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U-value

In this page is shown information about insulation values (heat transfer coefficients or U-coefficients) of ETFE air cushion roofs. An ETFE air cushion roof consists of 2 up to 5 layers of ETFE foil. The cushions are fixed to a framework trough a profile system.

The heat transfer through the roof is dependant on the number of foil layers and the profile system applied (the surface area ratio between the cushions and the profiles).

The thermal resistance of the various air layers in the cushions is determined according to table 2 of NEN-EN-ISO 6946.

Calulations are performed according to NEN-EN-ISO 10077-1 and -2, and NEN 1068, unless otherwise stated. The impact of screw connections is compensated by applying an arbitrary value of 0,3 W/m2 K, according to NEN-EN-ISO 12631.

In below tables is shown information about different types of profile systems. Drawings of these profile systems can be found on web page ETFE/detailing.

Table 1 shows heat transfer coefficients for various types of ETFE cushions and profile systems.

Table 1: heat transfer coefficients of ETFE roof system parts

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Typical examples of the heat transfer coefficients of an ETFE air cushion roof system consisting of 10 cushions, each 4 x 20 meter, having a total surface area of 800 sqm is shown in table 2 and 3.Table 2 shows surface area details of the roof with different numbers of layers and profiles.

Table 2: surface area of roof construction parts (size of the roof 20 x 40 meter)

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Table 3 gives the calculated heat transfer coefficents of different types of a complete roof for various configurations (different number of foil layers, i.e. number of air chambers and profile systems).

Table 3: global heat transfer coƫfficients for ETFE roof systems

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