What are single hung windows? The bottom sash of the single hung window moves up to open and allow for ventilation, while the top sash is fixed. Rooms with a view over walkways, porches, or patios, will appreciate this self-contained window whose operation will not interfere with any outdoor living space. Single hung windows are a desirable choice for homeowners looking to conserve the architectural or historical integrity of their home. The difference between double hung and single hung windows is that only single portion of the window is operational.