Even more transparency without visible support structures on the facade is one of the most important trends in modern glass architecture. Since 2010, Glasstec has regularly organized the “Engineered Transparency” conference to discuss the latest developments. Christoph Rubel, technical director of Edgetech Europe GmbH, was one of the speakers at the 2021 event. His input on the contribution of the flexible spacer Super Spacer® to the creation of facades with large curved insulating glass elements can also be applied to the Våghuset in Gothenburg and the Nordstrom flagship store in New York .
The facade recalls the maritime heritage
Gothenburg and Hamburg have a lot in common: major seaports, idyllic canals and sensational and sustainable urban development projects in the former free port areas. Anyone wishing to rent the fully glazed, BREEAM-certified Våghuset commercial and office building in Gothenburg's new Masthuggskajen district signs a voluntary commitment to the responsible use of employees, energy and materials.” The elementary façade impressively demonstrates how glass can be used as a creative design tool while achieving its energy goals,” enthuses Joachim Stoss, Vice President International Sales IG at Quanex.
Towards the city center, the building with rounded corners features elegant reflective windows made up of curved cylindrical elements, which recall waves with two-tone stripes and the lively alternation between concave and convex; a tribute to the Göta älv river, on which Gothenburg's importance as a port city is based and which flows here into the Kattegatt.
The “Wave House” is a true European project
According to facade specialist Staticus, which is itself one of the largest full-service facade contractors in Northern Europe, “Våghuset is a shining example of European collaboration.” In fact, the project was signed by the largest Scandinavian architecture firm White Arkitekter of Gothenburg, the facade was created by Staticus in Lithuania, the curved profiles were produced in Denmark and the windows in Germany and Poland. The Swedish company NCC AB was responsible for the development and construction of the project.
“The fact that Heinsberg spacers are also used in curved insulating glass elements is mainly due to manufacturing reasons,” explains Christoph Rubel, “Only flexible spacers such as Super Spacer can precisely follow the curvature of cylindrical glass. Since curved glass insulation is practically always made by hand, it must also be possible to apply the spacer manually.”
Flintermann Glasveredelungs GmbH from Lower Saxony had delivered around 300 curved insulating glass units to Lithuania for installation. They consist of 2 x 5 mm laminated float glass with SunGuard® SNX 60 solar control coating, 20 mm TriSealTM Super Spacer® Flex and 10 mm float glass. Like standard double glazing, Guardian highly selective glass lets in 60% of natural daylight, but only 29% of solar heat. Therefore, additional sun shading can be dispensed with in Våghuset.
“The peculiarity of this project was the gradual transition from concave to convex. Most of the units had a step all the way around. The internal glass was always smaller so that it could be recessed into the unitary façade,” explains Robin Dorn, head of curved glass sales at Flintermann.
Sustainability as a driving force for facade design
“Staticus is not only the Scandinavian market leader for large-scale facade projects, but also a driving force for intelligent and energy-efficient facade solutions,” explains project manager Saulius Visockas. “Våghuset fits this philosophy perfectly. We are grateful that especially Northern European customers like NCC fully support our sustainable approach.”
The combination of WICTEC EL evo for the element system and 50SG for the transom system allows for the appearance of a homogeneous flush-mounted structural glass façade. Perimeter lighting is integrated into the facade profiles on all 13 floors to make the shape of the building visible even in the evening and during the winter months.
Single glazing with matt Blackpearl coating up to 1.563 mm high and up to 2.688 mm wide are installed in front of the thermal insulation. Clear window strips consist of insulating glass units up to 4.307 mm high and up to 2.441 mm wide. A Ucw value of ≤ 0,5 W/m2 was specified for the flat triple façade elements and a Ucw value of ≤ 0,65 W/m2 for the double curved elements. At the same time, even in Nordic conditions of -15°C and wind load of 3,4 m/s outside and +20°C/30% RH inside, condensation must under no circumstances form on the glass .
Curved insulating glass without vertical supports
The connection between Gothic cathedrals, whose structures create lightness, light effects and transparency so impressively, and modern glass architecture has often been drawn. The use of glass, also as a structural element, to maximize the penetration of daylight is now a fact. But the question of how to take this transparency to the extreme with increasingly larger glass and without visible mullion and transom structures continues to worry architects, facade engineers and the glass industry. Larger pane sizes naturally mean thicker glass and less light transmission. Curved shapes, which provide greater rigidity even with thinner glass due to the supporting effect of the shell, are often the solution.
“Today, cylindrical curved insulating glass is taking on more and more load-bearing functions to avoid vertical support posts or beams in the facade structure,” says Christoph Rubel. The gap between the panes must be kept as small as possible to meet the high thermal insulation requirements and at the same time achieve a tight, vertical glass edge seal. Furthermore, while curved insulating glass units are stiffer, they are also more sensitive to climate loads such as wind and solar radiation.
In the facade of the Nordstrom flagship store, which is located on the podium of the Central Park Tower in New York, a total of 254 glass elements up to 6 m high form the individual floors without any visible vertical connection. The architectural firm James Carpenter Design Associates was responsible for the design of the 45 m wide and 38 m high facade at the corner of Broadway and 57th Street.
“Making glass of this size is an art. One of the few glass benders in the world who has mastered it is Cricursa,” explains Christoph Rubel. In Nordstrom's case, 4-layer laminated glass with narrow radii and a ceramic frit surface was produced using a gravity bending process. “Since the edge bonding is elastic thanks to the flexible spacer, the spacer also does not absorb countable climate loads. This has the advantage of not placing stress on the edge bonding.” To be on the safe side even when it comes to seismic risk, facade consultant Surface Design Group has incorporated a lateral slip joint into the curved profiles to give clearance to the glass elements when subjected to large loads.
Super Spacer® flexible spacers can also be applied by robots in automatic lines. Joachim Stoss concludes: “Large format and expensive insulating glass elements must be produced with high quality and precision, often with three or even more panes, to meet thermal insulation, safety or acoustic requirements. The larger and heavier the insulating glass, the more difficult it is to handle during production. Super Spacer holds the edge seal in position practically immediately after application and guarantees maximum precision and parallelism of the sheets in both automated and manual processing .
About Edgetech Europe GmbH, a part of something biggerSM
Edgetech Europe GmbH, headquartered in Heinsberg, Germany, is a wholly owned subsidiary of Quanex Building Products Corporation, (NYSE: NX), a publicly traded global manufacturing company primarily serving OEMs in the window, furniture, solar, refrigeration and outdoor markets. Edgetech Europe GmbH serves the continental European markets with a total of 490 employees and 17 extruders. We are “a part of something bigger” by improving the performance and aesthetics of end products through continuous innovation, helping customers achieve greater manufacturing efficiencies and giving back to the communities in which we operate. Visit quanex.com for more information.
