High Replicability Potential for Austria
In the town of Liezen in the very center of the Alpine Republic Austria, the HAPPENING project took part in the renovation of a multifamily building (MFB) with 20 medium sized dwellings. Its insulation envelope had been retrofitted shortly before.
Before the renovation, the individual apartments were heated by various solutions for both Space Heating (SH) and Domestic Hot Water (DHW): from individual gas boilers and radiators to old stoves and electric boilers.
Ownership of the building lies with the non-profit social housing entity GWS.
The apartments required no cooling function in their system but due to the cold winters in the region, reliable heating was all the more a priority.
Because of the ‘typicalness’ of the MFB, meaning its common kind among building types, there is a high replicability potential.
Lessons learned
- Interface coordination was challenging, possibly simplified by processing via a general contractor.
- Effort and costs for maintenance, system op. & heating bill is rather high.
Key facts
| Building | Heat Pump and Source | ||
| Location | Liezen, Austria | Number of HP | 4 x central 18 x individual* |
| Construction | 1940 | Operation mode | monoenergetic |
| Project type | 2022 thermal renovation | Heat source | air, internal loop |
| Heated area | 980 m² | Type of system | central-decentral |
| No. of apartments | 20 | Cooling | no |
| Level of insulation | good | Type of system | individual HP fed by internal loop fed by central HPs |
| *two apartments were not included | |||
| Heating sytem | Domestic Hot Water | ||
| Heat demand | 77 kWh/m² per year | DHW demand | 35.7 kWh/m² per year |
| Installed power | 126 kW | Max. temperature | 55°C |
| Heating temperature | up to 55°C | ||
| Heat distribution | radiators | ||
| Other information | |||
| COPdecentral | 5.93 | COPcentral | 4.06 |
| Refrigerantdecentral | R32 | Refrigerantcentral | R410A |
| SPF | 2.62 | Back-up heater | in all HPs |
| Climate Zone | Dfb |
Description of the technical concept
As part of the HAPPENING project the refurbishment of the building involved installing a new heating system that relied on a central-decentral heat pump (HP) mix.
Centrally, two air-to-water HPs were installed. By means of a Thermal Energy Storage (TES), they feed a low-temperature water-loop (internal loop) inside the building. On the dwelling level, individual HPs use this internal loop as their heat source for both DHW (incl. DHW tank) and SH (partially using the previously existing radiators).
AT001 – Project HAPPENING Heating Only, Austria