Without a doubt the most effective and efficient way to improve your windows is the full replacement process.  Many replacement window companies offer insert windows, which are generally less expensive, but don't offer the full range of energy efficiency as full replacement windows do.  While Natelli Homes does offer insert windows, we much prefer to replace the entire window frame and re-insulate around the entire window, just as it would be installed in one of our renovations or new homes.  Just evaluate the insulation that is injected around this Eagle full replacement window before the new clad brick mould and shutter is applied - it's not hard to see and understand why this is so much more effective.  You won't get this type of installation in the insert replacement window process.  Our Marvin window replacement process offers the same energy efficiency.