Extra outstanding appearance, a wide variety of shapes, high light transmission and long lifetime characterise the ETFE foil inflated roof- and facade covers.
When covering light-demanding spaces and buildings, among the tensioned membrane structures, it is the single-layer or multi-shell inflated cushion systems of ETFE foil that are used increasingly to replace glass. Inflated systems have a wider use in this product group, since this design significantly improves the energetic properties of the covered roof or facade sections: thermal insulation and thermal absorption can be easily and safely controlled through the thickness of the air chamber between the layers both in summer and winter setting.
Printing the foil layers with silver pigments is an important property in the aspect of energetics. Silver pigments reflect the sunlight, making significantly less heat to enter the closed system. Printing the foil layers and the controlling of the air chambers make it easy to handle different angles of solar exposure, that is, screening effect and heat-reflecting effect can be adjusted according to the time of day.
ETFE foil is an ethylene tetrafluoroethylene polymer without substrate textile and with increased tolerance against environmental contaminations; the plastic particles of the foil have increased tolerance against UV radiation and against most chemical compounds as well, making the obsolescence of the material very slow. No dirt, dust or other contaminations adhere to the foil thanks to its smooth surface, making it easy for the rainwater to clean the ETFE surfaces.
Areas covered by ETFE foil cushion can exploit the advantages of natural light due to its great light transmission properties, making artificial lighting less required.
ETFE foil cushion systems are used often for covering zoological- and botanical gardens, since these systems transmit the UV light, providing the adequate habitat for plants and animals. In case of covered pools, natural tan is made possible by sunlight transmitted through the membrane roof even in winter.
Just like in the case of other materials used for membrane or other lightweight covers, the diverse exploitation of technical lighting opportunities works for ETFE foil systems as well.
It can even be used to replace glass surfaces thanks to its light weight, making the supporting structure thinner.
ADVANTAGES OF ETFE FOIL CUSHION SYSTEMS
- Lightweight, relieved supporting structure
- Versatile application for the energy control of buildings
- Provides good acoustics
- Increased tolerance against UV, but still transmits UV rays through
- Self-cleaning surface
- Visual effects
- Exceptional thermal insulation: 1 layer: 5,7 W/m2K*, 3 layer: 2,94 W/m2K*, 5 layer: 1,18 W/m2K* (* Indicative data, different for each project!)
Extruded foil from the group of ETFE (ethylene tetrafluoroethylene) fluoropolymers without substrate textile; material thickness of 80 to 500 microns; light transmission of 85 to 95%; no changes in mechanical properties under temperatures between -200°C and +150°C; fire classification: B-s1-d0.
STRUCTURE AND SHAPES
It is necessary to mount so-called secondary supports on the basic supporting structure even in the case of ETFE foil inflated systems; a special aluminium rail will be mounted on these secondary supports using bolted joints (the rail is used to fix the foil cushions). The cross-section of the foil cushion and the height of the cushions depend on the number of layers and on the amount of air between the layers. However, the shape of each cushion piece can be triangle, rectangle, hexagonal or octagonal depending on the geometry of the primary steel supports. The foil cushions usually do not necessarily need support up to a span of 4 to 6 meters, however, in case it is necessary, wire rope support should be installed where the cushions are subject to constant snow- or wind loads.
The individual air supply of the cushions can be provided constantly from the air handler unit located outside, through a ventilating duct system. The air supply is provided by the air handler unit located outside, which is equipped with an automatic controller and dehumidifier.
The manufacturing process of single-shell or inflated systems of ETFE foil is similar to the manufacturing process of products of other similar materials, however, the welding process is different from the usual.
Material testing protocols and test assessment shall be adapted to the project before cutting; the treatment of the materials during the cutting, the method of cutting (manual cutting or PC-controlled cutting with automatic cutter) and the determination of compensation values are all different. Each cushion layer is prepared and cut to shape individually - this is the way to ensure the planned cushion geometry intended to have after the welding of the layers.
The cut pieces of different sizes are assembled with so-called welding seams, by applying contact welding process, with the permanent binding of two foil layers, and without the application of intermediate materials. The rail edge required for the fixing of the cushions and the special valve for the air supply will be established in this stage. The air flow between the chambers can be controlled by the perforation of the intermediate layers.
In the final stage of the manufacturing, that is, in the stage of folding and packaging, the foil cushions are folded and packed in accordance with the order of on-site assembly and technology. The cushions should be delivered as rolled on a paper tube - without folding, and avoiding piling them on each another.
Graboplan provides the following services with regard to the manufacturing of ETFE foil cushion systems:
COUNSELLING, CONTRIBUTION TO THE PLANNING
The advices of our experienced engineers and manufacturing specialists concerning the structural, anchoring and air supply / mechanical requirements of the ETFE foil cushion system should be taken into consideration at the stage of concept planning.
DEVELOPING THE CONCEPT, FORM-FINDING
The ideal membrane shape is developed by taking the local conditions – structure, anchoring, meteorological loads, roof type – into consideration with 3D form-finding analysis.
Preparation of scale model: before finalising the concept, it is possible to prepare a life-sized model to eliminate occasional planning errors and technical solutions that wouldn’t work in practice.
SELECTION OF MATERIALS, DETERMINING METHOD OF ANCHORING, AIR SUPPLY SYSTEM
The material strength, quality and type of load-bearing and intermediate layers can be specified on the basis of preliminary static calculations, after the assessment of material tests. The design and strength of anchoring can be finalised on the basis of the material, the type of the primary support, and on the basis of the preliminary static calculations.
The air handler unit required for air supply is designed in this stage as well.
ESTABLISHING THE BUDGET
The budget for a project’s roof or facade cover can be established after determining the foil strength, the method of anchoring and after designing the air supply system.
DATA PROVISION FOR AUTHORISATION PROCEDURE
We prepare the membrane drawings, data provision concerning dynamics and preliminary designs for the authorisation design documentation of the construction as agreed.
PREPARATION OF PRODUCTION PLANS
The manufacturing of the tensioned membrane and of the anchoring will be performed on the basis of elaborated plans approved by the customer.
PREPARING PRODUCTION PLAN AND ASSEMBLY CONCEPT
Simultaneously with the selection of materials will the preparation of the manufacturing technology and assembly concept start, which, among others, shall include the performance of tests before, during and after the production, the determination of product control processes, procedural and final inspections, manufacturing technology, welding processes, folding and packaging concepts, the manpower and machinery needs of the on-site assembly, and the elaboration of proper assembly technology.
Technology and manufacturing capacities adapted to the dimensions and technical requirements of the project, using state-of-the-art machines: each ETFE piece is cut with CAD/CAM computer-controlled plotter machine, and then the assembly and the permanent binding of the pieces is ensured by welding units designed for the welding of special ETFE foils.
We arrange the delivery of ordered products to any part of the world with shipping by road, by air or by sea.
Our group of experienced mechanics will perform the assembly of our tensioned membranes in any country of the world, under the supervision of Graboplan project managers: our mechanics have IRATA certificates, they are qualified to perform work at height, to operate machinery, they have personal protective equipment and special equipment for assembly.
PREPARATION OF DELIVERY DOCUMENTATION
Preparation of as-built drawings, specifications of materials installed, technical data sheets, declarations of performance with product-related user-maintenance instructions.