Ten years ago today, Chicago developer J. Paul Beitler โ€” who once aspired to build the world's tallest building โ€” told The Chicago Tribune that governments would cease to approve plans for skyscrapers, for fear that they would become "magnets for future terrorism."

The events of September 11th forever changed the way we approach architecture and design. In the ten years following September 11th, "security at any cost" became the mantra of many.


Architects have raised safety in tower design to unprecedented heights โ€” but they've also managed to do so in aesthetically and environmentally conscious ways. Contrary to Beitler's prediction, skyscrapers continue to pop up worldwide, and what will soon become the tallest tower in the United States is rising higher into NYC's skyline every day; when it is complete, One World Trade Center will not only be one of the safest skyscrapers in the world, it will also be one of the most environmentally sustainable. The design of One WTC represents not just how 9/11 changed architecture, but how it changed architecture for the better.

Here are 10 ways that One WTC embodies that change.

10) Stairs
The emergency stairs in One World Trade Center will be significantly wider than those called for by building standards in New York, and will include additional exit locations. The extra space will allow for evacuations to be carried out more efficiently in the event of an emergency. WTC architects have also designed a set of stairwells exclusively for use by firefighters and rescue personnel.


9) Air supply
Air circulating through the tower will be drawn from the outside using machines that pull in air from the top of the tower, where it is cleaner. Inside emergency stair wells, the air will be kept at a higher pressure than the outside air to help keep them clear of smoke in the event of a fire.

8) Biological and chemical air filters
The ventilation system for each floor of 1 WTC will be outfitted with a dual-filtration system that will clear the air, not just of particulates in the natural-air supplied from outside, but of chemical and airborne threats as well.


7) Reinforced foundations
The first 19 stories of 1 WTC are built like a bunker, fortified with a 185-foot, reinforced concrete base to protect the structure from the force of a car bomb. (Image via NYTimes)

6) Subtle security
Immediately following 9/11, many skyscrapers around the country and around the world resorted to "militarized urbanism," erecting strong and effective security barriers at the expense of aesthetics and environmental concerns. For an example of militarized urbanism in action, look no further than the infamous Jersey barrier, (pictured here via). Following September 11, Jersey barriers were featured prominently at the base of skyscrapers across the country.


But as NY Times' Henry Fountain puts it, subtlety is beginning to creep back into security. Jersey barriers have been replaced with street furniture, plantings or other landscaping features that are aesthetically pleasing, but can still keep a car from driving into a building, for example. Ten years after 9/11, engineers are looking for new and creative ways to balance concerns over protection, aesthetics, and the environment.

5) Green cooling and irrigation systems
And in true "subtle security" fashion, One WTC is said to be "the most environmentally sustainable project of its size in the world." The tower will feature, for example, a rainwater collection and recycling scheme. The reclaimed water will be used in the tower's cooling and irrigation systems. But how is this linked to security? When air is continuously circulated from outside โ€” as it will be in 1 WTC โ€” it must be continuously cooled or heated as well, typically at considerable expense; using reclaimed water in the cooling process accounts for both environmental and safety concerns.

4) Elimination of accelerants as heating elements
The tower will also forego the use of oil and natural gasโ€”based heating elements (which are also accelerants that can fuel and quicken the spread of fire) wherever possible; the building will instead by heated by steam as part of a 4.5 million watt building fuel cell (waste steam will also be used to generate electricity).


3) Location, location, location
One of the biggest new security measures doesn't involve fancy filtration systems or novel architectural ideas โ€” it simply increases the distance of One WTC from the street. The new tower will stand at an average of 90 feet from all surrounding streets (the previous towers were positioned an average of 25 feet from the street); at its closest point, One WTC will be 65 feet away from West Street.

2) Glass
Another good example of subtlety in security is the extensive use of glass in the new World Trade Center. The modern architectural era is all about glass, light, and openness โ€” qualities that one does not typically associate with security and strength. (Photo via)


One WTC, however, manages to achieve the light and airy qualities of a glass box, while maintaining the strength and security of a fortress by being what architecture professor Garth Rockcastle refers to as "a concrete fortress in glass clothing." The implementation of blast-resistant glass and plastics at One WTC will protect the tower and reduce its operating costs, all while providing a sense of openness.

1) Concrete
As we mentioned above, concrete fortifies the base of One WTC, protecting it from bombs and impacts. But the core of 1 WTC โ€” what its architect, David Childs, calls "the center spine of the building" โ€” is encased in several feet of a new formulation of concrete that is roughly three times as strong as typical concrete; all stairwells are reinforced with 3-foot-thick concrete walls; and concrete will be used to encase and protect everything from sprinkler systems, to emergency risers, to communication systems.

Additional Reading
Renew NYC Freedom Tower Fact Sheet
"The Age of the Eco-Citadel"
"How Has Skyscraper Design Changed Since 9/11?"
"Did 9/11 Change The Way We Build?"


Top image via
Additional reporting by Keith Veronese