From Medieval to Modern Times: Curtain Walls Serve Multiple Purposes

Unless you're an architect or a structural engineer, the term "curtain wall" may be an unfamiliar one to you. It is not an interior design feature. A curtain wall is a type of façade often found on commercial and office buildings.

A curtain wall does not carry any dead load from the building other than its own. In other words, a curtain wall does not carry any roof or floor loads. Instead, it transfers loads to the main structure of the building through connections at the buildings different floors or columns. Essentially, it is like covering the front of a building with a "curtain" of aluminum and glass.

While aluminum and glass are fairly modern materials, curtain walls are not a modern invention. They have actually been around for centuries. The earliest of these structures were made of stone. They were most often built to surround and protect castles. These curtain walls were typically connected by a series of several towers. The towers provided defensive strength, and were also used as lookouts. The towers were the weight-bearing structures of the walls. Some medieval curtain walls, or at least remnants of them, still stand in European countries.

You won't find many curtain walls made of stone today. Modern builders construct them out of aluminum and glass. Aluminum is a natural choice for contemporary curtain walls because of its excellent strength-to-weight ratio. It also weathers well, in part because it oxidizes naturally when exposed to air, creating an extra barrier of protection against weather. Aluminum is less brittle than heavier metals like steel, and is pliable enough to be molded and bent into unique and customized configurations.

Curtain walls are constructed by fashioning aluminum into a large grid-like frame. The spaces in the frame are infilled with glass. While glass is the most common material used, it's not the only one. Metal panels, louvers and stone veneer can also be used. The structure is attached to the main building at each floor and at its corners.

Glass and aluminum tend to be the materials of choice for commercial buildings when it comes to curtain walls. Using glass is advantageous because of the natural light that it provides. Buildings with these glass facades often save money on electricity because the need to use interior lighting during the daytime is reduced significantly. Plus, glass is aesthetically pleasing, creating a modern, open-air look both inside and outside the building.

Curtain walls are advantageous for other reasons too. They are resistant to air and water infiltration and thus decay more slowly than other types of building materials. They also resist forces of nature on the building, like high winds earthquakes.

In addition to the natural oxidation process which protects the aluminum in curtain walls, another coating is usually added. The two main options for coating include anodization and electronically-sprayed polyester powder. Both of these methods enhance the weatherproofing of the aluminum and can be color-matched.

Modern curtain walls have advanced in both style and materials from their medieval stone ancestors. Today's structures can be custom-manufactured to fit any size and style of building. Aluminum colors can also be customized to match. Tinted or clear glass may be used as infill. The result is an overall look and feel that can be tailored to suit every cityscape, business park or individual developer or owner's taste.

Jenny Schweyer is a freelance writer from the Pacific Northwest.

Steiner Doors: Manufacturer of custom architectural curtain walls and aluminum doors.

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