Mariahilferstrasse 182


Vienna, Austria


Trimmel Wall Architekten ZT GmbH
Johann-Hörbiger-Gasse 30, 1230 Vienna - Mauer


Contact Details

Susanne Kuchar
e7 energy innovation & engineering
+43 1 907 80 26 - 67

Other Information

Modernization of a Gründerzeit building with the use of an aerogel insulating plaster
Energy performance
27,7 kWh/m2.y

Climate Zone Cfb

Altitude 199 m a.s.l.

HDD 3490


Protection level Not listed

Conservation Area:

Level of Protection:

Building age 1850-1899

Year of last renovation:

Building use Residential (urban)

Secondary use:

Building occupancy:
Permanently occupied

Number of occupants/users:

Building area Net floor area [m²]: 3072,0

Building typology:
Semidetached house

Number of floors:

Basement yes/no:

Number of heated floors:

Gross floor area [m²]:

Thermal envelope area [m²]:

Volume [m³]:

NFA calculation method:
NGF (de)

Construction type
Brick masonry wall

External finish:

Internal finish:
Plastered (on hard)

Roof type:
Pitched roof





The building consists of 29 residential units, of which 9 apartments and around 760 m² of living space are attributable to the newly developed two-storey attic floor. In the ground floor zone, around 270 m² of commercially used local space as well as a garage with 7 parking spaces with an e-charging station were converted, for which the inner courtyard on the ground floor was overbuilt. In addition to the restored façade, the exterior of the new attic storey is initially noticeable. But the renovation is also accompanied by a comprehensive improvement that in not obvious at first glance. The existing staircase was in danger of collapse, a circumstance that the architectural team used to reorganize the access situation and a large part of the ground floor, thereby gaining space for, among other things, a bicycle storage room and a garage. An invitingly designed entrance first draws the eye to a leafy atrium. An elevator and a light-flooded staircase were newly built in the courtyard. The partial demolition of the side wings and the raising of the yard level improved the light situation in the courtyard and radiate positive to the immediate neighborhood. The building recieved two major awards: the 1st prize of the 33rd Vienna Urban Renewal Prize by the National Guild Construction Vienna, and the State Prize for Architecture and Sustainability 2019 by the Federal Ministry for Sustainability and Tourism. The implementation of this project was carried out within the framework of the R&D programme "City of Tomorrow". The innovative renovation measures as well as the accompanying research and documentation were funded by the Austrian Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology and the City of Vienna.
Urban context
The existing property is located in the 15th district of the city of Vienna on the corner of outer Mariahilfer Straße and Denglergasse. The area is a mixed zone of habitation and commerce along a main traffic axis within the district.


The old structure as well as the facade were worthy of preservation.
Heritage Value Assesment
The building dates back to the Gründerzeit and is typical for a building from this period in one of the districts surrounding the center of Vienna. For well over a hundred years, the Wilhelminian structure that characterises the face and body of the Austrian capital has proven itself to be adaptable and robust in the changing times. But it is also a popular investment area where the logic of the market reigns. When looking at the images that went through the media after the devastating gas explosion in April 2014, many people probably assumed that a piece of the historical cityscape is in danger of being lost here. But things turned out differently, and four years later the building shone in new splendor. The will of the owners to rebuild the apartment building was supported by the City of Vienna. Embedded in an ongoing block renovation offensive in the Rudolfsheim-Fünfhauser district of Rustendorf, the reconstruction was also the subject of a research project on the thermal optimisation of richly structured Wilhelminian style house facades.

State of repair

Conditions of the envelope
In April 2014, the building was badly damaged as a result of a gas explosion in an apartment in the wing on Mariahilferstraße on the 2nd and 3rd floors.
Description of pre-intervention building services
The heat generation for warm water and space heating took place over a gas boiler. Electricity and cold water were recieved from the public grid.

