When deciding between and single and double hung window there are many things to consider, but the four you will see mentioned most often are in regards to price, ventilation quality, energy efficiency, and cleaning.
Price – If your primary consideration is price, you will probably want to opt for the single-hung window. Single-hung windows use fewer components and are easier to manufacturer. This keeps their cost down.
Ventilation – Single-hung windows have a fixed-top sash so that only the lower sash can be opened. With double-hung windows, both the lower and upper sash is operable. By way of ventilation, the windows are equal in the amount of open space that can be attained. However, with a double-hung window the ventilation can be from the bottom sash, the top sash or a combination of both.
Energy Efficiency – While most windows are manufactured to strict quality-control standards, it is not uncommon to have some air gaps or leakage. Single hung windows are likely to have less of these issue for the sole fact that the have fewer moving parts and, therefore, less opportunity for air gaps. The fixed panel in the single hung window is virtually airtight.
Cleaning – Double-hung windows are typically designed so that the operable sash can tilt inward for ease of cleaning. The operable sash of a single-hung window will do the same, but the fixed sash will not. This means that you will have to reach the outside of the single-hung window in order to fully clean the glass. This is particularly noteworthy for windows above ground level.