Extruded ETFE Foils for membrane roofs


With the refurbishment and expansion of Salzburg’s main railway station, which first opened back in 1860, the Austrian Federal Railway (Österreichische Bundesbahnen – ÖBB) is continuing to expand the trans-European rail network. The design for the refurbishment by Aachen, Germany-based architects Kada Wittfeld combines the listed platform roof with a modern foil cushion roof construction. Ceno Membrane Technology processed the Nowoflon ET 6235Z foils made from the high performance 3M Dyneon ETFE polymer into an elegant, highly transparent construction.

Platform roof with a modern foil cushion roof (photos: 3M)

Salzburg main railway station has linked two states since it opened back in 1860: the kingdom and empire of Austria-Hungary and Bavaria. Extended several times, it was both a through station and a terminus at which several lines ended for over 100 years. As part of the expansion of the trans-European rail network, the ÖBB Infrastruktur Bau has worked since the end of 2008 to transform the main railway station into a high performance through station that is used by an average of 25,000 passengers every day. The historic station building and steel arches over the platforms have been retained.

Modern roof construction

The construction of further platforms called for an extension of the roof. Architects Kada Wittfeld prevailed in an international tender. Their design complemented the three historic steel roofs renovated in 2009 with two around 300m long roof constructions made from pneumatically-supported foil cushions. Ceno Membrane Technology based in Greven, Germany was responsible for planning, calculating and installing the filigree construction. The company has been one of the leading companies in the field of textiles architecture for more than 30 years now and has successfully installed sophisticated membrane constructions around the globe. Installation of the three roofs took place in two stages, which were completed in 2012 and 2013 respectively.

Design freedom through a low area weight

The two membrane roofs span an area covering around 6,000m2 and comprise a total of 161 triple layered, compressed air supported foil cushion elements. Assembled across the platforms, the domed cushions span widths of up to 4.5m and lengths of up to 24m.

The two membrane roofs span an area covering around 6,000m2 and comprise a total of 161 triple layered, compressed air supported foil cushion elements.

The Nowoflon ET 6235Z foils extruded by Siegsdorf, Germany-based Nowofol Kunststoffprodukte for the Salzburg main railway station are just 250 to 300µm thick, highly transparent to visible light and UV-light. The fluoropolymer film provides a good combination of properties that makes it a suitable material in membrane construction, for instance, good mechanical strength, particularly tear strength and tensile strength and good weatherability.

Another advantage is that the area weight is around just one twentieth of that of glass. This allows for filigree constructions, opening up new degrees of freedom in architectural form. Ceno Membrane Technology used continuous heat pulse welding methods to process the foils and insert these into individually constructed aluminium frames.

Transparent and durable foils

Foils extruded from Dyneon ETFE are said to have a low energy surface, meaning a normal rain shower is generally sufficient to wash off any dirt, which reduces the maintenance costs. The Dyneon ETFE material shows virtually universal chemical resistance and meets the B1 fire class criteria (according to DIN 4102).

The area weight is around just one twentieth of that of glass, which allows for filigree constructions.

As highly transparent foils, they allow more than 90% of the visible light spectrum to penetrate. Depending on the application, the Nowoflon ET 6235Z foils can be produced in almost any RAL colour and a variety of thicknesses. The tensile foils do not require any plasticiser or stabilisers, and are said to retain their favourable properties for decades and to be robust and durable in all climatic zones.




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