A sky lobby is an intermediate interchange floor in a skyscraper
where people can change from an express elevator
that stops only at the sky lobby to a local elevator which stops at every floor within a segment of the building. When designing very tall (supertall) buildings, supplying enough elevators is a problem – travellers wanting to reach a specific higher floor may conceivably have to stop at a very large number of other floors on the way up to let other passengers off and on. This increases travel time, and indirectly requires many more elevator shafts to still allow acceptable travel times – thus reducing effective floor space on each floor for ''all'' levels. The other main technique to increase usage without adding more elevator shafts is double-deck elevator
Early uses of the sky lobby include the original Twin Towers of the World Trade Center
and 875 North Michigan Avenue
One World Trade Center (Manhattan)
One World Trade Center
is the tallest skyscraper in New York City
. Like the original World Trade Center buildings it replaced, the new building has a sky lobby to balance the loads and convenience of individuals ascending via the elevators. The sky lobby is located on the 64th floor, and serves all passengers wishing to travel from the ground floor lobby to higher floors. Each set of approximately 5-6 stories is served by one bank of elevators. The elevators from the ground floor to the 64th floor sky lobby are the fastest in the Western Hemisphere, traveling at the same speed as the elevators used for the nonstop One World Observatory
service, which transports guests to the 100th floor in under one minute.
875 North Michigan Avenue (Chicago)
The John Hancock Center
's sky lobby on the 44th floor serves only the residential portion of the building that occupies 48 floors (floors 45–92). Three express elevators run from the residential lobby on the ground floor to the 44th floor, with all three of the elevators stopping at one of the parking garage levels. At floor 44, residents transfer to two banks of three elevators. One bank serves 21 floors (floors 45–65) and the other serves 28 floors (floors 65–92). Although all six elevators stop at floor 65, this floor is roughly the same layout as the residential floors immediately above and below it. It is not a sky lobby because residents can also board elevators to higher floors at floor 44.
The tower's 44th floor sky lobby includes a pool, gym, dry cleaner, convenience store, about 700 mailboxes, two "party" rooms, a sitting area overlooking Lake Michigan, a small library, a refuse room (with trash chutes emptying here), offices for the managers of the residential condominium
, and a polling station for residents during elections.
Floors above 92 are serviced by direct passenger elevators from the ground floor, and by two freight elevators that serve 55 floors (floors 44 to 98).
Buildings with sky lobbies
thumb|The former World Trade Center
, designed by Minoru Yamasaki
, used sky lobbies, located on the 44th and 78th floors of each tower.
thumb|The Nina Tower