They are definitely measured differently. The insert window you would measure inside the existint window frame, which in most cases is built out of 3/4" lumber all the way around. For a full replace ... read more
Since 80% of a window is glass, it is always wise to pick the right glass for the direction the window faces in your home. LowE 366 Argon filled glass for the south and west exposures may be the best ... read more