According to the RAL requirement, it must be "internally more vapour-tight than outside" in order to meet the requirements for energy saving, longevity and an optimal room climate.
The window's position is equally important, as incorrect positioning can lead to a high level of relative humidity that persists for extended periods of time. This can cause problems further down the line, with condensation forming in the most serious cases. Anyone making lazy compromises during the positioning and sealing process risks consequences such as moisture damage and mould.
According to the 3-level model, joints are:
Multifunctional tapes are able to seal joints at all three levels with just one product. Nothing is faster, more economical and safer.
Alternatively, window joints can be sealed with three individual products using impregnated joint tapes for the external and internal joint. Since there are numerous requirements for tapes, the tapes are subdivided into different groups (DIN 18542 by Beuth Verlag) with regard to external application, these are BG1 or BG2 or BGR.