ("reconstructing").

Initial situation/status quo

The provincial capital city Klagenfurt am Wörthersee is the only Austrian city that is part of the EU Cities Mission with the goal of climate neutrality by 2030. As one of 10 pioneering Austrian cities, it is playing a leading role on the path to climate neutrality: One of the key pillars is the renovation of existing buildings in the city (such as those in the Dag Hammarskjöld settlement) and the development of climate-neutral districts and neighborhoods.

The decisive factor in the WLCS (Whole Life Carbon Assessment) of a building is primarily the emissions that occur during its construction (embodied carbon), i.e., immediately before the building is put into operation (operational carbon).

Whether an existing residential neighborhood is demolished and new buildings are constructed in its place or whether the existing residential neighborhood is renovated makes a very big difference in terms of the CO₂e emissions emitted directly during construction.

Project contents and objectives

The Smart Dag project developed decision-making criteria that enable an objective assessment of whether, calculated over the life cycle and taking into account ecological, economic, and social factors, renovation or demolition/new construction ("reconstructing") is more sustainable and therefore more sensible from an economic, ecological, and social perspective. These decisionmaking parameters can subsequently be applied to other projects in Klagenfurt and other Austrian cities and municipalities.

Scientific monitoring also identified and highlighted obstacles and systemic areas of tension that arose. This serves as a basis for adapting the framework conditions.

Methodical procedure

The Smart Dag exploratory project involved a comprehensive and extensive survey of the existing buildings, energy, green and open spaces, and social fabric with the aim of gaining insights into the existing situation and thus establishing the best possible basis and objectives for the architectural competition.

A methodology for decision-making in renovation projects was developed. First and foremost, the survey and assessment carried out for the first time by "Quartier & Wir" should be mentioned, which shows how essential a high-quality preliminary survey ("Phase 0") is for all further phases of a project.

In addition to a mobility concept, an energy concept, and a green and open space concept, special attention was paid to the treatment and integration of residents in social housing with a diverse tenant structure—this also resulted in a social space concept.

Furthermore, innovative KPIs (key performance indicators) have been developed that can now be used to objectively assess the sustainability of projects. The research project examined and compared three possible variants: demolition/new construction ("reconstructing"), partial demolition and excessive redensification, and renovation and appropriate redensification.

The tender documents for an architectural competition were supplemented with specially developed sustainability criteria that are objectively measurable and verifiable and can be generally applied to other projects.

Results and conclusions

Contrary to previous claims, the renovation of the Dag Hammarskjöld residental area is demonstrably possible, as this option positively fulfills all KPIs—ecological, social, and economic.

The desired end result of the exploratory phase, namely to develop a project for submission to the housing s0ubsidy authority of Carinthia, could not be achieved due to delays in the project caused by external obstacles.

This is an important indication that large-scale renovation projects in particular cannot be separated from conventional operational logic and realpolitik systems.

It was also noted that the adjustment of framework conditions – subsidies and loan terms – currently disadvantages renovation and therefore urgently needs to be adjusted.

The structural engineering specifications were less of an obstacle in this case. However, it was important to clarify the situation with the local building authority at an early stage, which classified the construction work in the existing building as feasible by applying the OIB guidelines (Austrian Institute of Construction Engineering) and thus the renovation.

Outlook

Negotiations between Klagenfurt Wohnen (the city's own municipal company responsible for the management, maintenance, and provision of municipal housing) and a co-operative housing association regarding a building lease agreement are still ongoing.

One milestone is that the KPIs from the research project are included in the preliminary review catalog and other sustainability criteria are included in the assessment of the architectural competition, which is part of the building lease agreement in these negotiations.

In addition, based on the scientific results of this research project, the political advisor responsible for the housing subsidy authority of Carinthia is still sticking to the renovation of the Dag Hammarskjöld residental area. The positive economic effects of a renovation promote the common good and thus clearly outweigh individual interests that push for conventional demolition/new construction ("reconstructing").

In the KrAIsbau leading project, the Dag Hammarskjöld housing estate is the only multi-story residential building to be presented in the "affordable housing" segment. With the appropriate commitment from the owner, the estate can thus represent a significant segment of the Austrian building stock in this leading project.

Since Klagenfurt Wohnen considers urgent social support to be necessary during the change process, a service contract will be signed with Diakonie de La Tour starting in 2026 for further social work support and advice on inclusive neighborhood development through psychosocial support and citizen-oriented communication in the context of developments in the Dag Hammarskjöld residental area. This includes, among other things, the following points:

Project management and management of citizen participation in cooperation with Klagenfurt Wohnen, ongoing low-threshold outreach social work, workshop moderation and design, on-site social work in the sense of clarification through individual or group case assistance, relief and de-escalation, as well as support and mediation.

Project management

Municipality of the provincial Capital City Klagenfurt on lake Woerthersee, department of climate and environmental protection

Project or cooperation partners

• FH Kärnten Villach, Studiengang Architektur
• Renowave.at
• IPAK GmbH
• Diakonie de la Tour
• Klagenfurt Wohnen

Magistrat der Landeshauptstadt Klagenfurt am Wörthersee
Abteilung Klima- und Umweltschutz
Bahnhofstraße 35
A-9020 Klagenfurt am Wörthersee
Tel.: +43 (463) 537 4886
E-Mail: wolfgang.hafner@klagenfurt.at
Webseite: www.klagenfurt.at/stadtservice/klima-umwelt/laufende-projekte