Photo © Hannah Thomson
Sara Hart: The Skyscraper Museum mounts exhibitions on the history and the future of high-rise buildings. What can we learn from history about the next generation of tall (and supertall) towers?
Carol Willis: Well, many people focus only on height in vertical feet, and they assume that skyscrapers are growing ever larger. But tall and big are not the same thing. Bigness is about overall scale—it's a measure of how much space a building encloses. Commercial architecture is a business, and developers create space to rent it and maximize a revenue stream.
SH: What, then, is the world's biggest building?
CW: We did an exhibition called Big Buildings back in 1999, before Burj Khalifa (known then as Burj Dubai) was a glimmer in the sheik's eye, that analyzed this question. We found that the skyscrapers of the mid-1960s and early 1970s were the biggest ever built. Each of the Twin Towers of the original World Trade Center had 4.5 million square feet of office space. Similarly, the contemporary Willis Tower (formerly the Sears Tower) contains 4 million square feet. Today the Sears Tower has been exceeded in height by five to seven buildings (depending on how one defines which vertical bit is being measured), and at 2,717 feet, the Burj Khalifa soars around twice its height of 1,450 feet. But Burj Khalifa tapers as it rises, and so it contains only 3.3 million square feet. In all the new supertall construction around the world today, there's not one tower that has 4 million square feet of space in it. I don't think we will ever see those giants of the 1960s and '70s again. On the other hand, I do think vertical density is enormously important to an efficient and sustainable urban future. But we don't need to focus on stretching the height. The focus should be on the benefits we can generate with high-rise development, which are related to creating great mass transit.
SH: There’s a lot of buzz about Sky City One in Changsha, China, which will be the world’s tallest prefabricated tower, if completed. All of the developer’s statements have invited skepticism, but the media can’t stop hyping it. What do you think about the claims regarding the reduction of embodied energy by building modules in a factory?
CW: I’m very skeptical about that project, not because of its height but, again, because of its overall size. The space inside the monumental city-pyramid they envision is around 10 million square feet. That is an unprecedented amount of space. Regarding the issue of prefabrication—I don’t think that really matters one way or the other in terms of sustainability. Skyscrapers are a long-term investment. The Woolworth Building is 100 this year; the Empire State Building is 82, and its owners just finished a major facelift and full-body rejuvenation. Both are still beloved buildings and are producing revenue, so I don’t buy the argument about reducing either construction time or embodied energy by using prefab units. You invest in the embodied energy one time, and then you live off it for a century. Creating quality buildings is the best way to ensure the long-term value of the investment in real estate.
SH: The New York City Department of City Planningis proposing rezoning (or “upzoning”) of East Midtown, a 73-block area surrounding Grand Central Terminal. Why did you testify before the City Council in support of the proposal?
CW: In my statement, I emphasized that density is vitality, and the Grand Central district can easily support greater density due to its extraordinary mass-transit infrastructure. Over the past century, the transportation nexus of Grand Central has afforded East Midtown advantages that have created an area of unparalleled prestige and accessibility for all sorts of workers and consumers.
Within this decade, the system will be enormously enhanced by the investment in the Long Island Rail Road East Side Access. The Commission’s proposal for moderate upzoning and air-rights transfers will incentivize reinvestment in older buildings of the 1960s and ’70s that are egregiously energy inefficient and enormously expensive to modernize. Then, the East Midtown market can continue to compete effectively with areas of new construction.