The Hamad International Airport in Doha, Qatar is impressive by any measure and distinctive for many reasons, including being the largest stainless steel roofing project in the world. Installation of the 3.8 million square feet of roofing material began in 2007 with the specification of InvariMatte, the signature stainless steel product of Contrarian Metal Resources, Allison Park, PA.
When the decision to build the new airport was made, Qatar officials set out to create a world-class facility that would leave a favorable impression with all who passed through it. In the process, they set new global standards for operational efficiency, passenger convenience and service. To boot, its gulf-side location offers spectacular, sweeping views.
Since 2004, HOK Architects, engineers, planners, landscape architects and interior designers have collaborated in an effort to create the world’s best, most state-of-the-art passenger terminal. The first phase includes multi-concourse Terminal One; an Emiri Terminal for state visitors, which includes its own aircraft apron, vehicle rental and car facilities; an enormous maintenance hangar capable of serving 13 aircraft simultaneously; a cargo terminal which will handle 1.4 million tons annually; and on-site catering facilities which will produce 90,000 meals daily (the prepared food will be loaded onto the aircraft before takeoff).
InvariMatte® was specified as the roofing material for its aesthetic value and glare resistance. InvariMatte® is a low gloss, uniformly textured stainless steel with no coatings to deteriorate, designed for use in architectural applications.
Contrarian began working with the airport’s architects at the earliest stages of design to identify the type of material needed for the project. They had to supply a material solution that would withstand the environment in the Middle East. Its Gulf location presented challenges that had to be overcome. Type 316L stainless steel, which is suitable for most marine locations, would not withstand the environment which includes severe dust storms as well as intense salty air.
Contrarian’s team believed that titanium was the answer, but discovered that there was little available at the time of production. Rising to the challenge, Contrarian teamed up with ATI Flat Rolled of Brackenridge, PA to identify a stainless steel that would perform in that challenging environment. The solution was ATI 2003™ lean duplex alloy, a new stainless steel alloy at the time. ATI 2003 offered better corrosion resistance and strength compared to Type 316L. “Duplex alloys are typically used in severe corrosion applications like off-shore drilling rigs, but they’re generally tough to form, making it challenging to produce a standing seam roof. However, lean duplex alloys have better forming characteristics and retain the advantages of the duplex grain structure, which helps with strength and corrosion resistance, but has enough elongation to make a standing seam roof,” said Jim Halliday, President of Contrarian. “ATI’s development of the alloy was the key to our success,” he continued.
The next objective was to develop a process to produce a low-glare finish on the alloy. InvariMatte® was specified but it had never been produced in a duplex alloy, although it had been used on austenitic Type 304 and Type 316 stainless. The methodology was established for the finish to be applied to the ATI 2003™ lean duplex alloy. This cuttingedge development has resulted in the first duplex roof with a rolled texture that also happens to be among the largest airport roofs in the world.
After sorting out material issues, production and installation of a standing seam roof system had to be proven before the total solution could be approved. Bemo USA developed manufacturing methods to work with this new material, even conducting wind uplift and waterproof testing prior to presenting this novel solution to authorities. “We could not have done it without Bemo’s expertise,” said Halliday.
During the project, many things were learned and one in particular stands out. Halliday was on the roof in Doha when the temperature was 118°F. He leaned over to touch the roof and was startled that the roof was not hot, but rather comfortable to the touch. He had been apprehensive when he realized he was wearing rubber soled shoes, fearing they might melt in the intense heat and stick to the roof. Discussing his findings with Fred Deuschle, Exec. VP of Operations, the pair decided to find out why the stainless was not hot. They hired an independent Ph.D., Michael McGuire, an expert metallurgist who began to study the phenomenon.
Combat Global Warming & Save Energy with Stainless Steel
The research determined that stainless steel plays a significant part in global cooling and conservation. The Solar Reflectance Index (SRI) of stainless steel is near perfect and does not deteriorate over time the way that white painted metals or membrane surfaces do, nor does it emit harmful Volatile Organic Compounds (VOCs). Painted surfaces lose about 5% of their solar reflectance each year resulting in significant degradation over time. In addition, stainless steel roofs and wall systems conserve energy and contribute an insulation value to an exterior cladding system.
Accumulated dirt on the surface of a building envelope will interfere with solar reflection. This is true of any material, including stainless steel. But since InvariMatte® is designed to shed dirt with its proprietary hydrophobic micro surface texture, its solar reflection efficiency is undisturbed over time. Contrarian tested three InvariMatte® roofs in different parts of the United Sates after 10 years in service that had not been cleaned and were unable to measure any degradation in solar reflectance compared to brand-new control samples.
Beyond cooling the planet, stainless steel roofs and wall systems act as radiant barriers that conserve energy. Since stainless steel contributes to the building’s insulation system in this important way, the advantages apply to warm climates as well as cold. However, the biggest economic benefits as well as the greatest contribution to cooling the planet will be realized in hot climates.
In the past, stainless steel has been an underappreciated building material. However, more building owners and the construction professionals who serve them are recognizing the tremendous value this material represents. Beyond its impressive energy performance as a building material, stainless steel has low embodied energy compared to other construction materials including glass and painted aluminum. Provided the right alloy is used for a given environment, its durability is unquestioned, allowing stainless steel buildings to last indefinitely with low maintenance and operating costs over a service life that can last as long as the building stands. Add to that the 80% recycled content in the United States and 60% worldwide, stainless steel is a truly sustainable choice.
During daylight hours the sun bombards the Earth with solar radiation, averaging 395 Watts and peaking at 1000 Watts per meter squared. Most of this radiation is absorbed by the earth’s surface and is re-emitted primarily in the form of infrared energy which is essentially heat. Greenhouse gases absorb infrared energy and cause global warming.
If we are able to generate less heat through conservation, improvement in the global warming phenomenon would be achieved. Stainless steel provides a double benefit. Beyond its contribution to energy conservation, it reflects 92% of solar energy back into space without adding to the greenhouse heating effect (global warming).
Photographs courtesy of Bemo USA/WLL