The new FedEx Cargo Facility at O’Hare Airport in Chicago is an impressive design response to the sustainable vision promoted by the City of Chicago’s O’Hare Modernization Program (OMP). The 363,320-gross-square-foot development includes four buildings: the World Service Center (WSC)/administration building, aircraft maintenance building, vehicle maintenance building and sort building. A 300-foot pedestrian bridge connects the WSC with the sort building, which contains the material handling systems and sortation matrix as well as support spaces.
But what’s most interesting about the project is what connects the WSC, sort building and vehicle maintenance: the largest continuous vegetated roof at any airport in the world, totaling 174,442 square feet.
Located next to an active runway, the design team sought a roofing system that would meet the challenging demands of an airport environment. The roof needed to be wind resistant and leak proof, fall under a unified warranty (covering water tightness, success of plants, and overburden removal and replacement), and allow for easy identification and quick repair so that FedEx operations would never be compromised.
The optimal green roof system was chosen to be a Sarnafil PVC (thermo-plastic) roof membrane with Xero Flor Vegetated Mat. The waterproof membrane layer was designed for Factory Mutual (FM) 1-35 data sheet standards, with FM tested 1-60 adhered roofing assembly and an integrated conductive layer for electronic leak detection. The membrane is fully recyclable at the end of its life. The vegetated mat layer was rolled out for quick installation, thereby satisfying stringent technical standards specifying high early resistance to windborne debris; there could be no risk of materials blowing off the roof and onto nearby runways. Without trays, the vegetated layer was quickly fixed to restraints, providing an instantly robust layer that would grow out and around patented anchors and disks.
An experienced team of green roofing and roof membrane specialists provided technical support, while innovative contractors detailed, fabricated, installed and tested the roof system. Challenging the installation were the use of the roof as a staging area during construction and the demands of Chicago’s unforgiving winters. The green roofs of the 25,000-square-foot vehicle maintenance facility and 24,000-square-foot WSC were completed in one day, and the green roof of the 300,000-square-foot sort building was finished in just 17 days.
The entire green roof is comprised of 3.9 acres of cultivated pre-vegetated mat with restraint anchors and more than 2,200 cubic yards of growing media plus 3.1 miles of aluminum edge treatment. The largest continuous roof area is the 724 feet by 224 feet over the sort facility. The entire roof is estimated to have a saturated weight of 4.3 million pounds and to retain 2 million gallons of stormwater annually. It also meets the OMP’s sustainability goals to reduce the urban heat island effect. Since its completion in summer 2010, the roof has withstood two severe wind events with no damage.
While adding to the sustainability of one of the nation’s busiest airports, the massive green roof beautifies a large and prominent facility by providing a seasonal display of native foliage year round.
Green Roof on the FedEx Cargo FacilitySize: 174,442 square feet
Green Roof Type: Extensive
Owner: O’Hare Modernization Program, the City of Chicago
Architect: Solomon Cordwell Buenz (SCB)
General Contractor: Power Construction Company and Ujamaa Construction (a project-specific joint venture)
Green Roof Consultant and Installation: Intrinsic Landscaping Inc.
Roof Contractor: All American Exterior Solutions
Green Roof Manufacturer: Green Roof Solutions
Waterproofing Roof Membrane: Sika Sarnafil
Landscape Architect: Site Design Group
Vegetation Mat: Xero Flor America, Xero Flor XF301
Green Roof System Base Assembly: Green Roof Solutions Terra Roof
Additional information was provided by www.greenroofs.com.