Stanovanjsko podjetje Zagorje

Zagorje ob Savi, Slovenia

Multi-family building | 112.5 sqm installation



This assessed multi-family building has a centralised heating system connected to a biomass district heating system but sanitary water is heated locally with electric energy. In order to have also environmentally friendly and more economical sanitary, for hot water heating a central solar thermal system was proposed. It was proposed to install solar collectors into a roof rather than on a construction despite an un-optimal roof orientation.
The solar system with flat plate collectors and thermal power of 78.7 kWth leads to 62 % of energy savings for sanitary water heating. In addition 60 tons of CO2-emissions will be avoided per year.



Type of building

Multi-family building

Number of dwellings, floors

45 dwellings
5 floors

Year of construction


Total effective area (heated)

2,100 m2

Hot tap water consumption

1,600 m3/a

Whole energy consumption for heating purpose (present situation)

not available

Proposed CSTS (main variant)

Type of collectors

Flat plate collectors

Thermal power

79 kWtherm.

Aperture area of collectors*)

112.5 m2

Buffer storage


Hot tap water storage

6.0 m3

Total capacity of boilers

300 kW

Type of hot tap water heating


Type of heating system


Estimated Costs

Total cost solar system

63,400 Euro

Cost of the CSTS/gross area of collectors

564 Euro/m2

Available Subsidies

0 %

Predicted System Output

Output of solar heat

60000 kWh/a

Reduction of final energy

60000 kWh/a

CO2-emissions avoided

60.6 t CO2/a

*) Aperture area = light transmitting area of the front glass


Proposed System Scheme



Stanovanjsko podjetje Zagorje
Cesta zmage 16b
1410 Zagorje ob Savi, Slovenia

Assessment by 

University Ljubljana
Faculty of Mechanical Engineering
Askerceva 6
1000 Ljubljana, Slovenia
Phone: +386 1 4771234



This assessment summary (English)

354 K


Detailed assessment report, 12 pages (Slovenian)

2.5 M