ETFE (Ethylene Tetrafluoroethylene) film is extremely durable, totally transparent, fully color printable, and considerably lighter in weight than glass structures. ETFE is rapidly establishing itself as the overall best value option for skylight applications, large-scale natural light green housing, transparent long-span structures, and architectural building facades.
ETFE Construction Technology
Single Layer ETFE
ETFE can be applied in a single layered form and are reinforced with either wire cables, light weight steel or aluminum to maintain shape and stability.
In a double or triple layered application, ETFE film incorporates a pneumatic system to maintain air between 2 or 3 layers of film attached in aluminum extrusions and supported by a lightweight structure creating inflated cushions. These cushions are filled with low-pressure air, providing thermal insulation and structural stability against wind or snow loads. If needed, small cables can be used for reinforcement. Under typical loading conditions, ETFE cushions can range from 5 to 15 feet wide and reach up to 200 feet in length.
ETFE film is unchallenged among building materials in terms of aesthetic impact and visual presence whenever a structure simply must stand out as a unique statement of functional art. With design flexibility that far exceeds that of other structural fabrics, ETFE can also be paired with colored lighting, providing the ability to produce a completely different look and feel at the touch of a button. Whether your intent is to add a statement piece to permanently differentiate your corporate headquarters from your competitors’ or to cap off an already impressive design with your personal architectural signature, Big Span’s ETFE film structures are the absolute best medium for bringing the boundless potential of your own creativity to life.
Benefits of ETFE Film Structures
Exceptional Light Transmission
ETFE films can be highly transparent (from 90% to 95%) and allow for the passing of UVs responsible for promoting photosynthesis, thus facilitating plant growth.
ETFE film systems can incorporate several frit patterns on one or multiple layers to alter their solar performance. The foil is printed with various standard or custom patterns. Colors can be introduced in various ways, whether applied during the film extrusion process providing a consistent tint in various tones from red to violet or adding lighting with unlimited color options.
While ETFE films are very elastic (up to 600% at breaking point), they are still structurally resistant. The tensile strength at the limit of elasticity/plasticity is 21-23 N/mm² but tensile strength to breaking point is 52/Nmm². For structural calculation a limit of 15 N/mm² is conservatively usually taken.
Under exposure to environmental pollution, UV light, harsh chemicals or extreme temperature variations, ETFE does not degrade.
ETFE film has approximately 70% acoustic transmission
From extruding of the film to transportation to site, compared to other similar cladding materials, little energy will be consumed thus reducing the overall carbon footprint. In addition, the product’s nature enhances the building physics through insulation and daylighting, therefore contributing to the global low energy aspect.
Due to the lightweight nature of ETFE, substructure support systems and concrete foundations can be designed more efficiently. ETFE systems also provide ample natural daylighting, thus minimizing energy costs by lowering the demand for indoor lighting.
Easily recyclable, waste from the manufacturing process or even old ETFE elements can be remolded into new ETFE products such as tubing components, wires or castings.
Comparable to a glass system, the increased thermal performance is possible with a multi-layered system. For a double or triple-layer pneumatic system, multiple layers of film are welded into panels that are inflated with low pressurized air to stabilize the film and providing the thermal property of the system.
In a single-layered application, you can achieve about an R-Value of 1 and in a two-layer system, approximately an R-Value of 2.0. Whereas, a three- layer ETFE system has an R-Value of around 2.9 degrees F h / Btu or a U-Value around .35 BTU/(h degrees F ft 2).
Air Inflation System/Energy Consumption
A pneumatic ETFE cushion system is generally supplied by one or more inflation units. Each unit consists of two (2) redundant blowers forming a backup system for guaranteed structural stability. The air when entering the machine will be dried to avoid condensation within the cushions. A series of pressure sensor will continuously monitor the internal pressure of the ETFE cushions maintaining them between 5 PSF and 6 PSF. In case of high wind or snow loads, if necessary and designed, sensors can automatically and continuously adapt the pressure to compensate external loading up to 30 PSF.
Depending on air temperature and humidity, one unit can supply a roof of up to 15,000 square feet. These units are UL certified and run on an 110V power with power consumption less than 1kW/h.
Photovoltaic and LED Integration
Flexible photovoltaic (PV) cells and/or LED lighting can be integrated with either a single layered or cushioned system to meet performance and/or aesthetic requirements.
Due to the non-adhesive surface properties of the ETFE, deposits of dirt, dust, and debris do not stick and are washed away by the rain resulting in a “self-cleaning” effect. However, as for all mechanical equipment and their components, it is necessary to perform a yearly inspection. The inspection includes all necessary checks on the air inflation units and filter replacements. The ETFE film and its attachments will also be inspected for possible damages to prevent any further issues.
ETFE Films have been rates under different national and international standards as self-extinguishing with no burning drops. The film melts away at around 500 degrees F. They are classified under several world standards as ASTM E84 class A, ASTM E108 class A, UL 94VTM class 0, EN 13501-1 class B-s1-d0, NFPA 701.
Due to the high resistance and elasticity of the ETFE, it is an ideal building component where sudden extreme loads such as earthquakes or blast may occur. Unlike glass that will shatter and cause major concern under similar shock load situations, ETFE will either deflect under load or even in case of breakage, is unlikely to cause any major damages. ETFE is, however, not suitable as vertical railing and cannot prevent from intrusion.