22/10/24

What is movable mullion in PVC window design

As in all other countries, in Egypt windows were traditionally opened by swinging. Having a closer look at such windows, we will see that they do not have vertical mullion typical for a standard design of PVC windows. One sash is closed above another one. Such structures are movable mullion.

 Movable mullion in today's PVC windows is a special profile that is located on one of the sashes. When closing these sashes overlap each other and that ensures the necessary tightness. Movable mullion performs the functions of mullion in standard window structures. The difference between them is that mullion is located on the frame and movable mullion is directly on the sash. 

When window is closed, the movable mullion performs the functions of a central mullion and provides structural strength. Therefore, this element needs to have high strength thanks to good reinforcement of the profile. It increases the weight of the window, however it is absolutely necessary.

Sash of window with a mullion can be opened in any chosen sequence, they are independent from one another. Windows with movable mullion open one after another and sash with movable mullion can be only turn and a second one can have tilt and turn way of opening. The lock in this structure is fixed on the opposite sash.