Internorm came out with the beautiful KF 520, a system that combines innovative design with technical know-how. The window sash is not visible from outside due to its glass appearance and can optically not be distinguished from fixed glazing. This sash also contains the revolutionary locking I-tec Secure which renders levering of the window impossible – unrivaled in the branch. Integrated flaps press on all sides into the frame interior when locking and thus ensure maximum burglary protection.

  1. The window insulation (Thermal Insulation) prevents heat loss and also helps regulate the surface temperature of the interior glass. It also makes it possible for heated homes to maintain a higher humidity level, and thus better air quality, with a reduced risk of condensation on the windows. The thermal insulation of a window depends on the frame material, the glazing, and the impermeability. The parameter is the U value – the lower the figure, the better the thermal insulation.  The KF 520 is an amazing example of just that.
  2. Noise can be very unpleasant to have to compete within your home. Noice can have a major impact on the human body by causing sleep deprivation and general disruption in your life. However, Internorm windows bring their incredible insulated frames and acoustically engineered glass that provides a solution to the problem.

    The level of sound reduction is a window is measured in decibel (dB. The higher the decibel number, the more soundproof a window is. So as we see in the diagram to the right, the KF 520 can have a dB of 33-46. A great level of sound reduction. The level Soundproofing a window can boast is dependent on the frame material, the type of glass, permeability of the window, and the construction connection.

  3. I-tec Secure locking is unrivaled on the window market and makes the UPVC or UPVC/aluminum window KF 520 the top product concerning security. Instead of the customary locking pegs, flaps undertake the precise locking of the window sash with the frame. I-tec Secure is integrated into the KF 520 as standard and achieves security class up to RC3.This flap also offers considerable advantages when cleaning the window. Only a few parts on the sash protrude, closing elements are omitted almost completely, leaving a smooth and easy to care for UPVC surface between the parts.

    The advantages:

    • Perfect security available up to RC3 due to integrated flaps
    • Locking flaps arranged in short distances on all four sides
    • Levering of window practically impossible
    • Nice appearance as no visible closing elements
    • Easy cleaning of the window frame
    • Modern glass architecture due to narrow view width

Next, I would like to add a diagram so you can all get a better idea of the technical features of the KF 520:


Dimension (in mm)

Frame construction depth – 90 mm
View width frame/sash – 85 mm
View width flying mullion (2 sashes) – 96 mm
View width transom/mullion (2 sashes) – 148 mm


*Due to printing and manufacturing technology color deviations between”illustrations in this blog and original products may occur.”  Internorm by GSW Team will gladly show you original samples.



More details on the KF 520: 


KF 520 is an amazing product. You can play around with colors and designs both at the same time. Our GSW Team would be more than happy to help you design your special and unique home. Give us a call or send us an email with your project and let us make your dreams come true.