The following are brief descriptions of commonly used curtain wall framing methods and components.
Curtain walls can be classified by their method of fabrication and installation into the following general categories: stick systems and unitized (also known as modular) systems. In the stick system, the curtain wall frame (mullions) and glass or opaque panels are installed and connected together piece by piece. In the unitized system, the curtain wall is composed of large units that are assembled and glazed in the factory, shipped to the site and erected on the building. Vertical and horizontal mullions of the modules mate together with the adjoining modules. Modules are generally constructed one story tall and one module wide but may incorporate multiple modules. Typical units are five to six feet wide.
Curtain walls can also be classified as water managed or pressure-equalized systems. See Moisture Protection below.
Both the unitized and stick-built systems are designed to be either interior or exterior glazed systems. Interior and exterior glazed systems offer different advantages and disadvantages. Interior glazed systems allow for glass or opaque panel installation into the curtain wall openings from the interior of the building. Details are not provided for interior glazed systems because air infiltration is a concern with interior glazed systems. Interior glazed systems are typically specified for applications with limited interior obstructions to allow adequate access to the interior of the curtain wall. For low rise construction with easy access to the building, outside glazing is typically specified. For high-rise construction interior glazing is sometimes used due to access and logistics of replacing glass from a swing stage.
In exterior glazed systems, glass and opaque panels are installed from the exterior of the curtain wall. Exterior glazed systems require swing stage or scaffolding access to the exterior of the curtain wall for repair or replacement. Some curtain wall systems can be glazed from either the interior or exterior.
Typical opaque panels include opacified spandrel glass, metal panels, thin stone, and other materials, such as terra cotta or FRP (fiber-reinforced plastic).
Vision glass is predominantly insulating glass and may have one or both lites laminated (see Glazing), usually fixed but sometimes glazed into operable window frames that are incorporated into the curtain wall framing.