The Heliotrope is an environmentally friendly housing project by German architect Rolf Disch. There are three such buildings in Germany. The first experimental version was built in 1994 as the architect's home in Freiburg im Breisgau, while the other two were used as exhibition buildings for the Hansgrohe company in Offenburg and a dentist's lab in Hilpoltstein in Bavaria.
Several different energy generation modules are used in the building including a 603 sq ft (56.0 m) dual-axis solar photovoltaic tracking panel, a geothermal heat exchanger, a combined heat and power unit (CHP) and solar-thermal balcony railings to provide heat and warm water. These innovations along with the favorable insulation of the residence allows the Heliotrope to capture anywhere between four and six times its energy usage depending on the time of year. The Heliotrope is also fitted with a grey-water cleansing system and built-in natural waste composting.