EnergieWertHaus Rösrath

In 2010 a two-family home was built in Rösrath as an “EnergieWertHaus” eco-house.

Its energy consumption is 30 per cent below the level required by law, for which the new building received the RWE Climate Protection Award in 2012. The sustainable concept was developed by the planner and builder couple Johannes and Dagmar Hermann together with the heating technology manufacturer Vaillant, the construction material specialist Ytong and the inspection service provider DEKRA. The goal was to develop an energy efficient modular system for eco-houses, the design and implementation of which is possible only through certified planners and building contractors.

With a clear architectural language, the house – consisting of two joined cubical shells – fits prominently into the rural surroundings. The new three-storey building takes advantage of the hillside location to create additional living space in the basement. Aluminium floor-to-ceiling windows divide the stuccoed façades and provide for plenty of light inside the building. The combination of three-pane windows and 36.5 centimetre thick masonry of aerated concrete forms an energetically effective building shell.

The heat generation system is likewise eco-friendly. Sufficient energy is extracted via a single borehole to cover the heating and hot water needs by means of a Vaillant geoTHERM brine/water heat pump with a dual buffer tank. In addition, the installation of the Vaillant recoVAIR ventilation system guarantees that no energy is lost here as well, with up to 95 per cent waste heat utilisation. The total annual primary energy consumption of the 240 square metre house is only 34.79 kWh/m2. Even lower, at 13.4 kWh/m2 per year, is the final energy consumption, or the total of room heating and hot water heating. “The consumption levels are more than 10 per cent below the requirements for a passive house,” Johannes Hermann explains.

Construction sign
Designation, name of project:EnergieWertHaus Rösrath
Typology:Multi-family house
Location:Bensberger Straße 325, 51503 Rösrath-Forsbach
Key figures – Area:240 m² living and utility space
Key figures – Technology:34.79 kWh/m² primary energy consumption per year
13.4 kWh/m² final energy consumption per year
Efficiency house KfW55 on the basis of EnEV2009
Key figures – Energy concept:Geothermal utilisation via borehole, geoTHERM brine/water heat pump in combination with Allstor dual buffer tank, in-floor heating, recoVAIR ventilation system
Building owner:Dipl.-Ing. Architecture Johannes Hermann, Dagmar Hermann M.A.
Project developer:Cooperation between Vaillant, Ytong and Dekra
Architect:Dipl.-Ing. Architecture Johannes Hermann, Dagmar Hermann M.A.
YTONG Bausatzhaus Rhein-Sieg-Oberberg GmbH
Technical planner:Dipl.-Bauing. Helmuth Rosenthal

Licence information

Pictorial materialContact
Rights: Dipl.-Ing. Johannes and Dagmar Hermann M.A. / Ytong, photos and drawings can be used free of charge. In case of publication, please send info to:

Dipl.-Ing. Johannes and Dagmar Hermann M.A.
Bensberger Straße 325
51503 Rösrath-Forsbach