If you’ve ever been to a major metropolis, you’ll notice that most large buildings have double or revolving doors. Since only large cities have unusually tall buildings, they are one of the only places you will see these types of doors. Although it may seem as though revolving doors in New York buildings are there to improve traffic flow, they also serve a structural purpose.
You may have found that a windy day can make a door harder to open or close. You’re fighting against the pressure because of sudden compression inside the building as you open the door. In some cases, doors get sucked open as if by magic when a building doesn’t have an adequate seal. The same principle applies to a skyscraper but on a much grander scale.
Don’t Break the Seal
The pressure never changes when a revolving door opens and closes because the seal never breaks. The action of multiple doors spinning prevents air from escaping or entering as someone moves through the space. Maintaining equilibrium is essential in large structures, and few buildings are quite so large as those found in Manhattan.
The next time you walk through a revolving door, you can thank the installers for making it much easier to enter and exit the building.