ETFE
ETFE structure
ETFE (ethyl tetra fluoro ethylene is a strain of fluoro polymer) foil is lightweight (it weighs 1% of the equivalent-sized glass panel), highly transparent to UV light, is not degraded by sunlight, has better insulation properties than glass, is recyclable and can take up to 400 times its own weight.ETFE is different to PVC and PTFE fabrics as it has no base cloth substrate; it is an extruded film or foil. Typical construction is via an air supported pillow and pneumatic system (additional infrastructure including fans, dehumidifiers and control modules) or cable net. Spans for pneumatic ETFE pillows are limited to 4-5 metres.
As with PVC, ETFE fabrics have excellent fire ratings but are combustible (fire retardant). In general, fire ratings are not a major concern for open structures as the toxic fumes are dispersed by natural ventilation.
ETFE is recyclable and decreases energy costs by around 30% when compared to glass, due to its capacity to allow in more natural light and heat retention properties. ETFE film is lightweight and provides excellent light transmittance. ETFE maintains transparency and strength for over 30 years. Dust and dirt does not settle on ETFE easily. However, if it does, there only needs to be a small amount of rain or water for the surface to be cleared of dirt and grime.
Configurations
ETFE foils commonly come in two forms: two and three layer (and more) pneumatic pillows or cushions, or as a single cable supported layer. When used as a pneumatic pillow, the cushion is restrained in aluminium extrusions and supported by a lightweight structure. The cushions are inflated with low pressure air to provide insulation and resist wind loads. The pneumatic construction resists external forces through the difference in internal and external pressure. Multilayered ETFE pillows also provide great thermal resistance which can be as effective as glass. Additionally, printed ETFE foil can provide target Shade Coefficients.Single Layer ETFE
This configuration provides a unique visual effect, similar to the two and three layer configurations. The façade and roofing application is most common, with U values still reaching as low as 5.2U(W/m2K).Double Layered ETFE pillow
This configuration provides efficient insulation with U values as low as 2.3U(W/m2K).
Triple Layered ETFE pillow
This configuration provides superior insulation with U values as low as 1.5U(W/m2K).
ETFE foil is acoustically transparent with a mass of less than 1kg/m2. As a result, it does not reflect internally generated noise back to the occupants. The internal environment is considerably more comfortable with shorter reverberation times than if the cladding had been constructed from an acoustically hard material. This intrinsic feature of ETFE means that cost intensive counter measures, such as the integration of acoustic absorbers into the internal walls, are usually unnecessary. Furthermore, with a sound reduction index of less than 10dBA, the ETFE envelope can provide increased comfort levels and encourage occupants to make full use of the space.
