ETFE roof is
What is ETFE?
Ethylene Tetrafluoroethylene, ETFE, is a kind of new generation plastic having high chemical resistance and mechanical strength over a very wide temperature range. It is a very molecularly stable material. The strong bonds that exist between the fluoroplymer molecules avoids the degradation of the material due to atmospheric conditions, substances deposited on the material or ultraviolet radiation.
Having 25-30 years of durability, color stability and resistance against becoming brittle, ETFE, with its unparalled alternative to traditional materials, is used successfully for heat insulation and sun control at the façades and roofs.
Advantages of ETFE
Thanks to its lightweight characteristic compared to alternative materials, considerable saving on the weight of structural steel can be achieved.
Despite its high transmission properties, right transmission levels for light and UV can be easily obtained by using various ETFE films.
Its high chemical resistance ensures over 20 years of life even in harsh climatic conditions.
Its strong molecular binds provide a clean surface throughout its life. It does not need any protective top coat.
Especially applications with 2 or 3 layers provide much higher heat insulation than comparable systems.
ETFE folio has passed the fire resistance tests for International Standards.
There are various types and printed ETFE folios for control of light and UV.
Unique visual impacts can be easily obtained by ligth and projection.
Its high light transmission and heat insulation properties provide considerable savings on energy costs.
High chemical and mechanical resistance keeps the material clean and strong throughout its life.
Cost saving is approximately 40% lower compared to conventional transparent roof constructions.
Mechanical Properties of ETFE
ETFE foils have a very high durability compared to other transparent plastic materials. High tensile strength, extraordinary tear and impact strength of ETFE foil are the basic properties of an ideal membrane material. ETFE is a very ductile material and demonstrates good failure behaviour thanks to its large deformations before breaking point. ETFE foils are also alkali and solvent resistant to a great extent.
|Tensile Strength||50 MPa||DIN EN ISO 527-1|
|Tensile Stress at 10% Strain||21 MPa||DIN EN ISO 527-1|
|Tensile Strain at Break||600%||DIN EN ISO 527-1|
|Tear Resistance||500 N/mm||DIN 53 363|
|Opacity||7.5%||DIN 53 363|
Why ETFE instead of Glass?
|Visible Light Transmittance (%)||90.5||82.4||75.4||88.9||79.6|
|Ultraviolet Transmittance (%)||83.5||71.5||62.3||61.4||45.5|
|Heat Transmittance (W/m2K)||5.8||2.6||1.7||5.8||3.3|
|Acoustic Transmission (under 100Hz)||3.0||4.6||unmeasured||17.7||20.0|
Compared to glass, ETFE film is lighter, transmits more light and is also resilient. Its properties like self-cleaning due to its nonstick surface and recyclability at lower cost are superior. When using pressurised pillows, it’s possible to achieve control of both sunlight transmission and effective insulation. ETFE coverings offer also excellent acoustic properties, as the material does not cause annoying echoes indoor. Unlike glass ETFE film is shatterproof,
Thermal and Chemical Characteristics of ETFE
A standard three-layer cushion has a U-value of around 1.95 W/m2·ºK. This is considerably better than triple glazing when used horizontally. The cushion’s insulative characteristic can be further enhanced by addition of further layer which can also be treated with Low E coating. This approach could reduce the U-value to below 0.6 W/m2·ºK.
ETFE foil also absorbs a large proportion of infrared light transmitted, a quality which can be used to improve energy consumption of buildings.
Light Transmission of ETFE
The optical characteristics of the transparent ETFE foil are very advantageous. Alongside its low weight, the major benefit of ETFE is its high translucency by transmitting up to 94-97% of visible light (380-780nm) and 83-88% of ultraviolet range (300- 380nm). This is a vital property for well being of humans and plants. The nearly natural daylight makes the indoor environment more enjoyable in projects like shopping malls, indoor swimming pools, atrium roofs, market places, football stadiums and tennis courts.
ETFE cushions can be lit internally with LED lighting to make them glow or projected onto externally like a giant cinema screen, creating dramatic results.
Design of ETFE systems
ETFE foil roofs can be supplied as a single layer membrane supported by a cable net system or commonly as a series of pneumatic cushions made up of two to five layers of ETFE. Whether it is a single layer or in cushion forms, ETFE foil systems are supported in an aluminium extrusion at the perimeter which, in turn, is supported by the main building frame. In the case of ETFE cushions, they are kept continually pressurised by a small inflation unit which maintains the pressure at 200-600 Pa and gives the foil a structural stability and the roof some insulation properties.
At ONART, we possess the experience that can only be acquired from years of dedicated service within the industry. Although we are constantly looking for ways to improve our company, we never forget our firm foundation built on a tradition of reliability and quality. We identify opportunities for the projects to differentiate themselves and deliver innovative design solutions. We strive to seamlessly integrate enhanced engineering solutions in our design process, while always keeping in mind the cost effectiveness.
Shading with ETFE systems
Whilst base material is very transparent, ETFE foil can be treated in a number of different ways to manipulate its transparency and radiation transmission characteristics by adding more layers, printing, tinting, surface treatments and radiation.
It is also possible to control the amount of light that is transmitted to the inside by combining 1 translucent and 2 printed ETFE films into a 3 layer design and moving the middle layer up and down. Through this approach, maximum shading or reduced shading can be achieved as and when required. Essentially, this means that it is possible to create a building skin which is reactive to the environment through changes in climate. In such systems the middle layer is programmed to rise and fall (using air pressure) to increase and decrease the percentage of printed area and therefore control solar gain.
Fabrication of ETFE systems
As foil membranes have a predefined width, patterning have to be done to form the surfaces. Continuous welding of ETFE Foil defines the quality of seam of the patterns.
Cushions are made by combining two, three or more layers of foil which are joined at their edges and inflated with air to form a sealed panel. The internal pressure in the cushion prestresses the foils enabling the cushions to withstand external loads such as snow and wind. The pressure inside the cushions is borne primarily by the outer and inner layers. Cushions are normally held in an aluminum extrusion frame and used as part of a cladding system.