Passive houses on Mühlweg, Vienna (AT)
New building,
Affordable housing
Client: Bauträger Austria Immobilien GmbH
Location: A-1210 Vienna, Mühlweg 74
Architecture: Dietrich Untertrifaller
Competition: 2004, 1. prize
Construction: 2005 – 2006
Area: 13,350 m²
Programme: 4 buildings with 70 flats in passive house standard
Photos: Dietrich Untertrifaller, Bruno Klomfar
Team
Andreas Hammer, Jana Sack, Thomas Weber (Project management)
Text: Gerlinde Jüttner
Partners
Statics: JR Consult, Graz
Building services: Ökoplan, Vienna
Building physics: IBO, Vienna
Landscape: Barbara Bacher, Linz
Timber construction: KLH Massivholz, Katsch
Awards
- Energy Globe Vienna, Award
First large-scale passive houses in timber
Already 20 years ago, we built a multi-award-winning passive house residential complex in the north-west of Vienna, in front of the Bisamberg vineyards. The residential buildings represent a new, innovative type of building, as they were the first large-volume passive houses to be realised in mixed timber construction.
The complex with 70 subsidised rental flats is arranged around a central green area and consists of four compact, free-standing buildings: three with 18 residential units each and one with 16. The ground floor of the latter houses a shared flat and a starter flat for the SOS Children's Village. The three upper floors and the top floor were constructed from prefabricated timber elements, while the ground floor and staircase are made of reinforced concrete.
The façade was prefabricated element by element in the factory. Windows, insulation and base plaster had already been installed and applied. This had a particularly positive effect on the quality of the sealing measures, as work could be carried out more precisely and carefully in the factory than on the construction site.
On each floor of the compact, four-storey apartment blocks, four flats are arranged around the internal stairwell. The recessed attic storey is shared by two flats. All flats have private open spaces such as terraces, loggias or balconies. While three houses are arranged in parallel, the fourth is rotated by 90 degrees to open up the centre zone with playground to the south.
Rainproof after five days of construction
The fact that wood could once again be used as a building material in multi-storey residential construction in Vienna was made possible by an amendment to the Vienna Building Code implemented in 2001. The Mühlweg timber and mixed timber construction was one of the first projects to be realised since then.
In contrast to a bar structure, we used timber in these buildings in the form of solid panels and panes of cross-laminated timber, which form the load-bearing structure around the staircase, which is raised in reinforced concrete. After just five days of construction, the shell was rainproof.
The façade was prefabricated element by element in the factory. Windows, insulation and base plaster had already been installed and applied. This had a particularly positive effect on the quality of the sealing measures, as it was possible to work more precisely and carefully in the factory than on the construction site.
The finishing plaster was applied to the shell after assembly, so that the building has a solid appearance and only the attached loggias and the attic storey are visibly made of wood.
The building's heating requirement is only around 15 kWh/m²a, in line with passive house requirements. This was achieved through a thermal bridge-free construction, triple-pane thermal insulation glazing with highly insulating frames and a ventilation system with heat recovery. Solar collectors are used to support water heating. The wood fibre insulation was installed in the prefabricated elements at the factory and combined with vacuum insulation in some places. This means that even smaller cross-sections guarantee an insulating effect suitable for passive houses.
