Illustrated Architecture Dictionary. .......................    Modern Style

Curtain wall

Curtain wall: In a framed building, an exterior wall having no structural function.  An exterior wall supported wholly by the structural frame of a building and carrying no loads other than its own weight and wind loads.

Unit system: A curtain wall system  consisting of preassembled  framed wall units which may be preglazed (windows) or glazed after installation.

Panel system
A curtain wall system  consisting of preformed metal, cut stone, precast concrete, or panelized brick units which may be preglazed (windows) or glazed after installation.

Spandrel panel: In a multistory building, a wall panel filling the space between the top of the window in one story and the sill of the window in the story above

Curtain walls

A curtain wall is defined as thin, usually aluminum-framed wall, containing in-fills of glass, metal panels, or thin stone.

The framing is attached to the building structure and does not carry the floor or roof loads of the building. The wind and gravity loads of the curtain wall are transferred to the building structure, typically at the floor line.

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.
- Excerpts: Nik Vigener, PE and Mark A. Brown, Building Envelope Design Guide - Curtain Walls (online May 2016)

Curtain Wall Style (1948 - 1965)


(online June 2016)

The Curtain Wall style refers to mid-20th Century buildings that use a prefabricated exterior wall sheathing system hung to their frames. The use of such technology dates back to the 1918 Hallidie Building in San Francisco, which is credited as the first building to use an all glass exterior wall system. However, it was not until post-WWII when advancements in building technology allowed these systems to become widespread.

The first major example of the style was the Equitable Savings & Loan Building in Portland, Oregon executed by architect Pietro Belluschi in 1948. As the world’s first fully enclosed air-conditioned building, this sleek 12-story structure quickly set the pattern for many post-WWII skyscrapers and small scale office buildings.

The curtain wall system is comprised of a repetitive grid of vertical extruded aluminum mullions and horizontal rails.

Panels called spandrels divide the large expanses of glass horizontally to hide the floors and ceilings. These spandrel panels can come in a variety of materials. Early spandrel panels were made of heat-strengthened opaque glass fused with colored ceramic. The Pittsburg Plate Glass Company manufactured the glass panels under the trade name “Spandrelite,” and offered eight standard colors. The Libbey-Owens-Ford Corporation sold sixteen colors options under the “Vitrolux” brand. Colors ranged from “Hunter Green” to “Cavalier Red,” to “Charcoal” and “Suntone Yellow."

Later, spandrels were available in other materials such as composite metal panels containing lightweight insulation cores, precast concrete panels, asbestos panels, thin stone veneer, and plywood panels (a material particularly popular in the Pacific Northwest).

Considered suitable for virtually any size commercial, government or institutional building, the Curtain Wall style became widespread by the early 1950s. Many post-WWII buildings of varying styles also incorporated curtain wall systems into some facades but are not considered Curtain Wall style unless the majority of the visible facades are so constructed. The modular construction method used to construct the Curtain Wall style made it economical and popular for a time. However, by the late 1960s it was being replaced with a more smooth or Slick Skin application.

Curtain walls

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.

As the curtain wall is non-structural it can be made of a lightweight material, reducing construction costs.

When glass is used as the curtain wall, a great advantage is that natural light can penetrate deeper within the building.

The curtain wall facade 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 is designed to resist air and water infiltration, sway induced by wind and seismic forces acting on the building, and its own dead load weight forces.

Curtain wall systems are typically designed with extruded aluminum members, although the first curtain walls were made of steel. The aluminum frame is typically infilled with glass, which provides an architecturally pleasing building, as well as benefits such as daylighting. Other common infills include: stone veneer, metal panels, louvres, and operable windows or vents.

Curtain walls

By definition, the curtain wall is an independent frame assembly with self sufficient components that does not brace the building structure.

Curtain wall may be comprised of multiple substrates including aluminum framing, stainless steel components, glazing, rubber gaskets, sealant, insulation and metal connections.

The vision area allows light transmittance and the spandrel areas [between windows] are designed to conceal the building floor beam structure and related mechanical elements. While the spandrel area is an opaque area, the architectural community always finds interesting ways to address the aesthetics by making the spandrel area pronounced (e.g. facade element glazing color change, material type change such as granite) or subtly blended as an all-glass facade when viewed from the exterior.

- Excerpts: Dudley McFarquhar, The Role of the Building Facade – Curtain Walls (online May 2016)

Examples from Buffalo architecture:

Photos and their arrangement 2016 Chuck LaChiusa
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