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Thermoanker plays its part in fast build on Germany’s highest mountain

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Every year over half a million people scale Germany's highest mountain, the 2,962m high Zugspitze. Known internationally as the "Top of Germany", its three glaciers and breathtaking 360º panoramic view of Alpine summits across four countries, continue to attract visitors from all over the world. For the less hardy, there are cable car routes up the mountain, but thousands still ascend on foot. And for well over a hundred years, climbers have found shelter in the Höllentalanger Hut, just short of halfway during the initial ascent.

The Höllentalanger, at 1387m, is a 'hut' managed and owned by the German Alpine Club in the district of Garmisch-Partenkirchen, in Bavaria. Since its construction in 1893, the Höllentalanger has grown from a hut into much more of a sophisticated lodge. Despite modernisation over the years however, the building had to be closed in autumn 2013, as it no longer complied with the necessary fire regulations, or requisite health, safety and other standards; making it uninsurable.

A replacement building was needed – and quickly too. Stephan Zehl, an architect from Munich, won the tender with his three-level, stepped building design. It has pent roof borders, which protects against avalanche risk from the eastern side; and meets all necessary current standards in providing dining facilities, equipment rooms, drying and shoe rooms and comfortable accommodation to sleep 100 people.

Everything flown in by helicopter at 1387 metres

After the previous Höllentalanger Hut ceased operation in September 2013, the preparations for the replacement building started immediately with the demolition of the old building. However it was not possible to commence the replacement building process until May 2014. During autumn and winter, all paths to the Höllentalanger are closed-off, as the Alpine climate makes it impossible to work for eight months of the year. Even in good weather, there are only walking tracks to the Höllentalanger, with no road access at all – so everything had to be flown in by helicopter. Rapid assembly and efficient transport costs were therefore critical to the budget and a combination of timber and pre-cast element walls were the chosen method of construction. Core-insulated prefabricated element walls were supplied for the ground level building. These had a special surface texture to resemble natural stone, a feature specified by the architect, to make the building more sympathetic with the surrounding mountain massif. Timber was chosen as a building material for the other levels, which also helps to create the hut's organic appearance.

The pre-cast element walls were installed on site and infilled with concrete. Due to the extreme temperature fluctuations – the temperature difference at this height between air and wall surfaces can be up to 60º C – the concrete is subjected to pretty extreme expansion and contraction conditions. To counter this and to combat thermal bridging, it was important to install Schöck Thermoankers. The units act as both a connecting device and spacer and combine very low thermal conductivity with a high tensile strength; greatly improving the thermal insulation properties of the concrete walls. In total, eleven pre-cast concrete wall segments, each 3.11m x 2.57m were used in the construction, with an average 50 to 60 Thermoankers set horizontally in each element wall, with a further 10 set diagonally.

Innovative GRP Thermoanker

The innovative Thermoanker used at the Höllentalanger is an extremely energy-efficient glass fibre-reinforced connecting device from Schöck. Used for precast concrete cavity or sandwich walls, it is a combined multi-purpose spacer and connector and replaces conventional stainless steel lattice girders.

The Schöck Thermoanker is corrosion resistant, even with thin concrete cover and can be used with any type of insulating material. The product is available in two versions, being suitable for both supported and suspended façades. The TA-H has tapered ends for use in upright, core-insulated concrete walls; and the TA-D, which has straight ends, is used diagonally in freely suspended concrete walls in conjunction with the thermal anchor TA-H.

This Thermoanker solution is a certified Passive House component in the facade anchor category, as tested by The Passive House Institute; and requirements of the EnEV are fully met by its thermal properties. There is also no need for complex thermal bridge calculations due to its low thermal conductivity – Lambda value of 0.7 W/Mk.

The EN ISO 6946 standard regulates the calculation methods for the thermal transfer resistance (R-Value) and the thermal transmission coefficient (U-Value) in building components. In the case of intermittent penetration, it specifies a correction of the U-Value, which usually requires additional calculations by the planner. However, this is not necessary when ΔUf (number of penetrations x intermittent thermal transmission coefficient) is lower than 3%. When thermally assessing the Thermoanker, through the application of three-dimensional thermal bridge calculations, the standard design value of the product is significantly lower than the required limit. Detailed thermal bridge calculations are therefore unnecessary, resulting in significant time saving.

For a free copy of the Schöck Thermal Bridging Guide and / or the Thermal Bridging Solutions brochure – contact the company on 01865 290 890