Thousands of Schöck Isokorb type XT units are being incorporated into the Bahnstadt development, a completely new district being built historic city of Heidelberg, in south-west Germany.

Residentially Heidelberg is very popular and commercially it is very successful, but the city has an expansion problem as there is barely any property to be had. The spectacular solution is to build a completely new district – the Bahnstadt.

The €2 billion initiative is claimed to be the largest single passivhaus development in the world; and when completed in 2022 it will provide living space for some 5000 residents. There will be a vibrant mixture of culture, education and employment. All buildings, not just the 2500 residential properties, will meet advanced passivhaus standards, requiring only 10% of the energy of a conventional building.

With the demands of high insulation levels and the prevention of thermal bridging being critical elements in passivhaus design, the incorporation of balconies has not necessarily been a popular choice with designers. However, the development of the Schöck Isokorb type XT structural thermal break unit has played a major role in resolving that particularly challenging connectivity issue.

Thousands of type XT units are being incorporated into the Bahnstadt development and the major reason for its suitability is the thickness of the insulation body, which is increased from the standard 80mm to 120mm. As a result the unit not only improves thermal insulation performance by up to 30% in comparison to to the standard range, it also improves impact sound insulation by around 50% as well.

A further reason for the superior performance of the type XT is the HTE module, a pressure bearing block made of steel fibre reinforced high-performance concrete with Kronolith, a titanium ore aggregate from Kronos Titan. The unit offers architects and engineers a variety of design options and there is even the capability to construct stepped height balconies, with increased fire protection also taken into account, as the HTE module offers fire-resistance class F 120.

High quality stainless steel bars are also an integral part of the unit. Although there is a smaller rod diameter, the tensile strength is improved and the same load-bearing capacity is therefore maintained. This means a reduction in the thermally conducting cross-section, and an improvement in the heat insulation performance.