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From a water tank to the Aquaturm Hotel

First zero-energy high-rise building of the world is being built with innovative EJOT insulation support anchors according to passive house standard

The family Räffle is realising an ambitious building project and is setting an energy efficient signal directly on Lake Constance. For the first time worldwide a closed water tower will be rebuilt to a zero-energy high-rise. "Probably it will even be a plus-energy high-rise", architect Norman Räffle explains, because the pilot project is using all regenerative energy sources such as geothermal energy, solar energy, photovoltaic and wind energy. The building is considered to be a demonstration facility of the Federal Republic of Germany and is promoted by the Federal Environment Ministry with funds of 435,000 Euros.

Thanks to intelligent energy-saving solutions, sustainable raw materials and high-quality fastening elements, the Aquaturm Hotel is a showcase project: The elevator in the stair tower for example features a construction for energy recovery. The concrete components have been made with slag sand from granulated blast furnace slag. The use of slag sand causes less CO2 emission in the production of cement. The building insulation will be fixed with passive house-suitable insulation support anchors.

The regenerative facade will cause highest attraction because its surface will be mostly covered with solar panels. Exactly speaking it deals about a rear-ventilated facade system in combination with a fleece-laminated heat insulation and energy generation from photovoltaic elements.

Energetic landmark

The completely scaffolded water tower in Radolfzell. On the left the separate supply tower which has already been thermally insulated. (Image: EJOT)


EJOT sponsors over 5000 insulation support anchors

The building project is supported by various manufacturers from the building sector. EJOT has supplied the new insulation support anchor DH for fixing the thermal insulation. The two-part anchors fulfil the high energetic demands of the pilot project. By means of subsequent tube assembly, the insulation support anchors prevent the so-called "quilt effect" which occurs due to the point-cast impressions of the insulation when traditional one-part anchors are driven too deep into the substrate. Additionally they prevent the joints between the individual insulating panels at the joining edges from gaping. "The insulation support anchors from EJOT are easy to work with", Norman Räffle knows, who has already used about 2,200 anchors for a 100 mm-thick insulation on concrete. Further 3000 anchors will be needed for a 240 mm-thick insulation on a solid brick substrate. Thanks to the two-part principle of the anchors an utmost efficient installation of a two-layer insulation becomes possible.

Family project "Aquaturm"

The tower for water supply for the near milk production was built in 1956 and closed again in 1979. Norman Räffle was already fascinated of the water tower as a child. He has always had the idea that there could be made something great of those industrial remains. First drawings arose which he showed his father, the entrepreneur Jürgen Räffle. The young man was so much fascinated of the water tower that his building plans gave reason for his profession and he studied architecture. His brother Thorsten Räffle as financial expert set a business plan for the family project, so in 2002 their father finally bought the building for 25,000 Euros as family property.

They broke ground in 2008, because of the economic crisis in 2009 the building process was stopped for that time. Under the name "aquaturm" the project finally could be continued in 2011. In total the reconstruction will cost about 2.5 m Euros. "If you think about the project only economically, you must not do it at all", Jürgen Räffle says, who as autodidact has developed a passion for building and construction. Just looking at the Räffles tells us that they associate idealism, heart and passion with the project of the Aquaturm. The rather long building time can be explained by the fact that the building project is almost completely realised on their own performance.

Altogether the tower has been expanded from 30 to 46 metres. The final height of 50.5 m will be reached by the vertically rotating wind turbine. The weight of 2500 tonnes is borne by the 15 m deep foundation piles. In accordance with the original use the water tower will stand in a 22 x 11 m big water basin.
Computer animation of the Aquaturm with solar panel facade and wind turbine. (Image: Räffle)