Extensive Industrial / Commercial

Project: TWA Corporate Headquarters Building
Award Recipient: el dorado inc.
Client: TWA Lofts, LLC
Landscape Designer: Off the Grid
Irrigation Design: Jeffrey L. Bruce & Company
Technical Consulting: American Hydrotech, Inc.
Structural Engineering: Norton & Schmidt
MEP engineering: Lankford and Associates

The TWA Corporate Headquarters Building, in Kansas City, Missouri, is both a historical preservation and a sustainable design demonstration project. All design decisions had to comply with strict state and federal preservation guidelines while at the same time challenging the design team to utilize limited investment capital ($72/sf for the shell renovation) in the most innovative, environmentally conscious way possible.

Regarding the roofscape in particular, the building's perfectly flat roof posed waterproofing and aesthetic challenges since its construction in 1956. In a climate that routinely sees more than three feet of annual precipitation, flat roofs with internal drainage are perhaps not the most practical design solution. Nevertheless, being a defining characteristic of historical modernist architecture, there was no opportunity to change the building's profile. Furthermore, the best views from the building's fourth floor included north and east views of a flat membrane surface that often held ponded water until it could either evaporate or leak into the building. The black surface also added heat gain in the summer months.

The 25,000 sq. ft. green roof surface uses a lightweight engineered blend of growing media, based on German FLL standards, consisting of aggregate (such as clay, slate or shale), sand and approved organic material to a depth of 3.5 inches and cost $25 per sq. ft. American Hydrotech Inc.'s Garden Roof Assembly® system offered a tremendous opportunity to maintain an absolutely flat profile while adding two distinctly different roofscape environments, both offering significant environmental improvements. This system offered a low maintenance solution with an attractive 20 year warranty that covered the waterproofing systems, drainage, pavers and growing medium.

The landscape vision was of an elevated urban prairie, incorporating native grasses and wildflower varieties (considered very challenging in such shallow soils) into a backdrop created by four Sedum varieties. The winter season "view" was also taken into consideration; in the winter, Sedums turn red or gold, depending on the species, and compliment the reddish brown stalks of Little Bluestem. The 15,000 square feet north roof became the ideal setting for an elevated urban prairie with a small observation deck. With the addition of a second means of egress off of the east roof, 10,000 square feet of formerly unattractive, unoccupiable space became a combination of roof deck amenities and small demonstration gardens, adding insulation and reducing the amount of rain water entering the
city's overtaxed storm water system.

Both roofscapes offer habitat that supports local and transient bird populations as well as insects and migratory butterflies, most notably the Monarch Butterfly. In addition, they offer improved urban landscape views from adjacent buildings.

Early in the design process the developer and architect established a planted roof as an essential component of this renovation project. A workable budget was established early and never challenged throughout numerous "value engineering" cycles.

Respecting the architectural legacy of the original building, but opening up whole new possibilities for beauty and amenity, the TWA HQ green roof exemplifies the incredible potential of the extensive industrial/ commercial green roof.

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