The very first reconstruction in Austria of a one-unit house to passive house standard (Model project in Pettenbach/Upper Austria)

The main objective is the unprecedented reconstruction of older one-unit buildings to the standards of passive houses. The reconstruction estates are of the numerous older one-unit houses in Austria. The reconstruction will considerably enhance the convenience of living quarters in the old houses.

Content Description




The exemplary implementation of the passive-house standard and comfort in the rehabilitation of already existing single-family homes as demonstrated in the house of the Schwarz family at Pettenbach, Upper Austria is unique for Austria. Apart from the dramatic reduction of energy consumption amounting to around 95% and of CO2 emissions for room heat by 100%, this show-case project within the framework of the research programme line called "House of the future" conducted by the Austrian Federal Ministry of Transport, Innovation and Technology ("BMVIT") focussed primarily on the innovative modernisation and rehabilitation concept based on a high degree of prefabricated hook-in timber wall elements.

As for the floor, the high insulation standard could be reached by using vacuum insulation although the floor height was limited. The thermal bridges of the existing rising brickwalls were compensated by a circumferential umbrella-shaped insulation. With this, the heating energy requirement of 27,100 kWh/a of liquid gas were reduced to only 3,170 kWh/a power generated from solar energy, even though the useful floor space was doubled from 97 m² to 217 m²!

The optimized ventilation system using a highly efficient compact unit ensures permanent supply of fresh air throughout the building and covers the required residual heat and hot water demand. The 2.4 kWp photovoltaic panels integrated into the façade cover the entire residual heat demand.

The use of a maximum quantity of renewable resources and the upgrading of the old building instead of tearing it down and building a new house also cut the consumption of non-renewable raw materials and of grey energy by 80%.

Compared with conventional rehabilitation methods, the consistent conversion of the building to fulfil the passive-house standard has caused additional costs of 16%, the use of ecological measures additional costs of 11%. Due to the dramatically lowered energy costs, the anticipated rise of heating expenses and eligibility to obtain the highest public subsidy scheme, consistent rehabilitation will pay off for the building owners within a few years. Residents will certainly no longer have to worry about soaring energy prices!


The thermally sustainable rehabilitation of old buildings is the most important contribution by far to achieve effective reduction of CO2 emissions within the Kyoto framework, while at the same time offering the opportunity of providing buildings in need of rehabilitation with a high level of energy efficiency and user comfort from the very beginning. Compared with conventional rehabilitation, it is in particular the comfortable ventilation and air extraction system including heat recovery that guarantees a permanent supply of fresh air in all rooms and comfortable living quality like in a new building.

"Living comfort, energy saving and climate protection are no contradiction, but the best way to secure the future. The passive house offers the best prerequisites of providing a sound and healthy climate both in the construction of new and rehabilitation of old buildings." Sustainable efforts to save the climate call for dedicated projects and committed people.


Very promising cost/benefit effects were achieved for the rehabilitated and the new part of the building:

  • High occupational quality: Good fresh air quality in all rooms, improved daylight situation, considerably improved thermal comfort. High degree of prefabrication and short installation time on the construction site.
  • Very low energy requirement: Heating energy and primary energy demand according to passive-house limit values 95% lower than in the existing building and around 75% lower than with conventional rehabilitation.
  • Enhanced building quality: High building value due to sustainable, long-term rehabilitation measures, low life-cycle costs.
  • Role-model effect: First rehabilitation of a single-family house according to the passive-house standard, future-oriented concept in all fields of energy efficiency and state-of-the art residential housing

Innovative aspects

The encasement of the ground floor is the basis of the innovative rehabilitation concept. Adapted to the existing building, the suspension points were set and measured, and the hook-in parts were pre-installed on the wall elements as provided for by the 3D-CAD planning.

The elements including the façade and the windows without any further attachment were installed smoothly on the spot during the first day. This is how the timber construction can make full use of its benefits even in the rehabilitation of old buildings. The insulation material used was cellulose, which levels out the irregularities of the existing building, leaving no joints at all.

This pilot project has paved the ground for a wide-range application of the revolutionary wooden construction system in old buildings.

Converting schools during the school year, office buildings during working hours and residential buildings with inhabitants living inside and without impairing the users too long. Within a few days, the buildings will receive their completely new and highly heat-insulating envelope. A future-oriented market segment for timber construction!

Thermal bridges in the rising brickwall were reduced by an extensive, thick umbrella-type insulation in the ground. While making up for these gaps certainly is key to successful rehabilitation of existing buildings to passive-house standard, this is often neglected, "because they seem to be invisibly buried in the ground".

Sustainability / efficiency

Rehabilitation allowed maintaining the existing building substance and using new construction materials by sparing resources. Despite of the double volume of construction elements, the consumption of non-renewable raw materials was reduced by some 80 %. Equally positive is the life-cycle analysis of the "grey energy". Supreme efficiency and sustainability of the pilot project concerning energy and CO2 emissions.

Table: Comparison before and after the refurbishment

  before after
Useful floor space [m²] 97 217
Heating energy requirement [kWh/a] 27.100 3.170
Energy source Liquid gas 2,4 kWp
PV plant
Heating energy requirement
[kWh/m²a] according to PHPP
280 14,6
  - 95%
CO2 emissions   - 93%
Airtightness n50 5,1 h-1 0,5 h-1

Additional costs pay off from the very first day!

Compared with conventional rehabilitation measures, the consistent conversion into a passive house has generated additional costs of 16%, the use of ecological measures additional costs of 11%, but at the same time, the building owners obtain the maximum government subsidies and grants. The remaining higher bank loan is fully covered by dramatically reduced energy expenses. Additionally, bank interests are lower than the anticipated increase in heating costs; this is why consistent rehabilitation of old buildings pays off in any case.

  • Construction costs: 1,456.- €/m²
  • Construction period: November 2004 to June 2005

Project Partners

Project leader

Ing. Günter Lang, LANG consulting

Project partners

  • DI Bernd Krauß, planungsteam E-plus
  • DI H.C. Obermayr, Obermayr Holzkonstruktionen GmbH
  • Roland Wimmer, Schloßgangl GmbH & Co KG
  • Arch. DI Heinz Plöderl, PAUAT Architekten
  • TB Panic, Emanuel Panic
  • Gabriele & Ing. Werner Schwarz, Bauherrn


Ing. Günter Lang
Linzerstraße 280/6, A-1140 Wien
Tel.: +43 (650) 9002040
Fax: +43 (1) 9111929