Schöck Isokorb for Controlling Thermal Bridging

A German system for reducing thermal bridging in commercial construction looks like a real winner.

In commercial buildings where cast-in-place, reinforced-concrete balconies extend through the insulated building envelope, tremendous heat loss occurs, and this thermal bridging often leads to condensation and associated mold problems. The German company Schöck Bauteile, GmbH, has the answer with the Isokorb product line.

How Isokorb works

For thermal breaks in cantilevered slabs (such as with balconies in high-rise residential buildings), Isokorb K provides an expanded polystyrene (EPS) layer of insulation--either 80 or 120 mm (3.1 or 4.7 in) thick--with carefully engineered steel re-bar passing through it to carry the loads. The Isokorb module includes both straight pieces of re-bar at the top that function in tension and specially bent re-bar that functions in compression to maintain the strength that is lost by substituting EPS for some of the concrete (see illustration showing loads and forces).

Special steel is used in Isokorb. Stainless steel 316TI is used both for its corrosion resistance and because it allows just a quarter as much heat flow as standard steel re-bar, according to Alexander Krenczik, the area manager at Schöck.

Range of products available

Isokorb K is available for slab thicknesses ranging from 160 mm (6.3 in) to 250 mm (9.8 in) in 10 mm (0.4 in) increments.

A new product, Isokorb XT, is the only thermal break element that is certified by the German Passivhaus Institut. In Passive House construction, thermal bridging and condensation are high priorities. This particular version is available for slab thicknesses of 160, 180, 200, 220, and 250 mm (6.3, 7.1, 7.9, 8.7, and 9.8 in, respectively).

Different versions of Isokorb are available for other thermal break applications: Isokorb KS is used for concrete-to-steel connections; KSH is used for concrete-to-wood connections; and KST is used for steel-to-steel construction.

Though I'm not a structural engineer, all of these products appear to be fully engineered to standards one would expect from a German manufacturer. As architects get more sophisticated in delivering highly energy-efficient commercial and high-rise residential buildings and as greater attention is paid to ensuring indoor air quality, I believe that Schöck Isokorb will play an important role. The company has been a leader in building component manufacturing to control thermal bridging for 30 years and it has over 400 employees.

The Schöck Isokorb products are currently available in North America through Schoeck Canada, a subsidiary of Schöck Bauteile, GmbH. A Chicago office will be opened later this year. Full technical literature (in English, but with metric dimensions and properties) is available for downloading from the Canadian website.

In 2009, five U.S. projects were completed with Isokorb, but Krenczik thinks that the product will achieve significant market penetration in the U.S. within five years. New educational materials from the company address the LEED Rating System and how the company's products can earn points.

For more information:

Schoeck Canada, Inc.
Kitchener, Ontario
519-896-2100
www.schoeck-canada.com

Alex Wilson is the executive editor of Environmental Building News and founder of BuildingGreen, LLC. His product-of-the week column comes out weekly, as does his Energy Solutions column. To keep up with his latest articles and musings, you can sign up for his Twitter feeds.

See more on this product in the GreenSpec Guide