A curtain wall system is an outer covering of a building in which the outer walls are non-structural, but merely keep the weather out and the occupants in. Construction costs can be reduced as a curtain wall is non-structural and can be made of a lightweight materials. When glass is used as the curtain wall, the great advantage is that natural light can penetrate deeper within the building. The curtain wall does not carry any load weight from the building other than its own weight. A curtain wall is designed to resist air and water infiltration, sway induced by wind and seismic forces acting on the building, and its own weight forces.
Curtain wall systems are typically designed with extruded aluminum members. The aluminium frame is typically infilled with glass, which provides an architecturally pleasing building while allowing day light in. Other common infills include: stone veneer, metal panels, louvers, and operable windows or vents.
Curtain walls differ from store-front systems in that they are designed to span multiple floors, and take into consideration design requirements such as thermal expansion and contraction; building sway and movement; water diversion; and thermal efficiency for cost-effective heating, cooling, and lighting in the building.