Curtain wall systems are exterior wall assemblies that do not support building loads but provide weather protection and aesthetic appearance. The system consists of aluminum framing, glass or metal panels, and seals. The aluminum framing (mullions and transoms) is attached to the building structure at vertical and horizontal intervals. Attachment points typically occur every 2 to 5 feet horizontally and 5 to 10 feet vertically depending on wind loads. The framing provides channels for holding glass panels (typically insulated glass units) or opaque panels. Insulated glass units (IGUs) consist of two or more glass panes separated by a spacer bar, creating an insulating air or gas-filled cavity. IGU performance depends on frame and spacer quality; warm-edge spacers reduce heat loss compared to metal spacers. Opaque panels may be metal, composite, or stone veneer. The curtain wall system is sealed to prevent water infiltration. Glazing seals typically consist of gaskets and sealants. Primary seals prevent water entry; secondary seals provide backup and accommodate movement. Thermal breaks in the aluminum framing prevent heat transfer between inside and outside, improving energy efficiency. Testing of the curtain wall system verifies watertightness and wind resistance. Water testing involves spraying water while pressurizing the wall system to verify no leakage. Installation requires experienced curtain wall installers and coordination with other trades for flashing at penetrations and connections to floor systems.