Skyscraper SPF: Spray Foam Insulation at
One World Trade Center

By: Emily Knight
 

One of the proudest moments for any contractor is standing back to survey finished work. Jacob Kloc of Airseal Insulation Systems was doing just that as he explained how he had applied spray polyurethane foam (SPF) insulation to help build One World Trade Center, which is currently under construction in New York City.

“I’m driving by it now, and it’s still holding up great,” he said of the insulation he applied to a form used for pouring the building’s concrete. Like any busy contractor, he had only a moment to savor a job well done before moving on to inspect another job site.

Even though he’s on to the next project, the SPF that Kloc’s team applied will continue to be a critical part of the construction of One World Trade Center (formerly known as Freedom Tower) for the next two years.

All the concrete for the core shaft of the building will be poured into the form that Airseal insulated. The structure, which is a 24-inch-thick steel wall composed of a series of cells, supports and insulates the concrete while it cures. As a mold-like support used to prevent cracking in the concrete, the form will be moved around each level that will make up the core of the building, from foundation to roof.

“It wasn’t the biggest job, but it was very important for the rest of the construction,” said Kloc.


Unusual Undertaking

Construction of One World Trade Center began in 2006. When completed, it will be the centerpiece of the rebuilt World Trade Center site and the New York City skyline. Its final planned height of 1,776 feet — chosen for the year of the signing of the Declaration of Independence — will include approximately 1,300 feet of concrete core. This core was contracted to Collavino Construction, and according to the Port Authority of New York and New Jersey, it will be one of the strongest and safest in any building in New York. 
Airseal’s involvement with the One World Trade Center construction began when they heard that Collavino needed a spray foam specialist to insulate the steel form. Airseal submitted a bid to apply SPF to the 40,000 square feet of the form’s vertical substrate.

One World Trade Center will be an important center for business, tourism, and government, so its construction couldn’t be delayed. Collavino needed the SPF installed in a tight time frame in sub-freezing weather. They were entrusting a potential subcontractor with the success of their concrete; if the insulation failed, the concrete wouldn’t cure properly, and weeks of construction time and millions of dollars would be lost. “Ultimately, we were awarded the bid because we had the know-how for the conditions,” said Kloc.

Winning the bid for the job was just the beginning of a long planning process before any work could begin. The construction of the One World Trade Center tower is a massive undertaking involving multiple contractors for different types of work, all being coordinated by the Port Authority of N.Y. and N.J. and Tishman Construction Corporation. Every subcontractor contributing to the construction has to go through a lengthy process of approval with the Port Authority and Tishman.

"In all, we spent about 40 hours in meetings with different parties, getting approved for the job," said Kloc. Because the application of SPF was not originally part of the project plan that Collavino submitted for the concrete, Airseal was required to present their own detailed proposal to the Port Authority, including a timeline, a safety plan, and a schedule that fit around the work of roughly 2,000 other crewmembers on the One World Trade Center site.

"We had to do most of our work on Sundays because that was the only day we could bring in a truck. On weekdays, there was a crane in the spot where we parked the truck," Kloc noted. This bureaucratic juggling act was nearly as impressive as applying SPF while suspended from scaffolding in a New York winter!


SPF Seals the Deal

Part of Airseal's winning plan was their choice of product. They selected Demilec's HeatLok Soy — a two-component, closed-cell SPF that could withstand the extreme temperature and humidity fluctuations of an outdoor job.  Temperatures were in the low 20s, but Heatlok Soy cures down to 14 degrees Fahrenheit, so weather posed no problems for Kloc and his team.

"The insulation was to make sure the concrete cured properly,” Kloc explained. “The concrete is hot going in, about 160 degrees, and because it's so cold outside, the outer edge would cure faster than the middle without insulation." That meant that the product would have to withstand repeated heating and cooling during its use.  Fortunately, this rigid foam will allow contraction and expansion of the steel substrate.

In addition to its durability, Heatlok Soy also boasts green credentials. According to Demilec, the plastic component is made with recycled polyurethane, and the blowing agent is composed of soy oils. It also emits no volatile organic compounds and does not deplete the ozone layer, making it the insulation of choice for several LEED-certified buildings like One World Trade Center.

Re-Building Memories


Kloc and a crew of 15 men completed the insulation application over four weekends.  The substrate, a steel structure used to form the concrete foundation and core, needed minimal preparation since it was built on site and ready for the Airseal crew.  The form was already in place at the foundation level and couldn’t be moved, so the crew had to work on scaffolding in the foundation hole, 75 feet below street level.

“Getting 250 feet of hose into the hole was a challenge in itself,” said Kloc. The hose had to be suspended and secured before application could begin. The spray crew staged in the hole, and then coordinated with a street level crew who operated the Graco E-30 Reactor, which mixed the foam. The distance between the two crews made communicating and calibrating the equipment the most challenging part of the application.

Each cell in the structure wall received two inches of HeatLok Soy applied in three passes with a Probler gun.  “The foam applied beautifully,” said Kloc. “It cures very well, and adheres evenly,” he explained, thanks to its high viscosity and fast gel time. This was especially important because the crew had limited time on site and no time to correct a failed application.

Since the crew was working at elevation, safety was a very real concern. Harnesses were used by all crewmembers working on the scaffolding, who tied off according to Occupational Safety and Health Administration (OSHA) guidelines.  Even though the materials used tested below permissible exposure limits, the crew used 3M respirators as an extra precaution. Tyvek suits and hardhats were also required on the busy job site at all times. Another major component of the safety plan was being aware of the other construction at the site, and carefully observing boundaries and staging zones for other work happening simultaneously.

In all, the crew covered 40,000 square feet of substrate in about 60 hours. Collavino Construction continues to build up the concrete, level by level, using the insulated form.  The Port Authority announced in February that the foundation and 35 feet of concrete above street level have been completed, thanks in part to Airseal’s work.

“Most jobs we do are interiors, and this was a really different challenge,” Kloc explained. Even though his part of One World Trade Center is done, Kloc is proud to say he’s worked on a building that will become a new national icon.

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