What is the difference between a welded frame and one that is screwed together?
When a vinyl window frame is welded it means that the corners of the frame and sash have actually been fused together. This makes for a very strong window and does not allow for any air infiltration because there are no open seams. A window that is screwed together at the corners is not as stong and the potential for air infilration is greater because the seams are not fused.