Built in 2012, the Greenhouse is a residential and commercial complex that accommodates Freiburg’s sustainable urban development objectives: it fosters social interactions and is integrative, ecological and cost effective.

The entire design of the building is fully handicapped-accessible, which makes it possible for people challenged by physical, mental or multiple handicaps to maintain their own autonomous households in the complex. Each of the 66 apartments is just as unique and distinct as the needs of the residents: the complex offers everything to small one-bedroom apartments to elegant high-end penthouse suites.

Targeted residence moderation tools support the communicative interactions between the tenants. In some areas, the residents assume responsibility for the decorations in the semi-public parts of the building, which allows them to identify intimately with their living environment.

The ecological quality of the building is also remarkable. Optimum insulation throughout reduces the demand for heating energy to a low level so that the small amount of residual energy required can easily be covered by the geothermal activation of the soil. This method makes it possible to air condition the building year-round: during the summer months, heat energy is extracted from the building and diverted into the soil. During the winter, the system works the other way around: the heat energy in the soil is used to heat the building.

A photovoltaic system on the roof and on the sun-facing facades of the building (peak output 60 kilowatts) helps cover the building’s own power requirements. Solar thermal technology is used to heat up the water for the residents’ hot water needs.

Architekten Frey placed particular emphasis on providing the residents with a comfortable interior climate. The challenge: Given that the interior air quality in many passive solar homes is frequently sub-par due to reduced ventilation intervals. Hence, all windows in the Greenhouse are equipped with a de-centralized room fan with a cross heat exchanger function. This gives residents the option to decide for themselves – at any given time – whether rooms are aired out rooms through the opened windows or ventilated by the exhaust fan function of the cross heat exchanger, which recycles 90 percent of the heat. Moreover, a hygrometer, fine dust and toxin detector also control the individual room fans semi-automatically. Contrary to centralized house ventilation systems, which waste a large portion of the conserved heat energy, decentralized individual room fans air out rooms on an as-needed basis and with optimum precision.

Other innovative architectural details: The sides of the building exterior that do not face the sun are finished as double façade levels in their entirety. All of these facades are enveloped completely by an ensemble of balconies mounted to their fronts and covered with stainless steel webbing, which provides trellises for wall covering creeper plants. The resulting green zones do not only make the building a more attractive place to stay for residents, but also reduce the heat radiation.

Titan oxide has been added to the façade paint as a photo catalyst. By splitting off nitrates, it converts nitrogen oxides into oxygen.

Office + Administration, Residential
Freiburg-Rieselfeld, Baden-Württemberg, Germany
Freie Liegenschaftsverwaltung GmbH
apartment building, six floors
Ecologic features
solarthermics, photocatalysis, decentral single room air handler


(click to enlarge)

front view

view from courtyard