Because they open up instead of out, single hung windows don't take up exterior space when open. This makes them ideal for areas like adjoining walkways, porches, patios and other high-traffic areas. Single-hung windows differ from double hung windows due to the fact that the upper sash is fixed and the lower sash is moveable. This is the economical version of the double hung. This window has the same features as the double hung, except that only one sash operates and it comes with a half screen.