Vinyl retrofit windows can be installed into any existing window frame, which significantly decreases the hassle of replacing old windows. The only downside to vinyl retrofit windows is that the existing window frame must be in good condition. If the frame is rotten or broken, then it needs to be replaced before installing the retrofit windows which is a much more complicated job.
To install vinyl retrofit windows, first measure the width and height of the space, not including the frame, where the window is to be installed. Next, work from the interior of the building and remove the inside stop. Save the stop so that it can be reused once the new retrofit window is in place. Remove the old window sash and pane, and the parting stop that runs around the perimeter of the frame. None of these parts can be reused.
Remove the springs or weights in the window frame that helped to open and close the old window sashes. Make sure the frame is clean, then insert the new vinyl retrofit window into the old window frame. Secure the window to the frame using screws, and run a line of caulking around the exterior seam between the window and the frame. Replace the inside stop.