Case Studies – Temporary Climate Solutions

Restoring the Pentagon after 9/11 attack

The impact and explosion that occurred when terrorists crashed a hijacked airliner into the side of the Pentagon Building devastated a significant area on five floors of the world-renowned US military headquarters. Water damage caused by fire hoses, sprinkler systems, and shattered water lines, affected 2.5 million square feet of space adjacent to the crash area adding to the physical destruction of the event.

It was our honor to support the stabilization and recovery of the building in the aftermath of the attacks. Our primary responsibility was to dry out the spaces impacted by the water damage to reduce reconstruction costs and schedule. Our team designed and installed a temporary dehumidification system to move over three million cubic feet of air per minute through more than a mile of ductwork to accomplish the mission. This high-priority critical assignment required many teammates, partners, and pieces of equipment from across the country. It was the largest single-building project our team had worked on up to that point and one we are grateful to have been a part of.

“Polygon dried an area on five levels greater than 33 football fields, all of which was damaged by the water alone,” said Waltemire. Making a conservative estimate, Waltemire believes that Polygon saved the Pentagon more than 40 million dollars in reconstruction expenses. “Beyond the money saved, drying allowed this important space to be back in use months earlier.”


The Pentagon is designed in a circular structure of five “wedges.” Each wedge has a corner of the building at its center. The attack occurred between “Wedge 1” and “Wedge 2” with fire and water damage occurring on both sides of the crash site. At the time of the event, Wedge 1 was nearing completion of a comprehensive, $258 million renovation project.  

“Millions of gallons of water flowed throughout the building after the attack,” said Larry Waltemire, Polygon’s Regional Manager in Washington, DC. In some places, the water was 18 inches deep.

On the ground level, the exterior buildings share a common floor. On the upper floors, they rise as separate towers. When the airliner hit, it penetrated the exterior wall and slid into the middle of the building. The devastated area was approximately “V” shaped, with greater destruction occurring in the outer areas.

Our team offered its services immediately after the disaster. However, Pentagon building managers could not respond because the FBI and military services had taken command of the building, prioritizing national security issues.

After security issues were addressed, we were invited by John Kirlin Construction Company, a subcontractor working with AMEC Construction on the Pentagon restoration team to tour the building and propose restoration procedures. The teams accessed the space and divided it up into Zones.

  • In “A” zones, areas nearest the crash site, the water damage was devastating, and mold was horrendous. There, mold grew well up the walls and in some cases 2 inches thick on the carpet.
  • In “B” zones, water damage was very heavy, and mold growth had become substantial.
  • In “C” zone, areas furthest from the blast, ensured only some water damage and minor mold growth.

“Despite extensive water damage and the delays caused by the unprecedented security procedures,” we were confident we could reduce reconstruction time significantly and save the majority of the newly remodeled areas,” recalls Waltemire.


Polygon proposed immediate action on Zones B and C. The team was clear that they would prioritize Zone C but also believed they could save at least 60% of the sheetrock, virtually all the new structural and mechanical materials, in Zone B. Treating both spaces would reduce overall mold growth and save millions in new construction. “We could also have the areas dry enough for use in less than one week,” recalled Waltermire. “[Zone B] was to be a salvage operation, but the advantages weighed heavily in favor of drying over ripping it all out.”

After Polygon’s presentation, Project Managers across the country immediately mobilized equipment. “It was no time to pull punches,” said Rob Sullivan, Polygon’s Northeast Operations Manager. The country was in a crisis. If we got the contract, we wanted no delays.”

The next day Pentagon managers authorized Polygon to start work. “Pentagon officials were most impressed when Polygon equipment began arriving at the Pentagon just hours later,” said Sullivan. “We had electrical generators and Polygon’s dehumidifiers at the site the same day and began assembling our drying system immediately.”

The system solution had two major components: dehumidifiers and air scrubbers.

The dehumidifiers were hoisted onto the damaged floors through bomb-resistant windows which were specially removed to expedite the process. Once positioned and powered up, the dehumidifiers drew in humid outside air, dried it to an extremely dry condition, and pumped the air into the damaged areas. A network of flexible ducts distributed the air to all parts of the “C” and “B” areas.

Simultaneously, the air scrubbers filtered the air for dust and mold spores kicked up by restoration activities. This prevented the migration of mold and mildew spores to non-affected areas.

“The Polygon team was very effective,” said David Rosner, Project Manager, John J. Kirlin, Inc. Their equipment began showing up within hours. With all they had to do, they were never stressed or overwhelmed, and it was a big job! They methodically set up and acted swiftly to new requests and changes. The company proved very easy to work with!”

When Polygon was awarded the ‘C’ and ‘B’ phases of the project, it seemed unlikely that drying ‘A’ zones was an option since an early decision was made to put front loaders on each floor and bulldoze everything inside. As things progressed, officials reconsidered and asked Polygon to access the space. Mold growth was so advanced our team had to wear respirators to enter. Although terribly affected, we felt we could dry and stabilize the space faster and more economically than they could demolish it and rebuild it.  Officials agreed and modified their plans awarding Polygon the “A” zones to dry, as well.


Rapid Response

When our country was hit by disaster, Polygon offered its services to help in any way possible.

Repair over Replace

Drying the spaces meant the team could save many of the materials used in renovation reducing rebuild costs later in the process.

Expedited Schedule

Drying also meant the facility was on a faster track to being available for use. Demolition and total rebuild would not only have cost more but also took much longer.


1 year later, Polygon team members received honorable recognition for their efforts in restoring the Pentagon.

In 2001, 189 people were lost at the Pentagon on 9/11 and the building suffered tremendous damage.