Single Hung Windows open and close by moving the lower panel or sash of the window. Thus, only half of the window area can be opened for ventilation. This is the most traditional-looking style of window.
Double Hung Windows are virtually the same as single hung windows except that both the upper and lower sashes can be moved. The advantage is that you can adjust the sashes so that warmer air escapes at the top of the window opening while cooler air enters from the bottom.
