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# Screws according to EN ISO 12631

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# Screws according to EN ISO 12631

In this lesson the definition of a periodically existing screw as an equivalent 3-dimensional object is explained and critical points are emphasized. The equivalent lambda values for equivalent 3-dimensional objects and bordering air cavities are calculated directly by flixo according to EN ISO 12631 depending on distances, dimensions and hidden materials.

In the next step you will define a screw as an equivalent 3-dimensional object of a mullion construction. Following the calculation you will check the critical material key values of the cavities.

Click on the arrows in the graphic below to navigate in lesson 8.

Screws according to EN ISO 12631

Summary

Select all objects of the screw with the Select, Move, Scale tool. By pressing the Shift key the selection is extended continuously with every further mouse click.

Periodically appearing screws or objects with rectangular shaped cross section can be defined with the command Edit.3D equivalent Object > Define. You can adjust the material, the kind (screw or rectangular cross section) and geometry materials (radius and distance respectively depth and distance) which are necessary for the calculation of the equivalent conductivities in the opening dialog window.

The material of the background regions can also be assigned afterwards with the Drag&Drop function, the material of the equivalent 3-dimensional object can be adapted in the Properties flyout or in the corresponding

Hidden lines subdivide the screws (respectively the object with rectangular shaped cross section) into  regions. The cavities which border to the screw form one single air cavity for which the equivalent key values are calculated according to EN ISO 10077-2. The subdivision of the screw into several parts has an essential influence on the results. In our example the joint U-value enlarges for 0.1 W/m2K if the screw is not subdivided into several parts. The subdivision of the equivalent 3-dimensional objects occurs where the object penetrates punctually another region.