ETFE

Ethylene tetrafluoroethylene (ETFE) is a fluoropolymer used as a transparent film in architecture and engineering. It is a copolymer of ethylene and tetrafluoroethylene produced in thin sheets or foil, which can be used singly or in multi-layer cushion systems for glazing.

ETFE films are characterized by very high visible light transmission, typically around 80–95% depending on thickness, and exceptional resistance to UV radiation and weathering. The material is lightweight, with a low density of about 1.76 g/cm³, and offers good mechanical strength and chemical resistance. It has high thermal stability for architectural use, and when formed into cushions, air gaps provide insulation and controllable shading.

Applications include skylights, façades, and large-span roofs, particularly where light transmission, low weight, and the ability to form into flexible, air-filled cushions are advantageous. ETFE is commonly used in single-layer panels, laminated films, or double-skin systems with pneumatic cushions that can be pressurized for insulation.

History and notable projects: ETFE was developed in the 1960s by DuPont and began widespread architectural use in the 1990s and 2000s. Notable implementations include the Eden Project biomes in the United Kingdom and the Beijing National Aquatics Center, which used ETFE-based envelope systems. It has since been adopted for stadiums, museums, conservatories, and other large-scale structures.

Limitations and considerations include cost relative to glass, potential puncture risk for thin films (though punctures can be repaired), maintenance to retain light transmission and seal integrity, and the need for structural design to accommodate the material’s properties.