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St. Leonhard Primary School and Kindergarten: Municipal renovation in Austria

Wyróżniony Przypadek January 2016
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To accommodate the growing number of students attending the St. Leonard School built in 1964, the school was expanded and modernized. In 2010, the site has also incorporated a kindergarten, an after-school club and a public library.


The biggest challenge of this project was renovating the building to passive house standards.  Initial tasks of minimizing the number of thermal bridges, adding interior insulation and removing any heat loss were performed to further improve the energy values. The main solution was based on the use of prefabricated timber facade elements as well as the use of renewable energy sources for heating, domestic hot water and electricity.


Another big challenge was the completion of a 5 month construction deadline which was rather tight due to all the technical challenges of the existing poor static and structural conditions. This achievement, as well as the reduction of the energy cost being 10 times less than the previous one (approximately 17.000€/year), confronts the global perception that renovating for high-energy efficiency is slow and expensive.



High-energy efficiency measures for renovation

  • Passive House standard
  • biomass (pellets) and PV
  • centralized mechanical ventilation system with heat recovery
  • focus on improvement of indoor air quality




St. Leonhard bei Siebenbrünn 11, 9587 Arnoldstein, Austria


Project team


Project management and client: Umwelt und Innovation Arnoldstein GmbH (UIAG)

Main contractor and design: ARCH+MORE ZT GmbH - DI Gerhard Kopeinig

Structural engineering: DI Klaus Gelbmann

Building owner: Municipality Arnoldstein Municipality

Prefabricated timber façade elements: Weissenseer Holz-System-Bau GmbH


Time schedule


Built: 1964

New auxiliary building (gymnasium): 2005

Main building renovation (primary school and new kindergarten): 2010 - completed in a 5 month period


Surface areas / building use


The plot area is 7.700 m2 and contains two buildings: main building and auxiliary building. The building renovation was only performed in the main building. This 2-storey building with a semi-basement was divided into 3 parts: primary school, kindergarten and after-school club. Therefore, a functional reorganization of the space concept was implemented according to each floor level:

-Semi-basement: after-school club room, kitchen, WC and other auxiliary rooms (replacing the old gymnasium dated from 1964)

-Ground floor:  library (replacing the old caretaker´s apartment) and a Kindergarten (new single-storey building extension).

-First floor: no changes, this space is occupied by the primary school classrooms.



More details:



Main building

Auxiliary building

Total constructed area

Total renovated area

Primary school


After-school club


Usable Floor Area (m2)








Renovation costs


The total project costs are listed in the next table:



Main building

Auxiliary building


Primary school


After-school club


Renovation costs (€)




Not applicable


Renovation costs (€/m2)




Not applicable



The Carinthian school building funds financed 75% of the retrofit and the Austrian Research Promotion Agency (Forschungs-Förderungs-Gesellschaft) financed 25%


Envelope performance

Prefabricated timber facade elements were used, which were produced off-site about 2 weeks before the on-site installation. No temporary move was required. The roof of the building was also insulated, and both roof and outside wall achieve a u-value lower than 0,10 W/m²K after the renovation. New triple glazed windows with total u-value of lower than 0,8 W/m²K were integrated into the prefabricated facade elements.


More details:


Exterior walls: 0.090 W/m2K

Floor: 0,134 W/m2K

Roof: 0,065 W/m2K

Windows: 0,693 W/m2K

Air tightness: 0,40m3/hm2


Energy consumption


The energy consumption was previously calculated through the official energy certification software:

-Primary energy consumption (before renovation): 121,4 kWh/m2.year

-Primary energy consumption (after renovation): 7,8 kWh/m2.year (95% energy saving estimated)

-Primary energy consumption (heating and cooling only): 5,6 kWh/m2.year


After one year of building use, the final energy consumptions were obtained in order to estimate the real energy savings (result: 81% of energy saving):



Main building

Auxiliary building


Primary school


After-school club


Final energy consumption before renovation (Kwh/year)






Final energy consumption after renovation (Kwh/year)




Not improved


Energy saving (%)




Not improved


Saved energy costs (€/year)




Not improved




Energy systems


Ventilation system for indoor environment quality


A central mechanical ventilation system with 80% heat and moisture recovery was installed. The ventilation system is controlled based on the CO2 concentration in the classrooms. The ambient air is preheated by a separate brine system before entering the heat exchanger. Before the preheated air gets to the classrooms, the wood pellet furnace heats the supply air to at least 24°C (if necessary) to guarantee high thermal comfort in the classrooms.


Heating and cooling system based on wood pellets and complemented by PV


This type of technology estimates a 90% energy cost reduction (due to the replacement of an oil boiler with a biomass boiler), gives 85% of renewable energy coverage of the final energy consumption and a calculated CO2 reduction in operation around 39 kg/m2.year.

The PV installation is located on the gymnasium roof with 5kWp of installed power.


Awards and recognition

Awarded renovation project in the 2011 ISOVER Energy Efficiency Best Awards, with the title reference “Five months to reduce energy consumption” (


Additional Links

Video of the renovation in German:

Leaflet in German:

Project description and photo gallery:

Video at ORF news:

Technical presentation:

Lessons learnt

In general, the feedback from the renovation of the school building was very positive from all involved, especially from the school owner and the occupants (teachers and pupils). The only potential for optimisation is the introduction of the mechanical ventilation system in the school on a daily usage. Although instructions have been imparted and documentation has been handed over, the school occupants had difficulties with the use of the mechanical ventilation in the beginning.

Award labels

Available link languages


The project received the ISOVER Energy Efficiency Award in 2011

Funding description

Carinthian school building funds financed 75 % of the retrofit and the Austrian Research Promotion Agency financed 25%