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Innovative Roofing System Keeps New Terminal Roof High and Dry
One might assume that rain and standing water would rarely be problems for an airport located in the "Valley of the Sun." But it does rain in Phoenix, often very fast and very hard. And though water is a precious commodity in the desert Southwest, nobody wants to find it ponding atop Terminal 4’s low-sloped roof system. That’s why DWL Architects & Planners, Inc., the firm that designed Terminal 4, needed a roofing system that would quickly and efficiently drain stormwater, yet also have the strength to withstand wind load uplifts from jet blasts on the nearby runway. The DWL design team specified a single-ply roof membrane with a ballasted paver system using lightweight concrete pavers and metal tie-downs installed over tapered polyisocyanurate (polyiso) insulation panels. "Single ply roofs such as this are expensive, but they last a long time," says Project Architect Steve Rao. "You want a roof like this to last 40 to 50 years." To make sure that the roof would stand up to the demands of time, the elements, and powerful jet engines, two key products from Atlas Roofing Corporation were selected: ACFoam-II polyiso insulation panels, and Gemini™ Pre-Cut Crickets, the roofing industry’s first and only pre-cut hinged system. ACFoam-II may be used with BUR, modified bitumen, and single-ply systems. Polyiso is the most popular and accepted rigid insulation in use today; research by the National Roofing Contractors Association (NRCA) indicates that nearly two-thirds of all new or reconstructed commercial roofing systems use polyiso. To direct rainwater runoff from portions of the 60,000-square-foot roof surface into the drainpipes, a "2-way to drain" system was designed–a tapered two-way slope that uses crickets to prevent ponding. "You need the water to get into the drains, but you don’t want the slope right at the drain," Rao explains. Though not quite as efficient as a "four-way to drain" configuration, the design is less expensive and can eliminate the potential for ponding on low-slope roofs when properly designed and installed. In the past, there was another trade-off in constructing this kind of drainage system: the time-consuming, labor-intensive process of fabricating, cutting, and installing the crickets themselves. But with Atlas’ Gemini Crickets, the ease of installation amazes even veteran roofing contractors. Gemini crickets are hinged, easy to drop into place, and fit with the standard Atlas tapered panels. Available in 1/4-inch and 1/2-inch-per-slope versions, the crickets’ hinged triangular sections fold into one piece for easy and fast installation. Gary Taylor, president of Taylor Enterprizes of Litchfield Park, AZ, the roofing contractor for Terminal 4, notes the Gemini crickets provide multiple benefits for the contractor. Chief among them is that Atlas crickets are pre–manufactured and pre-packaged, easy to use and install. With time being perhaps the most critical factor for nearly every type of roofing project these days, Taylor appreciated having a product that helped his roofing crews get the work done quickly. "We could have field cut any type of crickets for the Terminal 4 project," he says, "but it would have been very labor intensive and probably cost as much or more than the Atlas crickets. It was much easier to simply open the box, fold them to their full size, and install them. It saved us a lot of time."
Terminal 4’s rooftop drainage system uses a base of 4-foot by 4-foot ACFoam-II‚ pre-cut insulation panels together with the Gemini crickets, creating a gentle slope to divert water to perimeter drains set back 2 to 4 feet from the roof’s edge. The insulation is covered with a TPO membrane, topped with Lightguard ® roof insulation, a polystyrene/latex modified concrete composite. Metal straps hold the entire assembly down. Gemini™ Pre-Cut Crickets also saved Taylor and the airport another valuable commodity: space. Full-customized crickets require up to eight weeks of lead-time, then arrive by the pallet-load, taking up valuable space at the jobsite. Gemini crickets, on the other hand, are small and compact, and come in easy to handle boxes. The hinged three-panel cricket unfolds in a snap, and requires only minimal trimming–if any–at the ridge line. There are no small pieces to deal with and no confusing assembly plans to decipher. And for those instances where shop drawings don’t match field conditions, Gemini crickets can be adjusted in seconds.
Taylor adds that using Atlas Roofing Products on Terminal 4 was as natural as sunshine in the desert. "Atlas is the company I usually go with on all my jobs." |
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Project Information Project: Related Products
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In 1999, Phoenix International Sky Harbor Airport completed a much-needed expansion to Barry M. Goldwater Terminal 4. Named in honor of Arizona’s longtime U.S. Senator, the 2.4-million-square-foot terminal contains a concourse with 12 gates and the capacity to add two more in the future. An adjacent four-level, 3,400-space parking structure provides easy access to the terminal, ensuring that the airport will continue to meet the transportation needs of the fast-growing region well into the future.
How much time? Obviously, designs vary depending on the size of the roof and the drainage system. But with Gemini™ Pre-cut Crickets, "one person can install a 20-foot cricket in as little as 15 minutes," says Tom Urich, an independent sales representative who assists Atlas’ customers throughout the Southwestern U.S. He adds that the unique design of Gemini crickets provides another important environmental benefit: waste reduction. "Fabricating crickets at the job-site creates a lot of leftover material that usually goes to the dump," he says. "On the other hand, Atlas pre-cuts only the key parts of Gemini crickets. Contractors then fill in the remainder of the cricket structure with standard ACFoam-II panels."
Such convenience was important for the roofing crews, given that Taylor’s roofing crews had to literally "wrap up" the project at the end of every work day. "Terminal 4 was a difficult job because we had to tie everything down to keep jet-driven debris from littering the airfield," Taylor explains. "With the pre-cut material from Atlas, we could get the work done quickly. These features were very valuable on this job."