Forschungsgruppe-NET - Hochschule Offenburg

Solar Heat

District Heating Holzgerlingen, Housing District Hülben

In December 2005, a novel solar thermal system, commenced operation in a housing district of Holzgerlingen; it included a wood pellet stove for warm water and heating support. This CO2-neutral heating system of the housing district Hülben supplies 44 single family homes, 36 apartment units and one kindergarten. The insulation standard of the buildings lies considerably below the Energy Saving Regulations (EnEV).

Apart from the solar thermal system with a collector surface of 248.8 m², there is a wood pellet stove providing additional 540 kW. Three buffer storage tanks are integrated into the heating system to store the heat. 

Since solar power is used for warm water heating and space heating, fuel can be saved thus reducing greenhouse gas emissions as well as costs. 

Immotherm Stuttgart is the operator of this local heating system with integral solar support.

Holzgerlingen was chosen for Solarthermie2000plus for several reasons:

  •  The new roof area is well suited for mounting collectors.
  • The concept was carefully planned and well-thought through.
  • A good demonstration effect.
  • The insulation of the buildings is clearly below the standard requirement of the Energy Saving Regulations.
  • The heating costs were expected to remain below 0.15 €/kWh. 

Project Partners


ImmoTherm GmbH
Heusteigstr. 29
70180 Stuttgart
Ulf Kühn (Managing Director)
phone +49 (0) 711/2381-385
fax +49 (0) 711/2381-382


Local Heating Holzgerlingen
Baugebiet Hülben
71088 Holzgerlingen


EGS-plan - Ingenieurgesellschaft für Energie-, Gebäude- und Solartechnik mbH
Gropiusplatz 10
70563 Stuttgart
Dipl.-Ing. Michael Guigas
phone +49 (0) 711/99007-5
fax 0711/99007-99


Aquasol Solartechnik
Dr.-Carl-Schwenk-Str. 20
89223 Neu Ulm-Burlafingen
phone +49 (0) 731/880070-0
fax +49 (0) 731/880070-48

Friedrich Marstaller GmbH
Lindenstr. 20
72124 Pliezhausen
phone +49 (0) 7127/9799-6
fax +49 (0) 7127/9799-77

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Project Management Jülich on behalf of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety
Berlin Office
Breite Straße 3
10178 Berlin
Dr. Peter Donat
Telephone 030/20199-427

Scientific and Technical assistance

University of Applied Sciences Offenburg
Badstraße 24
77652 Offenburg
Professor Elmar Bollin
Dipl.-Ing. (FH) Klaus Huber
phone +49 (0) 781/205-294

Program Monitoring

ZfS Rationelle Energietechnik GmbH
Verbindungsstraße 19
40723 Hilden
Dr. Felix Peuser
Dipl.-Ing. Reiner Croy
phone +49 (0) 2103/2444-0