What is the difference between a window wall and a curtain wall?

A window wall is formed by a window with any kind of external casing, including rigid or flexible construction. The curtain wall, on the other hand, is an integrated building exterior composed of masonry units with windows and doors. A curtain wall may be composed entirely of masonry units, but typically includes some glazing material as well.

Both are structural elements for buildings that are distinguished by their material composition. However, windows are regularly used in structures that do not need the security offered by the solid walls found in some buildings. Window walls provide protection against intruders and fire spread without compromising visibility inside or out for occupants; curtains can also provide protection against fire spread but may obscure views inside or outside buildings.