Session S7 Report


Skyscraper Cities: The Logic of Vertical Density Carol Willis, Director, Skyscraper Museum, New York Decarbonization of Our Central Cities Adrian Smith, Partner, Adrian Smith + Gordon Gill Architecture, Chicago The Future of Urban Tall in a World of Uncertain Economics Sandy Diehl, Richard Hanson, Adrian Smith, Carol Willis Session Chair: Janice Tuchman, Editor-in-Chief, ENR / McGraw Hill, New York .

This session looked at tall buildings more generally in the context of the larger city. As the world’s populations continue to urbanize, the tall building will play an important role in housing these increased urban populations in a healthy, socially-responsible and sustainable way.

	.	Carol Willis coined the term “Vertical Density” to describe the positive way through which tall buildings create dense urban space. Willis introduced the topic through comparison of cities such as New York City, Hong Kong, Cairo, Mumbai, Delhi, Sao Paulo, Tokyo, London, Mexico City, Moscow and Shanghai. By comparing population to area, i.e., density, Willis explains that even though cities may show the same statistical density, the ways in which density is expressed and experienced in these cities can be quite different. Willis advocates Manhattan as an area where density leads to an attractive way of life in which buildings and space cooperate to create a vital urban space. But she was careful to point out that she in no way advocated that the population density of Manhattan (70,000 people a square mile) was appropriate everywhere.
Carol Willis, Skyscraper Museum

Adrian Smith, Adrian Smith + Gordon Gill Architecture		Adrian Smith began by presenting his firm’s plans for the US$350 million retrofit of the Willis Tower in Chicago, which is aiming to significantly reduce its energy use. One of the most basic yet beneficial improvements is re-glazing the building’s 16,000 single-pane windows. This will create effective day-lighting and ultimately 40% less lighting energy consumption. The plan also includes a new hotel tower to be built on the existing plaza. The work done on the Willis project sparked Smith’s firm to also take this subject to the larger scale of Chicago’s downtown, for which he studied the potential of reducing carbon emissions through analyzing the buildings in the study area including their use, size, current carbon emission, energy use, age, and other factors. The study revealed the profound scale that reducing carbon emissions for a major urban area requires. In order for Chicago to meet the often cited “2030 Challenge” of reducing its carbon emissions by 80% it would need to reduce its annual carbon output by 3.12 million metric tons. To achieve this by clean energy alone would require 90,000 acres of land to house 600 large wind turbines at a cost of US$2.7 billion, or 40,000 acres of photovoltaics at a cost of US$24 billion. Smith’s study found that if they applied the same retrofit techniques to all Chicago downtown area buildings they could achieve a 35% reduction (at an estimated cost of about US$6 billion).

The Future of Urban Tall discussion panel

The “sustainable future of urban tall” notion was further debated in a panel discussion moderated by the session chair, Janice Tuchman, becoming a lively debate amongst the panelists and several audience participants. Some key points raised during the panel included Richard Hanson’s argument that a far greater impact would be had by getting people to move into the city and lose their cars than by imposing costly “green” regulations on building developers. And Sandy Diehl raised the point that while it is important to have big problem statements to work towards (as had just been presented by Smith) we cannot lose sight of the reality that cost is a major issue. There is a lot of work that can be done right now on a smaller scale with existing technologies and relatively quick paybacks, while we continue to work on the bigger picture.