In a renvoation project I installed 14 Vetter double hung 44 inch alum clad windows with low E glass, one was tempered. Of the 28 frames (top and bottom) 15 have warped and bowed and make it impossible to shut the windows with the seals in. This problem was reported to the distributor shortly after installation and it's taken nearly a year to get the vetter representative out. Despite the warranty and product defect, their response is, "there are so many, would the owner pay for half". This is insane. The Vetter rep says the tolerance on warp and bowing is 1/4 inch. With 1/4 inch bow, the windows will not close!