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Kameha Grand Bonn sets standards in hotel construction

The Kameha Grand Bonn won the MIPIM Award 2010 in the category “Hotels and Tourist Resorts” at the international real estate fair MIPIM in Cannes and is thus one of the world’s best real estate projects. The technically and creatively sophisticated lifestyle hotel breaks new ground in terms of design and function. In the unusual outer skin, Kalzip profiled sheets form the watertight layer almost invisibly, clad with composite cassettes.

The building is situated on the banks of the Rhine on the site of the former cement works. The Bonner Bogen district has been under development here since 2003, following the plans of the architect Karl-Heinz Schommer. The operator of the new hotel is the Lifestyle Hospitality & Entertainment Group of Frankfurt am Main. The client is the BonnVisio group. The hotel has 254 rooms, of which 62 are suites, seven bar and restaurants and a spa area with outdoor pool. A glazed event hall up to 18 metres high is the heart of this building and forms the access to the terrace area situated on the Rhine side.

“Grand Hotels have always been the world leaders in technical innovation”, explains Carsten Rath, operator and initiator of the Kameha Grand Bonn. The name Kameha comes from a Hawaiian king and means “the unique one”.

The 100 million Euro arch-shaped building is innovative and unique in many respects. According to the architect, the smooth steel and glass construction is meant to emulate a water wave. This wave rises up to five floors high and approximately 60 metres wide over the gently sloping bank of the Rhine. This form is emphasised by a cladding of large-format sheets made of silver-grey aluminium and the delicate glass cover between the two wings of the building. The six large recesses in the roof were implemented as terraces, one of them with an outdoor swimming pool. With a symbiosis of passive solar power, intelligent cooling systems and a resource-preserving air conditioning concept on a geothermal basis, the Kameha Grand Bonn fulfils the requirements of a sustainable energy supply. The hotel is supplied with heating and cooling via a geothermal system with an aquifer storage system, which optimises the energy yield by means of separating summer and winter operation. The basic load supply takes place via concrete core activation in the ceiling systems. Floor convectors with a fresh air supply cover the additional requirements. An air-conditioning floor provides for pleasant temperatures all year round in the glass hall. The hollow sections of the metal construction are filled with water and serve as heating or cooling surfaces respectively.

Supporting roof cladding

The Kameha Hotel was constructed on individual and strip foundations in the good load-bearing gravel layers. The two basement storeys lying on top had to be secured by tension rods against buoyancy in the case of flooding of the Rhine. The rising conical construction consists of steel reinforced concrete in a cross-wall construction. The curved outer skin was implemented as a load-bearing layer over all storeys and dimensioned as a supporting shell structure. In order to achieve freedom from columns as far as possible, particularly on the ground floor, wall-like beams and restraining devices with composite girders and columns were developed.

Kalzip standing seam system as a watertight layer

The structure rises on a conical floor area with the widths 68 m / 60 m and a length of 104 m as well as a roof ridge height of 24 m. The roof is formed as an arch and passes over into the likewise arch-shaped facades. The roof and the facades each consist of a combination of glass areas and metal elements. The execution of the roof and facades placed high demands on materials, engineers and tradesmen. Numerous complex details had to be developed by those involved in order to safely implement
the outer skin of the hotel, with its many upstands, recesses and joints from the base on the north side to the base on the Rhine side in the south, both technically and in terms of building physics.The aluminium roof stands on the supporting steel reinforced concrete shell.

In order to ensure the vapour-tightness and air-tightness of the building, a vapour barrier was applied first, on top of which the variously dimensioned top hat profiles, which serve to accept the Kalzip clips, were anchored in the steel reinforced concrete ceiling. A 240 mm thick mineral thermal insulation layer provides for the required U-value.

Subsequently, the aluminium profiled sheets were mounted onto the system fasteners provided. The small seam of the profiled sheet thereby latches into the system fastener and is covered by the larger seam of the next profiled sheet. Both are finally positively connected and zipped to one another mechanically.

Kalzip profiled sheets in the overall widths 50/429 and conical 50/350-460 were used with a plated, stucco-embossed surface. The profiled sheets were produced in the factory in straight, tapered and roll rounded variants
precisely in accordance with the requirements for the combined roof and facade construction. A total of 4,860 m² of roof and facade area were installed.

Support with penetration-free fastening

In order to produce an outer skin with a smooth appearance, in which the large-area joint pattern stands in context to the glass facade design, it was decided to support large-format Reynobond cassettes, an aluminium composite material, on the Kalzip standing seam system.

The cassettes measure up to 6.73 m x 1.60 m. Kalzip has the advantage that, due to the penetration-free mounting of such supports, reliable water drainage is always guaranteed even in the case of complex details and such large formats.

“The composite sheets were mounted by means of an intermediate construction made of extruded aluminium sections over seam clips, which could be supported on the tried and tested Kalzip roof cladding on the seams without penetration”, explains Christian Trenks, Application Technology Manager at Schüngel Metal Systems GmbH, Altenburg, which carried out the laying
of the roof and the facade construction. “Due to their size, the Reynobond cassettes were manufactured in our own production with glued-in supporting and stiffening aluminium sections”, explain Trenks. Building Authority approval in an individual case was obtained for this.

Summary

Unusual projects like the Kameha Grand Bonn also require unusual solutions. In order to constructively solve the unique continuous roof and facade shell with its numerous recesses and to permanently seal it, the only building material to come into question was one that fulfils the highest standards, technically and from the point of view of building physics. Thanks to their high flexibility and individual formability, the Kalzip profiled sheets proved here once again their outstanding characteristics when it comes to realising sophisticated architectural concepts. They adapt to any desired form and can be installed quickly and simply.

Thus Kalzip products always guarantee a sustainable roof and facade solution
that convinces economically as well.