A "double-hung" window is a type of window that features two movable sashes, allowing both the top and bottom sections to slide up and down. This design provides flexibility in ventilation, as users can open either sash to control airflow. Double-hung windows are commonly found in residential buildings and are popular for their classic appearance. These windows are typically made of wood, vinyl, or aluminum, and they can be easily cleaned from inside the home. The sash design also allows for better energy efficiency when properly sealed, making them a practical choice for homeowners looking to improve their home's insulation.