The revolving door might be annoying to use, but it has a lot of energy advantages over the swinging door.

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The next time someone quips, "nothing is impossible," ask if they've ever tried to slam a revolving door.

A revolving door consists of multiple panels that rotate inside a cylindrical rotunda -- and not one of these fixed panels can be slammed shut. While this might not be great for making a point during a heated discussion, a revolving door does offer a number of benefits.

Although a revolving door isn't airtight, it does prevent significant amounts of noise, snow, rain and air pollution from entering a building, especially if it borders a busy street. As we know, energy is lost every time a door is opened in an air-conditioned or heated building. With a revolving door, at least one panel is almost sealing the building and reducing the amount of energy leaving it.

In fact, a 2006 study conducted by MIT graduate students tracked the usage of revolving doors versus swinging doors (the traditional kind of door) at one campus building. The swinging door allowed eight times more air to pass through than the revolving door. The students calculated that if everyone entering or exiting the building used the revolving doors, taking into account local weather conditions, the energy savings would be around 75,000 kilowatt-hours per year. This would decrease the amount of energy normally used to heat or cool the building, and would prevent nearly 15 tons (13.6 metric tons) of carbon dioxide from being released into the atmosphere [source: Leibenluft].

A revolving door can ease interior and exterior air pressure differences, too. If you've ever tried with difficulty to pull open a swinging door to enter the lobby of a skyscraper, then you've probably experienced this change in pressure. A revolving door, however, allows air to exit and enter the building at a nearly constant rate, eliminating drastic pressure changes [source: National Inventors Hall of Fame].