Aim of retrofit

Renovation + Extension
In the building, the application of airgel high-performance insulation plaster was implemented using the example of the renovation of a Gründerzeit building. The airgel high-performance insulation rendering system provides a new alternative for the field of old building renovation with well-preserved facades. The ultimate goal was the demonstration of the technical feasibility and practicality of such remediation solutions. Another project objective was the metrological monitoring of the project for the evaluation of the total renovation and the effect of the plaster . For this purpose, an energy consumption and comfort monitoring was implemented.
Was there any change of use?
A garage for cars and bicicles was added to the building.
Lessons learned
The visible result is the successful refurbishment of a historic building where it has been possible to restore the external appearance and achieve a visually unrecognizable transition between old building and reconstruction. The high structural and design requirements were fully met and high visibility of the project achieved (mainly by winning the 33rd Vienna Urban Renewal Award of the Guild Construction). At the same time, the high demands of an energy-efficient building stock could be fulfilled, even though the metrologically determined heat transfer coefficient does not fully correspond to the calculated values. The supplementary evaluation by means of long-term monitoring takes place after the first or second year of operation.
Stakeholders Involvement
Public sector
Federal Ministry for Transport, Innovation and Technolog (BMVIT)
Radetzkystraße 2, 1030 Vienna
Private Sector
Brun Immobilienverwaltung und – Vermittlung
Grimmgasse 31, 1150 Vienna
Research Development
Technical University Vienna, Institute of Construction, Structural Dynamics and Building Technology
Karlsplatz 13/208, 1040 Vienna
Trimmel Wall Architekten ZT GmbH
Johann-Hörbiger-Gasse 30, 1230 Vienna - Mauer
Energy Consultant
e7 energy innovation & engineering
Walcherstraße 11/43, 1020 Vienna
Structural Engineer
Dr. Karlheinz Hollinsky & Partner ZT Ges.m.b.H
Münichreiterstraße 25, 1130 Vienna
Schöberl & Pöll GmbH Bauphysik und Forschung
Lassallestraße 2, 1020 Vienna
Tools used
Was the renovation process done following a specific methodology? An energy consumption and comfort monitoring started in February 2018 and is evaluated over a period of 2 years.
Energy calculation Energieausweis calculation and metrological investigation
Hygrothermal assessment Comfort monitoring with heat meters and sub-flow meters to show the energy flows in the building. Temperature and humidity sensors in the ventilation system and for detecting the outside climate.


External Walls

Exterior wall

Exterior wall

Along Denglergasse, on an area of around 205 m², Austria's largest airgel façade was built. Until now only tested on inner walls and smooth walls, this offered the chance to use the aggregate, which has extraordinarily good thermal insulation properties, on an articulated façade. With only five centimeters of the machine applied airgel plaster, the effect of a 15 centimeter thick, conventional insulation board can be achieved - an excellent environmental and aesthetic option. On the Mariahilfer Straße, the façade was much more damaged. Therefore, the newly constructed outer wall was moved a bit to the inside of the building to be able to attach 20 cm of hemp insulation. The decorative parts of the façade were made of prefabricated foam glass parts. Generally, PVC-free building materials were used.

Destroyed facade decoration elements were refilled in cooperation with a restorer made of foam glass, because a restoration from the original material would not have been economically justifiable.

U-value (pre-intervention) [W/m2K]: 1,13 W/m²K U-value (post-intervention) [W/m2K]: 0,301 W/m²K
More Details
Original wall build-up
Render :
20 mm
Brick :
620 mm
Plaster :
10 mm
Retrofitted wall build-up
Other - Airgel insulation render:
Brick :
620 mm
Plaster :
10 mm

Other interventions





A two-storey loft conversion with seven additional maisonettes and around 760 m² of living space was realized.

Special importance was attached to a high energy-technical standard, the loft conversion meets the passive house standard.

U-value (post-intervention) [W/m2K] 0,303
More Details
Original roof build-up
Retrofitted roof build-up

Textile Window awnings: Aubergine-colored textile webs of roll-out sunscreen were attached to the windows. They bring accents to the cityscape and increase living comfort on hot days clearly.

Old cityscapes, prove that window-awnings, which are more familiar from southern cities, used to be common in Vienna. This encouraged the implementation of the new textile sunscreens.


Air exchange rate: n50 = 1,0 1/h

Airtightness (post-intervention) [ach@50Pa] 1





There was a changeover from a decentralised gas heating system with thermae to a centralised system in which a solar thermal system is integrated. Unfortunately, it was not possible to connect to the district heating network, but everything is prepared to change the energy source as soon as the district heating pipeline passes by the house in the foreseeable future.

The new heating system did not interfere with the conservation compatibility.

