Vögelebichl multi-family houses, Innsbruck
The buildings are the first in the world responding to highest efficiency standards. Furthermore, the buildings were designed to achieve the annual net-zero energy balance thanks to on-site renewable energy generation. In addition to the heat pump, solar energy is used to power the two blocks.

Lessons learned
- Vögelebichl was designed as a net-zero energy building (NZEB), thus, to achieve the annual net-zero energy balance thanks to on-site renewable energy generation. Although the balance has not been achieved in the monitored years, simulations showed the possibility to achieve it.
- However. the net-zero balance would be obtained thanks to the large PV yield surplus during the summer, which might be a problem for the grid stability and it is not so effective in reducing the building specific CO2 emissions. Therefore, the net-zero balance on an annual basis might be a misleading approach to ensure low CO2 emissions.
Key facts
Building | Heat Pump and Source | ||
Location | Innsbruck, Austria | Number of HP | 1 |
Construction | 2015 | Installed power | 44 kW |
Heat distribution | underfloor heating | Operation mode | monoenergetic |
Heated area | 2149 m² | Heat source | Groundwater |
No. of apartments | 26 | ||
Heating sytem | Domestic Hot Water | ||
Heat demand | 17.9 kWh / (m²a) | DHW demand | 26 kWh / (m²a) |
Heating temperature | – °C | Type of system | central |
Max. temperature | – °C | ||
Other information | |||
PV installation | yes | COP | 4.7 |
PV yield (electric energy) | 12 kWh / (m²a) | SPF heat pump | 3.1 |
ST yield | 19.9 kWh / (m²a) | SPF heat generators (HP and ST) | 4.9 |
Description of the technical concept

The building’s HVAC system consists of two parts: the hydronic system and the ventilation system. The ventilation units ensure hygienic air renewal, whereas the hydronic system provides low temperature space heating (SH) and DHW preparation with decentral fresh water heat exchangers connected to a central heat pump (HP) and solar thermal (ST) collectors. The HP is double-staged – allowing it to work at two levels of power – and provided with an additional heat exchanger, i.e. the de-superheater (DSH). The purpose of the DSH is to deliver heat at a high temperature level (e.g. heat for DHW) while not raising the condensation temperature (simultaneously delivering SH), thus at higher energy performance. Heated system-water is stored in a combi-storage tank from which it is withdrawn for SH and DHW preparation. If stratification is properly ensured, combi-storages offer the possibility to save costs and reduce storage losses.
The advantage of storing system-water rather than hot drinking-water, which is prepared in the flats by decentralized DHW heat-exchangers, reduces the temperature at which the water must be heated to avoid Legionella growth, allowing for better HP performance and thus energy savings. The south building (S) roof is completely covered by PV, while the north building (N) is covered partly by ST and partly by PV panels to ensure the on-site electricity generation for achieving the net-zero energy balance.
AT001 Vögelebichl