Which type of window is designed to slide open vertically?

A sash window is specifically designed to slide open vertically, typically consisting of one or more movable panels (sashes) that can be raised or lowered within a frame. This design allows for effective ventilation as air can enter from the bottom while warm air escapes from the top when the window is opened.

In contrast, a casement window is hinged on one side and opens outward, usually providing excellent ventilation but not in a vertical manner. An awning window is similar, but it is hinged at the top and opens outward, creating an awning effect rather than sliding. Lastly, a picture window is a fixed glass window that does not open at all, serving purely as a means to provide a view or natural light without any functional capability for opening. Thus, the characteristics of a sash window clearly distinguish it as the only option intended for vertical sliding operation.