When we bought brand new double hung windows, we requested full screens instead of half screens so we could open the top or bottom of the window without sliding the screens around. Our screens were $70 each (would have been cheaper for half screens) but came with a lifetime warranty and they fix holes, rips, etc. at no cost. If you already have the frames it would be worth just buying the roll of screen, some spline, and a spline tool and trying to do it yourself.