More Details
New primary heating system
New system type Boiler
Fuel Gas
Distribuition system Radiating floor, ventilation system and buffer tank for water heating
Nominal power 150 kW kW

Controlled ventilation of the residential units is provided by a central compact ventilation unit from the Systemair TOPVEX SC08 HW series. The air volume in the residential units is controlled by means of volume flow controllers. The unit is equipped with a recuperative heat recovery unit with bypass. The design volume flow rate is around 3,000 m³/h, the specific fan output is specified according to the data sheet as 0.456 Wh/m³ at nominal volume flow.

The new ventilation system did not interfere with the conservation compatibility.

More Details
Original roof build-up New ventilation system
Type ventilation system Centralized controlled aeration and ventilation
Type flow regime Overflow
Heat recovery Yes
Humitidy recovery No
Nominal power 10 kW kW
Electric power kW
Control system Air volume control in the residential units by means of volume flow controllers




A solar thermal system, which is located on the roof of the building, supports the hot water supply.

The new solar thermal system did not interfere with the conservation compatibility.

More Details
SolarThermal System
Type Flat collector
Collector area 30,0 m²
Elevation angle 45,0
Azimuth -5,0
Heating_contribuition 0,0 kWh
Cooling contribuition 0,0 kWh

Energy Efficiency

Energy Performance
Energy performance certificate: There are 3 energy certificates (Austrian "Energieausweis") for different parts of the building after the renovation: the retail area in the ground floor, the attic floor, and the other floors.
Energy Use
Primary Energy 92,3 kWh/m2.y
Consumption_estimation_After: 27,7 kWh/m2.y

Primary Energy
Consumption_estimation_Calculation_method: OIB 2015
Consumption_estimation_After: 92,3 kWh/m2.y
Measured Parameters
Internal Climate
Type_of_monitoring: Continuous
Description: The three parameters room temperature and humidity, summer overheating, and CO2 concentration were continuoulsy measured for two years.

External Climate
Type_of_monitoring: Continuous
Description: The average daily outside temperature at the site and the resulting heating degree days 20/12 were measured continuously over a period of two years (2018, 2019). The site-specific heating degree days (20/12) add up to 2,229 HGT in the second year of measurement. In the first year of measurement 2,471 HGT were determined. In the energy performance certificate, these are set at 3,490 HGT. This results in a difference of 242 heating degree days compared to the first year of measurement (-10 %), or 1,171 heating degree days to the calculation basis of the energy certificate. In the second year of measurement, the outdoor temperature records only show isolated daily mean temperatures below freezing point. A cold period as in the first measurement year before was not recorded. In the second measurement year, a long period with very high outside temperatures and peaks above 30°C is recorded, but below the level of the first measurement year.

Internal Climate


The room air temperature during the heating period is above 20 °C in all residential units, in two residential units mostly above 22 °C. There is a strong correlation between outside and inside temperature. Especially the one-room apartment shows strong overheating tendencies. The lowest indoor temperatures in summer are recorded in the apartment, which has, among other things, higher external shading from other buildings.

Indoor Air Quality

Humidity: With regard to the room air humidity, it can be seen that in two reference apartments the winter room air humidity decreases to about 20 % and can therefore already be classified as dry. The maximum room air humidity, on the other hand, is almost below 60 %, so there is no risk of condensation damage. CO2 concentration: The CO2 concentration was measured in three reference apartments in the bedroom and in one apartment in the kitchen. All residential units in the building are connected to the central comfort ventilation system. The level of CO2 concentration is at a very low level and does not exceed a limit value of 1,000 ppm. It can be concluded that the air volumes for these residential units are sufficient or slightly oversized.


Investment Costs
Total investment costs
7,000,000 € (total)
Amount includes: The total costs for the production of the finished facade surface were calculated with 200.000 Euro settled. The costs include all necessary activities from preparation of the existing facade (knocking off old plaster, pre-spray work, etc.), the application of the aerogel plaster incl. substrate preparation and finishing plaster as well as the formation the traction and decorative elements and the cornices. This results in specific costs of around 800 euros per m² of facade surface. The aerogel insulation plaster is just over 400 Euro per m² with an executed layer thickness of 5.5 - 6 cm and thus makes 50 % of the total production costs of the façade. The costs are thus around one third above that of a standard thermal insulation plaster.
Running Costs
Lifecycle cost


Greenhouse Gas Emissions
Methodology_used: OIB 2015
emissions_at_use_stage_after_intervention: 14,32 per m2
Transport and Mobility

7 car parking spaces with e-charging station with separate billing were established.

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