Fennerstrasse/ Oswald-Redlichstrasse

Demonstration site profile

Name and Address

Name of the demo site: NHT IN28

Address of the demo site: Fennerstraße & Oswald-Redlich-Straße/ IN 28, 6020 Innsbruck, Austria


City map highlighting the surface occupied by the demo site (source: http://city-map.innsbruck.gv.at)  


NHT already finished the innovative overall building renovation, consisting of the process innovation (e.g. tenants involvement process, implementation of ventilation system etc.) and the technical components of the refurbishment (e.g. insulation, PV on the rooftop, etc.). Issues such as apartment entrance doors and a new locking system have been completed. NHT is fully satisfied with the completed refurbishment of IN 28. NHT convinced the tenants of the meaningfulness and the positive aspects of the ventilation system during the refurbishment of IN 28.

Ownership: Neue Heimat Tirol (NHT)

Gross conditioned floor area (EPC): 7.359 m²

Treated floor area (PHPP): 
5.919 m²

Number of dwellings: 

Heating demand (EPC)



Heating demand (PHPP)



Overall savings after completion of ventilation & heating system: >80%

Description before refurbishment

All objects are patched via 1 long complex of buildings and 1 small one.

IN28 is typical building block constructed in the second half of the 20th century with related challenges in regards to insulation, electric cables, low performing windows, uninsulated roofs and cellars, etc

Technical system
: Decentralised heating system

Energy performance certificate: 
Category C

Refurbishment concept


Thermal renovation of the walls, the ceiling, the roof and the windows with triple-glazing. The thermal bridges of the balconies were minimized through insulation of the floor of the balconies.

Energy solutions

  • The attics are insulated with a 30 cm layer of EPS
  • The facade is additionally insulated with 16 cm of EPS
  • Thermal insulation of inner yard (12cm Polyurethan)
  • Perimeter Insulation between 6 -14 cm
  • The walls & ceilings to the stairway and basement are equipped with 10 cm of Tektalan (mineral wool). New de-centralised gas boilers will also be partly installed.
  • A VAV-controlled central ventilation system is placed in the cold attic
  • DHW via electric de-central water heater
  • New LED in all public spaces

The PV system will be installed as a full feed system so that the generated energy will feed the public grid while the Austrian agency for green electricity compensates the missing power.

Replacement of windows to reach app. 70 % better thermal performance.

Performances targets

Target is to achieve a calculated energy consumption per m² of total used conditioned floor area of about 24 kWh/m²*a (EPC). In addition electricity savings between 30 – 40% should be achieved.

Financing model

The refurbishment is financed via a mix of reserves as well as local/ regional/ national/ EU funding and includes an increase of the monthly rent from 4.38 €/m²*month to 4.71 €/m²*month whilst reducing the average charge for operation, maintenance and other running costs from 1.25 €/m²*month down to 0.85 €/m²*month. 

Envelope details

Roof to wall insertion section (thermal bridge)

Insulation of the attic floor by using 20 cm EPS in addition to the existing 10cm.

Ground to wall section (thermal bridge)

Additional thermal insulation of the lowest storey ceiling of 17.5cm Tektalan

Wall to fenestration section (thermal bridge

  • Thermal insulation of façade (22cm EPS)
  • Thermal insulation of inner yard (12cm Polyurethan)
  • Perimeter Insulation between 6 -14 cm 
  • Replacing windows to reach app. 70 % better thermal performance 

Technical system

Mechanical ventilation3 centralised ventilation systems are implemented and connected to 31% of the building users. All other apartments will be upgraded on long-term.

Electric renewable integration

Nominal power of PV IN 28:               41,08 kWp

Mounting type:                                  Roof mounted parallel

Elevation:                                         574 m a.s.l.

Tilt:                                                  25°

Azimuth angle:                                  248 °/126°

Financial model:                                Feed-in-tariff


Nominal power of Fennerstraße:          27,82 kWp

PV array area:                                   178 m²

Module type:                                     Solarwatt Blue 60 P, 260 W

Inverter type:                                    1 x Fronius Symo 20.0-3-M

                                                        1 x Fronius Symo 8.2-3-M


Nominal power of Oswald-Redlich-Str.:          13,26 kWp

PV array area:                                    84,8 m²

Module type:                                      Solarwatt Blue 60 P, 260 W

Inverter type:                                     1 x Fronius Symo 12.5-3-M



Stakeholders involved

Contracting authority: NHT Neue Heimat Tirol

Project manager: Gerda Maria Embacher

Architect/Envelope Designer: Architekt Vogl-Fernheim

Technical system designer:
 Fa. Klimatherm, Zirl (HKSL),  Fa. Obwieser, Absam (ELO)

Construction company:
 Fa. Bodner

Windows supplier: 
Fa. Alutherm, Innsbruck

Safety supervisor
: Kopecky Karin

 Hutter und Söhne, Innsbruck

Energy consultant, scientific support
: University of Innsbruck and Passive House Institute – Department Innsbruck

Refurbishment costs

Total investment  of app. € 2,5 Mio.

Work Progress

The challenges in the course of the refurbishment of residential buildings are complex and multi-layered. Financial and social aspects and challenges need to be considered, because the tenant has to co-finance some parts of the renovation, which requires the implementation of persuasion and tenant engagement activities. Furthermore, legal challenges also have to be solved. The most intensive persuasion is to be done in the field of nearly zero energy house renovation and especially in cases where tenants are living in the flats during the time of ventilation system installations and other intrusive renovation activities.

Description after refurbishment

Architectonic concept

Renewable energy sources

Prognosis of the yearly yield: 43,755 kWh/a

End-Energy use (EPC): See calculated values above

Energy efficiency certificate (EPC)

EnerPHit pre-certificate for stepwise refurbishment (PHI)

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Building owner

Neur Heimat Tirol (NHT)

Architecture / Engineering

Architekt Hanno Vogl-Fernheim


Standortagentur Tirol


Tel : +43.512.576262