“Green Design: Utility Poles and Prairie Grass”
by: C.C. Sullivan
Published in Architecture magazine
RDG / Iowa Association of Municipal Utilities office and Training Facility, Ankeny, Iowa
Occupying a transitional moment between restored tall-grass prairie and a grid of power poles, an office and training facility for utility workers near Des Moines synthesizes the centuries-old story of its Midwestern land: the sod huts of early settlers, the agrarian grid imposed on a rambling open plain, even modern sprawl. Drawing from historical building patterns and the Jeffersonian awes, Des Moines-based RDG delineates a truly prairie-style experiment in sustainable design.
As seen in traditional farmsteads, the north and west facades serve as a windbreak to buffer winter gusts; the southern exposure welcomes the sun. Modified by topographic determinants like water runoff for a new septic wetlands, this east-west axis organizes the facility in plan and elevation. The result is a massing of two simple sheds set on a slight rise. At about 11 feet, their eave height will peek just slightly over the stalks of native big bluestem grass planted on the site to restore the natural prairie.
To effectively shield the northwest breezes, the north and west walls feature tinted concrete block with raked joints. Elsewhere, simple stud framing is clad with a natural gray cement-board siding made from recycled waste wood and Portland cement, accented by exposed rods and turnbuckles to improve wind loading on a few structural bays. Holding up a southern beam line are rough-hewn wood columns that mediate eloquently between the natural and developed spheres-are they trees or the ubiquitous utility pole?
It doesn’t really matter. “We just wanted to keep the materials as honest as possible, much as farmers would, or as utility folks would do with their buildings,” says RDG design partner Kevin Nordmeyer. The approach also reduced cradle-to-grave impact. For example, the unfinished Galvalume roof structure and flashings simplify future recycling. Other “closed-loop” materials abound, such as recycled concrete, recyclable carpeting, and roof insulation from reclaimed extruded polystyrene.
Orientation and fenestration produce a bright, open-plan interior, painted white in part to recall the whitewashed interiors of early sod huts on the plains. “The building is 96 percent daylit, including storage rooms and a large auditorium,” says Nordmeyer. Office and common areas frame vistas of the sky and the landscape. To control glare, east-west exposure is minimal, and two levels of windows are employed -high-bays overhead for daylighting and a second rank below eye level “so that when you’re sitting at your desk, you can see outside.” Deep overhangs and seasonal light baffles on the southern façade control direct sunlight. The expected active energy-conservation systems (many recommended by Minnetonka, Minnesota-based energy consultant Weidt Group) are in ample evidence: occupancy sensors, photosensors, time clocks, and dimmable fluorescent fixtures.
Mechanically, the facility’s connection to the land is indeed literal. Below grade, a ground-source heat pump transfers heat to cool or warm interior spaces. (The geothermal installation cost $25,000 more than a typical rooftop system, but it offered an attractive three-year payback.) Because site conservation was the project’s focus, a horizontal loop of piping, which would require that much of the site be excavated, was ruled out in favor of a vertical-loop arrangement of 38 wells drilled to about 250 feet below grade.
In fact, the urge to minimize grading and conserve the site’s natural features dictated numerous design moves and construction methods. The architects specified that excavation fill be used for new wetlands, siltration ponds, and a wetlands septic system-a biological approach that treats building wastewater on site. The contractor tilled donated compost into graded embankments to create the siltration ponds, and the architect secured variances for parking and driveway designs that allow natural infiltration and drainage into the wetlands. The carefully restored tall-grass prairie helps prevent soil erosion by wind and water, while also creating habitat and reintroducing native plant species depleted by years of agriculture.
LEED or follow?
Ironically, the site-conservation techniques run counter to recommendations from the U.S. Green Building Council’s widely used LEED Rating System: The project, which predates the LEED program, took farmland out of production and impinged on natural wetlands – both Green Building Council no-nos. Yet, the project saved the site from planned warehouses and surface parking and from runoff that was sitting into the existing wetlands, “restoring the property to what it was like 150 years ago, when it was taking care of itself,” says Nordmeyer. Thus, the demonstration project – with its panorama of coneflowers, goldenrod, and compass plant blooming in the spring – offers insight into the widely leveled criticism that LEED ratings don’t travel well.
Iowa Association of Municipal Utilities Office and Training Facility, Ankeny, Iowa
Client: Iowa Association of Municipal Utilities
Architect: RDG, Des Moines – David Dulaney (principal); Kevin Nordmeyer (designer); Rich Gardner (landscape architect)
Engineers: James Wilson (structural); Alvine and Associates (M/E/P); Gjersvik & Associates (civil)
Consultants: Weidt Group (energy); Stecker Harmsen (cost); Polk County Conservation Board (planning); Prairie Roots Restoration (plantings)
General Contractor: Story Construction
Area: 13,500 square feet
Cost: $1.9 million
Photographs by Assassi
Concrete Block: Rhino Materials
Cement-Board Siding: Viroc, Allied Building Products
Roofing: Berridge, Firestone
Doors: Curries, Weyerhauser
Closers/Exit Devices: Sargent
Acoustical Panels: Tectum
Paints/Stains: ICI Devoe
Carpet: Blue Ridge Commercial
Lighting: Lithonia, Stonco, Cooper
Lighting Controls: Wattstopper
Plumbing Fixtures: Kohler
Heat Pumps: Water Furnace
Energy Recovery: Green Deck
Electrical System: Cutler-Hammer
Fire Alarms: Simplex