Tapered EPS Approach Protects Airline Facility’s Roof

When a 200,000 square meter warehouse was converted into an operations center for airport networks, the roof system had to be completely redesigned. Photos: Insulfoam

Chicago O’Hare International Airport, the sixth largest airport in the world by total number of passengers, accommodated 84 million passengers and 900,000 incoming and outgoing flights in 2019. Of course, almost every domestic commercial airline is represented at the international transportation hub. To ensure that passengers arrive at their final destination safely and on time, each airline is supported by a Network Operation Center (NOC). From this external location, hundreds of highly qualified employees coordinate travel logistics and monitor daily flight activities.

When designing a world class NOC facility, a properly insulated roof system plays an essential role in optimizing operational efficiency and ensuring long-term protection. When a major commercial airline near O’Hare bought 200,000 square feet of storage space to house their new NOC, the project designers turned their attention to the roof. During the initial test, the existing roof system was rated as sub-par and the NOC project designers were selected for a full overhaul.

A creative roof solution

The project’s roofing company, Olsson Roofing, faced with sourcing a superior insulation material for the renovation, selected Insulfoam’s Conical Expanded Polystyrene (EPS). Tapered EPS meets the requirements of the International Building Code (IBC) for both new construction and roofing applications while maintaining constant thermal output and long-term moisture resistance.

NOC’s project designers turned to this rigid foam insulation as a logical and inexpensive means of increasing the spacing of the low-slope structure. A positive slope reduces the stress on the roofing membrane by eliminating the risk of stagnant water, which is a serious threat to the integrity of the building system. Without adequate drainage, builders can suffer costly repairs on the street or premature roof failure. The conical EPS approach enables NOC project designers to proactively avoid these problems and extend the life of the roof system.

Moisture resistance

The crews from Olsson Roofing installed flat and tapered EPS insulation and a TPO membrane.

Long-term exposure to moisture can be extremely damaging to a roof system. While the purpose of an EPS conical approach is to keep pool water in check, moisture uptake is sometimes inevitable – especially during the Chicago winter months. For the benefit of the NOC project designers, EPS offers a high level of moisture resistance and breathability. A study by Energy Materials Testing Laboratories (EMTL) has shown that EPS installed in a well-constructed roof does not absorb significant moisture, even under conditions characteristic of prolonged, cold, and humid winters. The same amount of absorbed moisture (0.2 percent by weight on average) has little or no impact on compressive or flexural strength, and the material retains between 95 and 97 percent of its thermal efficiency. With this ingenuity, NOC project designers can ensure the roof system is ready for the harsh Chicago weather.


Because tapered EPS is available in large blocks up to 40 inches thick and can be cut to suit virtually any slope, it is possible to achieve superior thermal efficiency – high R values ​​- without the added material or Achieve labor costs normally associated with building multiple layers of insulation. Similar to installing giant puzzle pieces, the small crew hired to build the NOC was able to easily glue three layers of 4-inch EPS in combination with flat EPS over the roof terrace. The factory-cut pieces of material were installed quickly thanks to their ultra-light composition. In use, the rigid foam material kept the project on budget by lowering material costs in advance and minimizing the number of hours spent on the construction site.

The project designers at NOC were looking for a tapered EPS to not only save material and labor costs, but also to achieve stable thermal output. The EPS insulation provides R values ​​between 3.6 and 4.2 per inch. EPS with a rating of R-4 per inch can provide up to twice as much insulation as other insulation materials of the same thickness. Much to the delight of the NOC project designers, Insulfoam was able to supply the desired R-25 designation in three layers of material, thereby reducing the costs associated with building the pitch.

Additionally, third-party tests conducted in 2008 assessed the field performance of EPS after a continuous installation period of 15 years. The results showed that EPS delivers 94 percent of its stated R value after 15 years. Since the material is not degassed, the R-value remains stable over the entire service life.

Valley plates

The NOC design team not only used conical EPS roof insulation solutions, but also opted for factory-cut EPS valley sheets from Insulfoam. “The decision to use pre-cut EPS valley slabs was possibly the biggest time-saving element of the entire NOC renovation project,” says Kris Eschmeyer, Area Sales Manager at Insulfoam. “With new pitched roof systems, building owners often have to cut each valley diagonally in half and throw away the unused piece. It is a huge waste of time and materials. “To counter this, Insulfoam offers bespoke valley plates that can be tailored to the exact project specifications. This level of adjustment reduces the amount of material wasted on the construction site. In addition, a large part of the field shortenings are eliminated, which in turn leads to savings in labor costs and speeds up the project schedule.

High performance system

The roofing membrane installed was a 90 mil gray FleeceBACK TPO manufactured by Carlisle SynTec. The newly embossed roof was completed in July 2020 after a two-year construction period. The conical EPS approach enabled the project designers to take advantage of the rigid foam material. They achieved a positive slope in fewer layers of material, creating a bias for positive drainage and achieving a high R-value in two ways. In return, the designers kept the material and labor costs in check and ensured a high-performance roof system. Like a protective blanket, the well-insulated roof system protects NOC operations for years.

About the author: Tom Savoy is the technical director of Insulfoam, a division of Carlisle Construction Materials. He has been in the EPS industry for 33 years and in the building materials sector (manufacturing and testing) for 38 years. He is actively involved in many trade organizations including ASTM, SPRI


Architect: ROOFTECH Roof Technical Services Inc., Fort Worth and San Antonio, Texas, Dachtechnik.com

General contractor: Clune Construction, Chicago, Illinois, clunegc.com

Roofer: Olsson Roofing, Aurora, Illinois, olssonroofing.com


Membrane: 90 mil gray FleeceBACK-TPO, Carlisle SynTec Systems, carlislesyntec.com

Insulation: Insulfoam IX flat and conical plates, Insulfoam, insulfoam.com

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