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Teich's Tech Tidbit 
February 2003
Revolving Doors: Always Open, Always Closed

Revolving door to Paris hotel (Credit - IRDA)
The revolving door is based on a simple idea.  By replacing conventional swinging doors with four equally spaced doors that rotate around a central pivot, revolving doors are never open to both the outside and the interior of a building at the same time.  If you have ever sat near the door of a restaurant or another nice warm space on a cold day (and who hasn't?), you know how cold air rushes in every time the door swings open.  If it is not only cold, but windy besides, the cold blasts can be even worse.

Revolving doors are expensive and relatively few restaurants have them.  They are common, however, in skyscrapers, where they serve several important purposes.  Their major function in a skyscraper has to do with equalization of air pressure. When a tall building is heated, the hot air rises, reducing the air pressure at ground level and on the lower floors.  Swinging doors in such buildings allow higher-pressure cold air to enter, creating their own wind and blowing around papers, hats, and anything else that is not tied down.  Revolving doors not only make the lobbies of these buildings more pleasant, they reduce energy costs by preventing cold air from entering. 

Revolving doors also serve an important architectural purpose.  According to Andrew S. Dolkart, an architectural historian at Columbia University, "Architects carefully choreograph a building's entrance. Every element is designed to create a sense of vastness," he noted.  In an article in The New York Times last year, Dolkart cited the Chrysler Building as an example of the skillful use of revolving doors.  The exterior of the building suggests that it will have a towering lobby, but in fact the lobby's ceiling is relatively low.  "When you walk from the small space in the revolving door and step into the lobby the space just seems to explode.  The lobby feels so big compared to the small space in the door that you don't even notice that the lobby isn't as big as you thought it would be.  That small space in the door is critical to creating the illusion."

Although New York City, with its profusion of skyscrapers, is generally regarded as the revolving door capital of the world, the revolving door was actually invented in Philadelphia by Theophilus Van Kannel, who patented the device in 1888.  Van Kannel, who was recognized for his invention with an award from the Franklin Institute, founded the Van Kannel Revolving Door Company, which eventually was bought out by the International Steel Company.

In today's security-conscious environment, revolving doors also have another advantage:  they can make it easier to control access to a building.  As can been seen in one of the links below, revolving doors can be outfitted with biometric devices, metal detectors, and other screening and access control mechanisms.

Finally, although it probably was not what Theophilus Van Kannel had in mind, going around and around in a revolving door can be lots of fun--especially if you're a kid.

Links:

The International Revolving Door Association.  First on its list of objectives is "to contribute and direct the development of international safety standards through interaction with various local and global regulatory authorities."  Under Q&A, the site provides brief information on safety, security, energy use, and other subjects.  There is also a rather nice gallery (source of the photo above).

International Revolving Doors of Evansville, Indiana, a direct corporate descendant of the Van Kannel Company described above, has an extensive web site with information on the history and advantages of the revolving door in addition to descriptions of its products.

"Why Install a Revolving Door?"  The AGP Group, an Australian firm has the answer: it keeps the wind out.  The company offers a wide range of revolving doors, from budget to high end.

Eastern Door Service, Inc., in New Jersey, has many types of automatic doors, and some manual ones as well.

Crane Revolving Door Company of Lake Bluff, Illinois, describes itself as "the leader in high-end revolving doors."  Its site features a photo gallery of its installations.

Safesec Corporation of Ontario, California, sells security-oriented revolving doors.  Described as "entrance control solutions," its products offer such options as biometric devices and metal detectors.  Quintron Systems, Inc., has a similar product line.  And ABACOS Automation of Lanarkshire, U.K., makes revolving doors with bulletproof glass.

Boon Edam BV of the Netherlands describes itself (in a 2008 e-mail to me) as the "acknowledged world market leader in revolving doors." It lists among its accomplishments "the world's first energy generating revolving door."

The Half-Bakery, a site that collects some strange ideas for inventions, features a "revolving doors clock."  It would have three doors, one making a full rotation in 12 hours (with an entrance-exit time of six hours), one rotating in an hour, and the third in one minute.  It seems unlikely to catch on. 

    E-mail your tidbit suggestions to ateich@aaas.org.

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