A curtain wall, also known as a facade, can be thought of as a permanent curtain - or cladding - anchored to the interior or exterior of a building. Although curtain wall systems are non-structural, they must be designed to handle loads to which they will be subjected in a given application. For example, exterior curtain walls may be subjected to dead loads, wind loads, seismic loads, snow loads, thermal loads and/or blast loads, and must also prevent air and moisture from penetrating the building envelope.
Earlier curtain walls were constructed of steel, but today aluminum is the metal of choice because it can be easily extruded into virtually any shape imaginable to meet architectural design requirements. The curtain wall assembly can also be infilled, or "glazed" with a variety of materials, including glass, metal panels, stone veneer and operable windows, to name a few. These add functionality, as well as greater architectural interest and beauty.