The next task that windows have to cope with is to dliver sufficient amount of fresh air. To enable inflow of air into interiors the FORIS windows can be furnished with sash tilting and microventilation functionalities controlled by the window handle. However, even closed windows must allow air exchange in rooms e.g. in order to disable excessive concentration of moisture. The infiltration coefficient for FORIS windows is from 0.5 to 1.0 m3.