Gründerzeit with future - demonstration project 2: ROOFJET Wißgrillgasse - sustainable solution for improving the thermal-energetic performance of a typical historical building in Vienna

The main aim of the project ROOFJET Wißgrillgasse is a building refurbishment by a factor of 8 which demonstrates that even historical buildings can be refurbished to lowest energy standard.
This demonstration project shows a holistic and sustainable refurbishment concept for a special type of buildings with innovative technical and organizational solutions.

Short Description

This project is a sub project of the flagship project "Gründerzeit with future: Innovative Modernisation of Wilhelminian style "Gründerzeit" Buildings"




Starting point / motivation

Wilhelminian style or "Gründerzeit" buildings with typically decorated façades represent a considerable part of the total building and housing stock in Austria. These buildings were constructed between 1850 and 1918 and are in poor thermo-technical conditions. Hence, possible savings are huge with regard to a CO2-neutral building stock. However, with application of usual refurbishment measures (replacement of windows) the energetic performance may be improved slightly. This demonstration project Wißgrillgasse shows how innovative refurbishment of Wilhelminian style buildings can overcome technical, economical, social and legal barriers and achieve a great performance. The demonstration project is part of the flagship project "Gründerzeit mit Zukunft".

Contents and goals

An integral modernization of the building was put forward by applying innovative technical and organizational solutions, which assure a modern living standard with high comfort. The building was refurbished energetically and a high efficient attic was developed. Goal of the project was a comprehensive and sustainable system solution, which allows a broad reproduction to further Wilhelminian style buildings.

Methods of treatment

Optimization of thermal quality of the building shell was keen. Therefore, insulation of all exterior building elements were risen up to a very high level in order to reduce energy demand for thermal heat. Due to usage of high efficient insulation materials losses of surface area could be reduced. Special attention was given to insulation of the fire-proof wall, because this wall accounts for 32% of all exterior walls. In order to secure interests of the neighborhood special neighborhood arrangements were made. This was especially important to enable insulation beyond property lines. Exclusively heat insulation triple glazing was used. Thus, transmission heat losses could be kept little.

Additionally a central comfort ventilation system and a local incoming and outgoing ventilation system with thermal heat recovery was installed in the top floor. Thus heat losses due to ventilation could be reduced significantly. High noise pollution due to the railway junction was a further reason to install such ventilation systems.

Given that Wißgrillgasse is not covered by the supply of district heating the developer decided in favor of a central biomass heating system, which ensures a resource efficient allocation of energy for thermal heat and hot water. Drainage of the cellar was important to maintain the building substance, which proved to be very extensive, but was keen in order to guarantee a dry storage of wood pellets. Additionally 30 m² solar thermal collectors were integrated into the façade and cover a part of the required energy demand for thermal heat and hot water.

It has to be highlighted that the development of an attractive living space in the top floor is keen to realize such projects. This project accomplished a development of additional 800 m² useable surface by restructuring the existing building and development of a two-storied top floor in nearly zero energy standard.


Initially the heating demand was 186 kWh/m²a. Due to the application of above mentioned measures the heating demand could be reduced to 28 kWh/m²a, what corresponds to a refurbishment with factor 7 and hence a nearly zero energy building. This demonstrates far better performance compared with conventional new buildings. The building convinces with its high thermal quality and usage of renewable energies but also with its high comfort of living and pleasant architecture. Furthermore success may be proven by the residents, who are highly satisfied with the building and and experts show strong interests in viewings.

The high thermal-energetical quality of this demonstration project with innovative technical and organizational solutions shows fair possibilities how the refurbishment of Wilhelminian style buildings could make an important contribution to a CO2-neutral building sector.

Prospects / Suggestions for future research

In order to draw serious conclusions about the factual performance of the building the project will be subject to a technical energy demand and comfort monitoring within the framework of the flagship project “Gründerzeit mit Zukunft” for a period of two years. Beside energy demands satisfaction of users and economical efficiency will be evaluated.

The experiences gained during the construction and accompanying monitoring phase will be incorporated immediately in further development projects of the builder Ulreich Bauträger GmbH and the Gassner & Partner Baumanagement GmbH. In addition, to the in-house usage of gained experiences and use for further demonstration projects within the knowledge about refurbishment of Wilhelminian style buildings will be disseminated by excursions, publications in journals and presentations.  

Project Partners

Project management

Mag. Hans Jörg Ulreich
Ulreich Bauträger GmbH, Wien

Project or cooperation partner

  • Ing. Robert Gassner
    Gassner und Partner GmbH, Wien

Contact Address

Mag. Hans Jörg Ulreich
Ulreich Bauträger GmbH
Obere Amtshausgasse 20-24, 1050 Wien
Tel.: +43 (1) 7866110
Fax: +43 (1) 7866110-10