100% design.
100% comfort.
0 energy.

Being on the move and causing as little harm to the environment as possible.

Our family-run hotel is not only the highest hotel building on the lake but also offers many other superlatives in terms of sustainable construction and energy efficiency.

Here you can find out which measures we use to keep your ecological footprint as small as possible during your holiday or business trip, without you having to sacrifice comfort or luxury.


The building supplies itself 100% from renewable energy sources:

  • Hydrothermics
  • Photovoltaics
  • Solar thermal energy
  • Wind power
  • U-wall: 0.129 W/m²K, U-ceiling: 0.134 W/m²K, U-floor: 0.142 W/m²K, U-window: 0.44- 0.47 W/m²K
  • Heating heat requirement: 26,000 kWh/a (37 kWh/m²a)
  • Hot water heat requirement: 23,800 kWh/a (33.7 kWh/m²a)
  • CO² savings: 78,000 kg/year (vs. ENEV 2012)
  • PV: approx. 34,000 kWh/a (average yield 600kWh/ kWp)
  • Wind: approx. 1,000 kWh/a
  • Solar thermal energy: approx. 20,000 kWh/a (total heat demand approx. 40%)
  • Geothermal heat: 30,000 kWh/a
  • Geothermal cooling: 17,000 kWh/a (24 kWh/m²a)
  • Elevator Power consumption: 5,221 kWh/a- 1,513 kWh/a Energy recovery= 3,708 kWh/a (5.3 kWh/m²a)
  • General electricity demand: 41,000 kWh/a (57 kWh/m²a)
  • Passive house Building envelope with integrated PV modules (1000 pcs.) Reduced thermal bridge constructional component connections
  • High-performance composite windows 5x glazed as aluminium/wood construction with weather-protected sun and glare protection and
  • passive summer rear ventilation
  • Full vacuum tube collectors with solar protection function as an integral part of the facade
  • Seasonal solar heat storage tank made of glass fibre Vol. 10,000 l with layer charging technology
  • Lithium iron phosphate storage 52,5kWh, usable 47,25 kWh m. Three-phase connection 63A
  • Power-controlled, highly efficient water feed pumps
  • Decentralised ventilation units with heat recovery > 90%
  • Decentralised hot water concept with fresh water stations, tap temperature max. 42°.
  • Hydraulic and route-optimised pipe network, highly thermally insulated
  • Most economical water tap (0.7l/min.-1.75l/min.) in the world
  • Economical Rainshower shower systems m. 8,0l/min.
  • Floor heating/cooling with intelligent individual room control (dew point sensor) and ceiling fan support
  • Passive heat and cold mass storage (ceiling + walls) for night cooling and solar heat radiation
  • Vertical rotating wind turbine as building top with lowering hydraulics
  • Elevator with PU belt drive and energy recovery technology and energy-saving stand-by control
  • Presence-controlled lighting with 100% LED technology
  • Gastronomy: Heat recovery from kitchen exhaust air, hot water connection of all kitchen appliances to solar and heat pump
  • Undercounter refrigerators a. Hotel room w. A+++
  • 2x ground water duplicates for free-cooling operation of the building (thermoactive surfaces + ventilation) and recooling function for solar thermal system
  • Highly efficient, modulating water-to-water heat pump with solar energy utilisation JAZ >5
  • Freely programmable heating and cooling control
  • Digital energy data monitoring to determine and optimize energy consumption

Among other things, real woods, recycled wood materials, natural stone floors as well as lime and clay plaster are used for the interior fittings. The clay plaster (colloquially known as healing earth), which consists of 100% natural raw materials, improves the comfort and air quality of a room like no other product due to its unique properties such as pollutant and odor reduction, massive water vapor absorption and release capacities and its antistatic effect. Decentralised ventilation systems with highly efficient heat recovery (>90%) ensure a controlled exchange of air containing CO² with oxygen-rich outside air, which is treated by an F7 filter to remove fine dust and pollen.

The basis for the development and conversion of this building is the intention to operate the existing building stock (75%) as well as the new building area climatically adapted and comfortable with the lowest possible use of resources and energy.
Since the planning, construction and operation of highly efficient buildings such as the aquaTurm, the importance of “grey energy” for the construction of the building is given much greater priority. In this project, significant resource savings were achieved compared to a structurally identical, conventional new building through the following measures and products:

  • CO2 reduced concrete (CEM IIIA/B blast furnace slag)
  • Preservation of the tower stock (75% of the mass) vs. new construction
  • Rock wool insulation vs. glass wool/ EPS insulation
  • PV modules (CIS) vs. polycrystalline modules
  • Wood-aluminum windows vs. plastic windows or aluminum windows
  • Interior fittings – complete furniture with recycled wood components
  • Interior plaster pure clay vs. gypsum plaster
  • Substitution of concrete and steel components by wood and recycled substitutes


Through regional, sustainable and responsible added value in the project conception, it has not only been possible to develop a building with an ecological model character, but also to consider economic and social aspects. This is achieved through the Räffle family’s own immense contribution and the awarding of contracts to local specialist companies and national product manufacturers, as well as the moderate limitation of their own return and growth targets.

Social affairs

The water tower in Radolfzell on Lake Constance was built, like many other water towers, in 1956 for water storage. The tower was closed down in 1979, which meant that it lost its function as a high-level water reservoir. More than 30 years of decay have left unmistakable external traces and obliged us to put this production-intensive, unused structure to a new use. Above all, the breathtaking view should be made accessible to the public, in order to make the citizens aware of the unique landscape in which we all live.

Only the touristic use of the building will enable the integration into the urban and social environment.

The aquaTurm can justifiably be called a crazy family project. Over a planning period of 20 years and a construction period of 7 years, more than 80% of the work to be carried out was carried out by the Räffle family with only two employees. Nearly all the building products used in the aquaTurm come from Germany. Above all, the knowledge and experience gained during the planning, construction and operation of the aquaTurm is passed on in many ways through energy house tours in the aquaTurm, specialist lectures and scientific connections to universities.

It is only through our motivated and cordial staff that the aquaTurm is brought to life as a family-run hotel. Our employees are the heart and soul of the aquaTurm and are the most important thing for our hotel business with its guests. For this reason, we let our employees share in the economic success of the hotel through success- and health-oriented work and pay salaries that are above the standard rates.

We offer sustainable luxury and comfort with a clear conscience.

Sustainable travel

Stay in one of the most energy efficient hotels in the world!