Which type of window has a side-hinged sash that swings outward for ventilation?

The type of window that features a side-hinged sash which swings outward for ventilation is known as a casement window. This design allows the sash to open fully, creating a large opening for airflow, thereby providing excellent ventilation. The mechanism usually involves a crank or handle, making it easy to open and close the window from the inside. The outward swing is particularly beneficial as it allows for unobstructed views and air flow, especially in breezy conditions.

Single-hung and double-hung windows do not have sashes that swing outward; instead, they either slide vertically. The horizontal sliding window also operates by sliding, but from side to side rather than swinging open. Therefore, the unique outward swinging action of casement windows distinguishes them from the other types listed.