A curtain wall is an outer covering of a building in which the outer walls are non-structural and merely keep out the weather. As the curtain wall is non-structural, it can be made of a lightweight material reducing construction costs. When bent glass is used as the curtain wall, natural light can illuminate the building. The curtain wall façade does not carry any dead load weight from the building other than its own dead load weight. The wall transfers horizontal wind loads that are incident upon it to the main building structure through connections at floors or columns of the building. A curtain wall designed with bent glass can resist air and water infiltration.
The French hothouse at the Jardin des Plantes, built by Charles Rohault de Fleury from 1834 to 1836, is an early example of a bent glass curtain wall architecture.
By far the most common glazing type, a bent glass curtain wall can be of an almost infinite combination of color, thickness, and opacity. For commercial construction, the two most common thicknesses are 1/4 inch (6 mm) monolithic and 1 inch (25 mm) insulating glass. Presently, 1/4 inch curved glass is typically used only in spandrel areas, while insulating glass is used for the rest of the building (sometimes spandrel glass is specified as insulating glass as well). The 1 inch insulation glass is typically made up of two 1/4-inch lites of glass with a 1/2 inch (12 mm) airspace. The air inside is usually atmospheric air, but some inert gases, such as argon, may be used to offer better thermal transmittance values. In residential construction, thicknesses commonly used are 1/8 inch (3 mm) monolithic and 5/8 inch (16 mm) insulating glass. Larger thicknesses are typically employed for buildings or areas with higher thermal, relative humidity, or sound transmission requirements, such as laboratory areas or recording studios. A bent glass curtain wall may be used which is transparent, translucent, or opaque, or in varying degrees thereof. Transparent curved glass usually refers to vision glass in a curtain wall. Spandrel or vision glass may also contain translucent curved glass, which could be for security or aesthetic purposes. Opaque curved glass is used in areas to hide a column or spandrel beam or shear wall behind the bent glass curtain wall. Another method of hiding spandrel areas is through shadow box construction (providing a dark enclosed space behind the transparent curved, bent translucent glass). Shadow box construction creates a perception of depth behind the bent glass curtain wall that is sometimes desired.