A change to the design of a needle that will sit atop One World Trade Center is raising questions over whether the building will still be the nation's tallest when completed.
The 408-foot needle will no longer be enclosed in a fiberglass-and-steel enclosure called a radome, a feature that was recently removed from the design because the building's developer says it would be impossible to properly maintain or repair it.
Without the enclosure, it's unclear whether the needle is an antenna or a spire -- a crucial distinction in terms of measuring the building's height.
Without the spire, One World Trade Center would be shorter than the Willis Tower in Chicago, currently the tallest building in the United States at 1,451 feet, not including its own antennas.
Last week, One World Trade became New York City's tallest building as workers erected steel columns that were just high enough to rise above the Empire State Building's observation deck. The building is meant to replace the Twin Towers, destroyed in the Sept. 11, 2011, terror attacks.
In order to repair or replace a broken panel on the needle's proposed enclosure, a climber would have had to scale the spire, attach a cable to the top, lower the cable about 2,000 feet down, and then use it to hoist a 2,000-pound piece of fiberglass back to the top, said Jordan Barowitz, a spokesman for Douglas Durst, the building's developer.
"This is the stuff of 'Mission: Impossible,' not skyscraper construction," Barowitz said.
The tower's architects at Skidmore Owings & Merrill Llp did not respond to a request for comment Thursday.
Designs call for the tower's roof to stand at 1,368 feet -- the same height as the north tower of the original World Trade Center. With the needle, the building's total height will be a symbolic 1,776 feet.
Experts and architects have long disagreed about how to measure the height of skyscrapers that have masts, spires and antennas.
The Council on Tall Buildings and Urban Habitat, a Chicago-based organization considered an authority on such records, says antennas do not count when determining building height. An antenna, the group says, is something simply added to the top of a tower that can be removed. By contrast, a spire is part of the building's architectural design.