Energy Efficiency Measures Mitigate Pentagon Damages

February 1, 2002

Photo of DOD's Bob Billak and Lee Evey

The DOD's Bob Billak and Lee Evey are among Pentagon officials working on the landmark building's renovationn.

When American Airlines Flight 77 slammed into the Pentagon on September 11, 2001, it crashed directly into the renovated section of the building 5 days before its long-awaited completion. Remarkably, the capabilities of the building's new energy management control system and energy efficient windows, both implemented as part of the massive building renovation, proved invaluable for containing the effects of the attack.

Pentagon officials say that the energy management system, installed to efficiently manage the heating, cooling, and lighting systems throughout the Pentagon, allowed officials to manipulate all the building systems in the first minutes after the attack. The centralized energy management system minimized the areas of the building that had to be entered to operate equipment, reducing risks to employees.

Facility managers were able to shut down air handlers immediately, preventing personnel from entering a life-threatening situation where they could be exposed to toxic conditions. Pressurized air barriers were set up to prevent fumes from migrating into occupied areas. The air barriers kept toxins, gases, and smoke contained by creating high pressure zones at each border. Facility managers were also able to use the system to open outside air dampers and close others to prevent or minimize smoke entering the HVAC system. Such steps permitted those inside to continue with the Pentagon's mission-critical activities while dealing with the tragedy at hand.

The system was also utilized to contain smoke damage in the building. Exhaust and relief fans were used to remove residual smoke and odors rather than distributing them around the building through open plenums. Air quality was maintained by increasing the outside air volume brought in for areas upwind from the fire.

In addition to the energy management control system, the Pentagon's new windows also helped to contain damage from the attack. The windows, designed to be shatterproof and permanently closed, had been installed for security reasons and for their energy efficiency benefits. Pentagon officials reported that the new windows near the impact site remained intact after the plane struck. At the time of the crash many employees were standing in front of or close to the windows. The thick glass windows were potential lifesavers that day, whereas the older windows, in the unrenovated areas up to 200 feet away, blew out during the initial impact and explosion of jet fuel.

The capabilities of the Pentagon's energy management control system and the windows were far-reaching when the building was tragically attacked that Tuesday morning. The improvements served the safety purposes as they were intended, and greatly mitigated the destruction from the horrible event. In the months following the attack, the destroyed sections of the building have been quickly removed and the renovation of the Pentagon continues on, further improving the security and efficiency of the landmark building. Despite the tragic losses incurred, the Pentagon Renovation Program is continuing with its original scope of work. Structural rebuilding and all interior work of the destroyed section may last more than 3 years. Nevertheless, officials remain determined to meet the original schedule for completion in December 2012.

For more information, please contact Bob Billak of DOD at 703-695-7909 or