The details associated with this section of the BEDG on the WBDG were developed by committee and are intended solely as a means to illustrate general design and construction concepts only. Appropriate use and application of the concepts illustrated in these details will vary based on performance considerations and environmental conditions unique to each project and, therefore, do not represent the final opinion or recommendation of the author of each section or the committee members responsible for the development of the WBDG.
Glass has been used for thousands of years to allow daylight into our buildings, while providing weather protection. The development of the float glass process in the 1950's allowed the economical mass production of high quality flat glass and virtually all architectural glass is now produced by this process. The vast majority of new windows, curtain walls and skylights for commercial building construction have insulating glazing for energy efficiency and comfort. This glazing Chapter is complementary to the other fenestration sections of the Design Guide.
Prior to 1900, windows in the U.S. were predominantly wood frame, with some custom metal windows (iron, bronze, steel) in institutional construction. Around 1900, some British manufacturers of custom metal windows adopted the technology of rolled steel shapes to produce special rail profiles for windows. Two of the more prominent British steel window companies opened U.S. manufacturing companies to produce rolled steel windows. The fire resistance of steel windows with wire glass helped popularize steel window use in the U.S. in the early 1900's. Catastrophic fires in Baltimore, Boston, Chicago and San Francisco led to the development of building regulations that restricted the use of combustible materials in many types of construction. After World War II, the technology of extruding aluminum frames developed and aluminum windows began to gain popularity. By the 1990's, aluminum-framed windows accounted for approximately 65% of the commercial window market. Wood, vinyl and steel-framed windows comprise most of the remaining 35% of the market.
A curtain wall is any exterior wall that is attached to the building structure and which does not carry the floor or roof loads of the building. This includes heavy wall types such as brick veneer and precast concrete panels. In common usage, curtain walls are often defined as thin, usually aluminum-framed walls containing in-fills of glass, metal panels, or thin stone. This chapter addresses this narrower definition of curtain walls. Aluminum framed wall systems date back to the 1930's, and developed rapidly after World War II when the supply of aluminum became available for non-military use.
Skylights have been used for over a century to provide interior daylighting. Early skylight systems consisted of plate glass (later wire glass) in metal frames and frequently incorporated both an exterior skylight and a decorative interior "diffuser" or "laylight". Most contemporary skylights now consist of insulating glazing captured in aluminum frames that in many configuration (e.g. single slope, ridge, pyramid, barrel vault). Skylights are engineered systems that are assembled from standard or custom extrusions provided by skylight manufacturers, and i.g. units made by glazing fabricators, but they share common design elements required to make them perform. This chapter uses the term "skylight" to describe field-assembled systems of sloped glazing. In the construction industry, the term "skylight" is often applied to relatively small shop-fabricated unit-skylights, frequently with plastic glazing. These unit skylights are not specifically addressed in this chapter.
Products and Systems
See appropriate sections under applicable guide specifications: Unified Facility Guide Specifications (UFGS), VA Guide Specifications (UFGS), DRAFT Federal Guide for Green Construction Specifications, MasterSpec®