The PRO70 ALU Hidden Sash system is a part of the window and door system with thermal break PRO70 ALU. In terms of aesthetics, it is an identical solution to the PRO60 ALU US construction. Its advantage, however, is an increased thermal insulation: the heat transfer coefficient Uf, depending on the profiles and accessories used, ranges from 1.35 to 2.16 W/m2K. This system has a version with increased thermal insulation PRO70 ALU US HI with Uf coefficient in the range from 1.31 to 2.0 W/m2K.
Windows made in the PRO70 ALU US system have sashes invisible from the outside of the building. In the case of adjacent fixed and openable windows, the view of all sections is identical. The width of the window frames is small, so the construction creates the impression of slender and light.
Similarly to the standard solution, PRO70 ALU system windows have an effective system of water drainage and ventilation from the shaft chamber and from the chamber between the sash and the frame. Ventilation and drainage holes on the outside are covered with plastic covers.
The characteristic feature of the PRO70 ALU US window construction is its close connection with other MB series systems. Adopting such a constructional concept allowed to obtain and use many common elements, e.g. common glazing beads, gaskets, fittings, etc.
On the basis of this system, anti-burglary constructions can also be made.