LONDON – The skyscrapers of the post-Sept.-11 era will likely be significantly different structural animals, most industry analysts concur. Revamped building regulations and design codes, plus requirements for more, and wider, fire escapes will, for example, probably be fixed parts of the post-9/11 equation for high-rise construction.
        But the hot debate sparked by Sept. 11 is not only over how skyscrapers should be built, but whether they should be built at all. The debate over the World Trade Center site's future takes in part of the divergent points of view. Passionately advocated options have ranged from leaving the site empty, to building smaller 50-story structures, to constructing skyscrapers that match the soaring heights once attained by the WTC's twin towers. Still other voices back a hybrid, combining a smaller memorial with one of the two other options.
        Now, from across the Atlantic comes yet another perspective: Skyscrapers, says a newly released study, are not only "an inevitable building form," they're also "more environmentally sustainable" than smaller buildings.

A key element in the Commerzbank tower's environmental friendliness is its huge central atrium (pictured). The atrium reaches from the ground floor to the top of the building, which stands 981 feet (299 meters) tall. The atrium's inner ring includes nine "sky gardens," each standing four stories tall. Photo: Foster and Partners, London

        Commissioned by the Corporation of London (www.cityoflondon.gov.uk), the study - titled "Tall Buildings and Sustainability" - was conducted by Faber Maunsell (www.fabermaunsell.com), one of the UK's largest engineering consultancies.
        This report, however, doesn't reach for the Jumbotron-scale rethinking that's now a major thrust for many of the most prominent U.S. construction associations. Instead, the report is part of an initiative to plot London's future growth. Narrow focus notwithstanding, the London study adds some different food for thought to the current contretemps over skyscrapers' future.
        "The Corporation [of London] needs to ensure that demand for office space can be met within the Square Mile (the London area in which much of the city's financial industry is located)," says the "Tall Buildings and Sustainability" report. "In this context, tall office buildings are becoming increasingly necessary as a result of the efficient use that they make of the limited land available."
        The bulk of existing skyscrapers, however, rate a firm thumbs-down from the study.
        "The primary design concern for many tall buildings is their operational efficiency rather than their environmental impact," notes the Corporation of London/Faber Maunsell report. "A new balance needs to be struck between these two factors."

Report Backs 'Bioclimatic Skyscrapers'

That balance between efficiency and environmental impact, however, already exists, says the study, in what the authors call "bioclimatic skyscrapers." One bioclimatic skyscraper particularly "stands out," the study asserts: the Commerzbank tower in Frankfurt, Europe's tallest building, which was designed by Sir Norman Foster (www.fosterandpartners.com) and completed in 1997.
        (The 1,016-foot/310-meter London Bridge Tower, which has already been approved by London planners, will surpass Commerzbank to claim the title of Europe's tallest structure. The London Bridge Tower project was one of the developments that spurred the Corporation of London to commission its study.)
        Standing 981 feet (299 meters) tall, Germany's 56-floor Commerzbank building is the antithesis of the sealed, central-climate-controlled model that typifies most American high-rises. Every office in the Frankfurt facility receives natural daylight and ventilation, and each has windows that can be manually opened. In compliance with German building code, all employee workstations in the Commerzbank tower are located within 24.75 feet (7.5 meters) of a window.

"This report shows that tall buildings are not a hindrance to sustainability - quite the opposite," said Judith Mayhew (pictured), chairwoman of the Corporation of London's policy and resources committee.

        The triangular building's "petal-and-stem" design is a key element in the facility's friendliness to both employees and the environment, the study contends. The structure's three petals contain the building's offices. Those three petals flare out from a central atrium, which stretches from the ground floor to the top of the building, providing a natural ventilation tower. The atrium's inner ring features nine huge "sky gardens," each standing four stories tall.
        "This report shows that tall buildings are not a hindrance to sustainability - quite the opposite," said Judith Mayhew, chairwoman of the Corporation of London's policy and resources committee.

'Clustering Can Improve Sustainability'

The "Tall Buildings" report (which can be downloaded in its entirety from the Corporation of London's Web site) puts particular emphasis on energy consumption.
        "Almost three quarters of London's energy consumption is in buildings," the study notes. "Whilst energy use is currently a relatively minor financial cost [for office-space occupants], it is associated with major environmental costs, particularly climate change."
        The study's recommendations for London's tall buildings include using "passive solar heat and [the] thermal mass of the building, high insulation levels, natural daylight and wind power." "As this report makes clear," Mayhew commented, "putting sustainability at the heart of the design, construction and operation of buildings makes economic and business sense."
        The report also advocates density in the location of business operations, another part of ongoing U.S. post-9/11 debate. Such corporate concentrations are a central tenet in promoting London's sustainability, asserts "Tall Buildings and Sustainability."
        "Clustering already provides numerous business advantages but it can also improve sustainability in areas such as transportation, energy efficiency and land use," Mayhew said.

U.S. High-Rise Debate Takes Different Direction

Meanwhile, the dialogue on the future of U.S. skyscrapers continues to take a different focus - one that could take years to fully sort out.
        "Help me understand why it's a good idea to build more skyscrapers that are targets for terrorists?" Rep. Roscoe Bartlett (R-Md.) asked during congressional hearings on building safety that were held in Washington in March.
        Replied Rep. Joseph Crowley (D-N.Y.), "We can't simply flatten Manhattan."
        Building a 100-percent safe skyscraper, however, may well be unattainable, CTL Engineering Senior Vice President Gene Corley testified during the hearings.
        "Because there is no limit to the destructive forces which terrorists can bring to bear against our built infrastructure, it is impossible to design a building to withstand such an attack," Corley said.
        Corley who served as the first-phase chairman of the national building assessment team, which includes the American Society of Civil Engineers, the Federal Emergency Management Agency and the National Institute of Standards and Technology. That team on May 1 released a preliminary report. But the full report, including building-safety recommendations, may take two years to complete, team members indicated.
        Legislators at the March hearings urged quicker action.
        "There are buildings going up right now that can use the benefit of the knowledge that is coming out," said Rep. Felix Grucci (R-N.Y).