More than any other building material, uPVC windows and doors made of Koemmerling profiles keep their excellent material properties even after many years in use. As a matter of fact, they do not alter under extreme temperature or weathering. Thanks to the Koemmerling owned material compound of the uPVC profiles, they show no negative effects caused by heavy rain, snow, strong sun or smog. They also do not rot, corrode nor warp. And even after many years, the windows are still attractive, perfectly tight and working well.