Measuring

• The first step in installing vinyl windows is to take detailed measurements of your existing window frames. This is very important because you want to get a very tight fit to reduce drafts, leaks and be energy efficient. To measure your windows, open them and use a tape measure and go from edge to edge of the window. Be sure to measure right to the window's edge. You'll have to open the lower window frame to do this accurately. Then measure the height from the top of the sill to the bottom. Your windows will be custom made to these measurements.
  
  

Removing the Old Windows

• The next task is to remove the old windows. Take care to preserve as much of the window hardware as possible, including the stoppers used to keep the windows from opening too far. Open the lower part of the window and release the latches that hold it in place. Some windows will remove by tilting forward once you take off the stoppers; others will slide out vertically. Take both windows out of the frame and set them aside.
  
  

Installing the New Windows

• Now install the new replacement windows. Lift the upper window into position between the two window tracks or jambs. Set the bottom part into the track, then slide the rest of the window into place. Lift this window to ensure it fits into the frame properly. Install the stoppers for this window. Then mount the lower part of the window into the frame the same way. Insert the bottom part and then tilt and slide in the rest of the window. The two windows should slide closed and lock together in the middle.