The fifth building material - Maintenance of ETFE constructions

As alternative for glass, ethyltetrafluoroethylene (ETFE) is often used to form pneumatic structures of "cushions".

As alternative for glass, ethyltetrafluoroethylene (ETFE) is often used to form pneumatic structures of "cushions". These constructions can be used for rooftops or other architectural structures. The main advantage is the much lower weight in comparison to glass. Maintenance of small holes and tears can be done with CMC Klebetechnik`s ETFE adhesive tape CMC 77700.

The ETFE is a modified copolymer which is extruded into a thin film. The material is ageing resistant, self-cleaning and transparent. It is unaffected by UV light, atmospheric pollution or weathering and extensive testing has shown an anticipated life expectancy in excess of 40 years (used e.g. for green house cladding). The material is not flammable and it is resistant to normal hailstorms.

Single layer constructions are supported by a cable net. Cushions are formed from multiple layers of ETFE. The foil is extremely thin: each layer is between 50 and 300 µm thick, it enables very high levels of light transmission in both the visible (94-97%) and ultraviolet range (83-88%). Together with light weight perimeter frames it is easily possible to have buildings which appear like as they were built of not much more than air. Architectural roofing designs are revolutionized by these ETFE-films since many years now. Also greenhouses (horticultural and industrial) and wall coverings, anti-graffiti protection for high traffic areas and solar collectors are applications, ETFE is used for due to its excellent properties. ETFE has only 1% the weight of glass, is 100% recyclable and is self-extinguishing.

Despite these advantages of ETFE films there are some problems appearing according to the low thickness of the material. Usually cushions are stabilized by inflating with dry air. Especially on rooftops birds love to land there and peck at their food to break it up before swallowing. The bigger the bird the more powerful their pecking action will be. It is widely known that ETFE roofs and Canopies installed nearby or close to stages (e.g. Allianz Arena Munich) or the sea suffer most of this problem. This is because Ravens, Crows or Seagulls use the ETFE roof membranes as an ideal platform to stop and peck at food rubbish or shellfish, crabs and the occasional stolen chip. This often vigorous and powerful pecking action causes punctures and tearing to the ETFE Membrane, opening holes where the inflating air can leak. This causes higher operation cost or the possibility of fatal destruction of a complete cushion.

Fortunately the ETFE material is resistant to tear growth so that it is easy to repair such holes and tears on-site by using a special adhesive tape. This transparent tape is made of the same material as the cushion itself: an 100µm ETFE-film. The adhesive sticks good to the cushion surface and is similar resistant to UV and weathering as the ETFE. It is resistant against creeping of water under the adhesive tape and elastic as the base material of the cushion.

This is why CMC 77700 ETFE adhesive tape from CMC Klebetechnik is ideal for repairing of damages (minor tears or holes) or reinforcement e.g. under supporting cables of single layer constructions. No need to replace individual elements of a roofing construction can save a lot of money. And due to the transparency of the adhesive tape, repairs are nearly invisible

The fifth building material – Maintenance of ETFE constructions