A Double-hung window is a window that features an upper and lower window sash that slide vertically past one another in a single casement. Perhaps one of the most traditional styles of windows, this type of window typically features the lower sash in front of the upper sash. Each sash may be a solid pane of glass or may be divided into separate lights by built-in muntins or for decorative purposes, may have a snap-in, removable grid to create the illusion of separate lights.
A double-hung window is designed with two grooves in the side jambs that allow each window sash to slide separate from one another. Some have a full window screen, allowing for ventilation from the top or bottom of the window at any time, while others have only a half-screen that needs be positioned accordingly. The ability to have a ventilation area equal to half of the window’s total area is one reason the double-hung design is so widely used.
This style of window is also a popular choice for replacement windows. It is valued primarily for its versatility. Some of the features that modern double-hung windows have include insulation for improved energy efficiency, tilt-in sashes that make cleaning the outside of the window easy, and UV protection.