ULTRA LOW-ENERGY HOUSE COMPLETED IN MUNICH
28 March 2006 - Bayer MaterialScience AG

State-funded energy-saving programs underline a fact long known to private builders: energy-conscious construction is both environmentally friendly and saves money. Top-quality building insulation in particular pays off in the long run, with modest additional costs in the construction phase yielding considerable savings throughout the entire utilization phase, in contrast to the markedly more short-term effects of heating technology. An ultra low-energy house recently completed in Munich shows that high-quality insulation also provides benefits which landlords can enjoy immediately.

The house features the polyurethane heat insulation system PURWALL from Hasit Trockenmörtel GmbH & Co. KG, Freising (www.hasit.de), which interacts intelligently with vacuum insulation panels to lower heating costs. The highly-efficient thin polyurethane foam insulation layers also increases the useable area. The rigid polyurethane foam insulation panels are made by Puren GmbH, Überlingen (www.puren.com) using polyurethane raw materials supplied by Bayer MaterialScience AG. Hasit and its partners have received general building certification for the PURWALL system from the German Institute of Construction Technology (DIBt) in Berlin.

Located in Munich’s Lehel district, the elegant building’s design harmonizes with the new developments extending to its north and south, with no hint of clumsy, functional architecture. Number 23 Seitzstrasse is nonetheless a minor miracle of energy-saving technology. The building, which is part-funded by the City of Munich and houses offices, business premises and apartments, can boast an energy consumption of only 20 kWh per square meter per year. That is equivalent to just two liters of heating oil per square meter per year. The “two-liter house” therefore uses only one tenth of the energy consumed by the average building in Munich, and also clearly undercuts the ambitious low-energy house standard (40 to 60 kWh per square meter per year). If it wasn’t for the fact that the ultra low-energy house in Seitzstrasse is in the shade of its neighbors, it could even compete with true passive houses (less than 15 kWh per square meter per year). The ultra-low energy house was recently awarded the Bauphysik Prize 2005. This prize is awarded for outstanding and innovative achievements in the field of building physics. The jury were particularly impressed by the way space could be optimized through the trend-setting use of vacuum insulation panels and the holistic energy concept.

The structured plaster is applied to the outer surface.
Insulating the building’s exterior walls plays a key role in achieving these excellent results. At 23 Seitzstrasse this task is performed by thin vacuum insulation panels (VIP) combined with a layer of rigid polyurethane foam insulation just eight centimeters thick that are rated in TCG (thermal conductivity group) 030. These are manufactured by Puren using polyurethane raw materials from Bayer MaterialScience. To connect the insulation and the exterior wall in a way that does not create a heat bridge, a vital factor, strips of the solid polyurethane material Purenit, also from Puren, were cast into the concrete of the wall construction. These serve as anchoring points for the bolts used to fix the upright, moisture-resistant polyurethane panels to the building’s exterior wall.

To insulate the fixing elements on the plaster side, approximately two-centimeter-thick disks were cut from the polyurethane insulating material and re-inserted after the panels had been screwed on. Thanks to this innovative technique, the fixing elements are completely encased by the insulating material. The sensitive vacuum panels are fitted in the space between the concrete wall and the polyurethane heat insulation system created using Purenit spacer pieces. The polyurethane insulation layer provides the panels with maximum protection against damage. To avoid further heat bridges, the polyurethane insulation panels are connected using bonded tongue-and-groove joints.

The polyurethane insulation material’s particular strength becomes clear when its insulating thickness is compared with other materials. To provide the same insulation as the eight centimeter-thick polyurethane panels, around 12 centimeter-thick wood fiberboard (TCG 045) and around 11 centimeter-thick EPS panels (TCG 040) would be required. The leaner exterior wall design made possible by polyurethane adds 8.1 square meters of useable area or 10.8 square meters of living space over five floors. With rela estate purchase prices in Munich at around EUR 4,000 per square meter, the building owner gains space worth over EUR 30,000 for almost nothing. This gain more than offsets the additional investment for the polyurethane insulation and the extra space increases the rental income that can be expected. Tenants won’t complain either, given that the reduced heating costs will save them cash, too.

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