“Who wouldn’t want to work on a Bunshaft building?” asks architect Rod Kruse, a principal at BNIM. The rhetorical question is Kruse’s way of explaining why he was so pleased that insurance provider American Enterprise Group (AEG) chose his firm to renovate its headquarters in downtown Des Moines. The 153,000-square-foot office building, completed in 1965 and designed by renowned Skidmore, Owings & Merrill (SOM) partner Gordon Bunshaft, was highly unusual for its time. Built for American Republic Insurance (now an AEG subsidiary), the eight-story edifice has minimal internal structure, being supported almost entirely by its east and west poured-in-place concrete walls that are lifted above the ground plane on giant steel “knuckles.”

This configuration creates a strong, stark form. But the scheme also allowed a 90-foot clear span that, in turn, provided an open, flexible workspace, anticipating current office design trends. And with private offices placed around the core, it gave workers daylight and views through the unobstructed north and south glazed elevations.

Over the years, the owners had made some changes, such as substituting cubicles surrounded by tall partitions for the original open work-area desks, but they had, for the most part, maintained the building’s defining characteristics. However, by the time the structure approached the half-century mark, the interior finishes were badly deteriorated and its mechanical systems were outmoded, making it impossible to maintain comfortable temperatures. The joke among employees was that they could experience all four seasons in one day without ever going outside, says the AEG executive who oversaw the renovation, Medha Johnson, vice president for human resources.

The revitalization project, completed last August, remedied the situation with state-of-the-art systems as well as improvements to the building envelope, including replacing the original single glazing with insulated glazing. The architects designed the new mullions so they appear identical to the originals on the exterior. BNIM estimates that such changes will save the client $2 million each year in energy and maintenance costs. The building’s new plumbing has already saved AEG a considerable sum, having reduced the water bill from $22,000 to $5,000 per month, says Johnson.

Updating the infrastructure could have compromised such hallmark features as the ceilings of precast concrete Ts. Here SOM had ingeniously integrated ductwork and lighting to make a series of illuminated coffers. The renovation team recreated the effect with LEDs, but also invisibly incorporated sprinklers and cables for data. BNIM’s trick was to reconstruct the cylindrical ducts with a slightly chamfered top, creating a spot to conceal the new equipment.

Replacement of the systems required significant interior demolition. Afterward, contractors meticulously rebuilt walls and applied finishes. The renovation team also restored or replaced many of the original furnishings, which had been selected or custom designed by SOM—but now AEG employees who occupy the open office areas have BNIM-designed ergonomic work­stations with sit-stand desks. In keeping with Bunshaft’s concept, these have low dividers so as not to impede the daylight and views.

Since the renovation, the building has been listed on the National Register of Historic Places—a testament to how faithful the project team was to the original. This status allowed AEG to take advantage of state and federal preservation funds. The grants, along with other sources, including a local jobs incentive and state economic development tax credits, paid for half the $30 million construction cost.

Johnson guesses that AEG could have built a new headquarters for $15 million, “though it would have been obsolete in 10 or 15 years,” she says. Instead, the renovation has given Bunshaft’s building another five decades, according to Kruse’s estimates. His hope is that BNIM’s interventions are nearly imperceptible. If he’s done his job right, he says, “most people won’t even realize we’ve been here.”  

Back to Good Design Is Good Business 2016



BNIM, 317 6th Avenue – Suite 100, Des Moines, IA 50309-4127

Personnel in architect's firm who should receive special credit:

Rod Kruse, Principal, FAIA
Kevin Nordmeyer, Principal, AIA
Carey Nagle, Associate Principal, AIA
Paul Kempton, AIA
Tina Wehrman, IIDA
Levi Robb, Assoc. AIA
Kayla Ohrt, Assoc. AIA
Dana Sorensen, Assoc. AIA
Jeff Shaffer, Assoc. AIA
Lana Zoet, Assoc. AIA
Phil Bona, AIA

Interior designer: BNIM – http://www.bnim.com


Mechanical Engineer: Design Engineers - http://designengineers.com
Structural Engineer: Charles Saul Engineering - http://www.csengr.com
Electrical Engineer: Design Engineers - http://designengineers.com
Civil Engineer: Snyder & Associates, Inc - http://snyder-associates.com


Lighting Designer: 

Design Engineers - http://designengineers.com

Owner Representative: 

Christensen Development - http://www.christensendevelopment.com

Historic Preservation: 

Christensen Development - http://www.christensendevelopment.com

Architectural Historian: 

Jennifer James Communication LC

Code Consultant: 

FP+C Consultants, Inc. - http://www.fpc-consultants.com


BNIM - http://www.bnim.com

Building Energy Consultant:

The Weidt Group - http://theweidtgroup.com

Acoustical and A/V Consultant:

The Sextant Group, Inc. - http://thesextantgroup.com

Electrical Contractor: 

Baker Electric Inc. - http://www.bakerelectric.com

MEP Contractor: 

Baker Group - http://www.thebakergroup.com

Commissioning Consultant: 

SystemWorks LLC - http://systemworksllc.com

Historic Concrete Restoration Consultant: 

Structural Engineering Associates, Inc. - http://www.seassociates.com

Curtainwall Contractor: 

Architectural Wall Systems Co. - http://www.archwall.com

Interior Glazing Contractor: 

Elite Glass & Metal LLC - http://www.eliteglassandmetal.com

Door Hardware Consultant: 

Walsh Door & Hardware - http://www.walshdoor.com

Furniture Vendor: 

Saxton Inc. - http://www.saxtoninc.com

Fire Protection: 

Viking Automatic Sprinkler Co. - http://www.vikingsprinkler.com

Elevator Vendor: 

Schindler Elevator - http://www.schindler.comus/internet/en/home.html

Kitchen Consultant: 

Boelter Companies - http://www.boelter.com

General contractor: Ryan Companies US, Inc. - http://www.ryancompanies.com


Construction Photographer:

Multivista Systems LLC - http://www.multivista.com     


Hedrich Blessing Photographers - http://hedrichblessing.com




Exterior Cladding

Metal/glass curtain wall:

Architectural Wall Systems - http://www.archwall.com

Other cladding unique to this project:


Knauf Insulation - http://www.knaufinsulation.us/



UltraPly TPO Firestone Building Products Company


Glass: Exterior:
Guardian Glass - https://www.guardian.comGuardianGlass/index.htm

Crista Curva - http://cristacurva.comen/


Insulated-panel or plastic glazing:


Entrances: Revolving Door:

Dorma USA Inc. - http://www.dorma.comus/en/

Metal Doors:

Ceco Door - http://www.cecodoor.comen/site/cecodoor/

Metal doors:

Ceco Door - http://www.cecodoor.comen/site/cecodoor/

Wood doors:

Eggers Industries - http://www.eggersidustries.com

Sliding doors:

Hufcor – http://www.hufcor.com


Locksets: Schlage - http://us.allegion.com

Interior Finishes

Acoustical ceilings: USG - https://www.usg.com

Suspension grid: USG - https://www.usg.com

Demountable partitions:

Architectural Wall Systems - http://www.archwall.com

Trendway - http://www.trendway.com

Cabinetwork and custom woodwork:

Architectural Arts - http://www.architecturalarts.com

Paints and stains:

Sherwin Williams - http://www.sherwin-williams.com


Invision - http://www.jj-invision.com


Office furniture: Office furniture:
Knoll - http://www.knoll.com


Elevators/escalators: Schindler Elevator - http://www.schindler.comus/internet/en/home.html


Energy management or building automation system:Alerton - http://alerton.comen-us/pages/default.aspx