Practicing ArchitecturePracticing Architecture
BNIM’s COTE Top Ten Plus Recipient Sets the Pace for Utility Efficiency
Siting, ventilation, employee controls, and other strategies make this building perform above and beyond expectations
By Kim A. O'Connell
Rather than just move into a banal “cubicle farm,” the Iowa Utilities Board and Office of Consumer Advocate (IUB-OCA) wanted its new office building in the state capital, Des Moines, to serve as a model of energy efficiency for other business and government buildings in Iowa. As a utility regulator and consumer advocate, the client wanted the project to become an exercise in walking the talk for utilities and consumers—showing that if they could be energy-efficient, others could too.
For this, it turned to AIA Firm Award recipient BNIM, which is based in Kansas City, Mo., and has an office in Des Moines, to design an office building there with a high level of sustainability and subtle elegance. Within two years of occupancy, the building so exceeded its modeled expectations that it was recently named the second-ever recipient of the AIA’s COTE Top Ten Plus award, which recognizes one high-performing building per year based on verified data collected over time.
Both elements of the building’s office program demonstrate a unique angle on the money-saving efficiency of sustainable architecture. First, since the Iowa Utilities Board is the regulatory agency responsible for policing utility companies across the state, BNIM’s building returns this favor by sending back some very small utility bill payments to the companies it’s charged with overseeing. One way the OCA protects taxpayers is by ensuring the legality of rates and practices by utility companies. But with this new building, it also safeguards the wallets of consumers by being an exceptionally efficient steward of taxpayer money spent on running the building. Through a combination of daylighting, efficient lighting technologies, high-performance windows, geothermal heating and cooling, and photovoltaic panels—along with extremely environmentally attuned occupants—the building is performing even better than expected and has been awarded LEED Platinum certification.
“We always talk about how critical the owners’ vision is, and they established the initial goals,” says Carey Nagle, AIA, project architect with BNIM. “They wanted it to not only achieve that high performance; they wanted it to serve as a case study. They also wanted full engagement from their employees, which they’ve gotten.”
A badge of honor
A COTE Top Ten Award recipient just two years ago, the IUB-OCA building was designed as two rectilinear asymmetrical wings attached by a central lobby. Ambitious from the outset, and set up to be “net-zero ready,” the building’s initial energy usage level was expected to hit about 28 kBTU per square foot per year, which was equivalent to a 69 percent energy savings beyond the national office building average. Following two years of occupancy, however, the building is consuming 16.7 kBTU per square foot per year, an 81.5 percent reduction over the national average.
The energy savings had to do with BNIM’s holistic approach to the design, incorporating passive strategies—such as those related to siting and ventilation—before relying on more active strategies.
The building has an automated system that identifies favorable weather conditions, sending an e-mail to occupants when windows should be opened and closed. The automation system also shuts down various zones' heat pumps when windows are open, which ensures that energy is not wasted. Similarly, the building has several tools to reduce overall plug load from extraneous office devices. All outlets are designated as “critical power,” “non-critical power,” or “task lighting,” and are monitored, with the data analyzed through a partnership with the Iowa Department of Administrative Services and the Iowa Energy Center. Workspace outlets are tied to occupancy sensors that shut down all noncritical loads when not in use.
“Folks have to be actively engaged in these processes,” says Nagle. “They wear it as a badge of honor. The employees didn't have to make a lot of sacrifices to achieve those performances. It showed you can be comfortable, have a great work experience, and have great architecture, too. Also, it's a reminder to keep working, because if you're sitting completely still, everything will shut down.”
The IUB-OCA building is located on a corner of the State Capitol complex atop a six-acre section of a former landfill. Like other areas of the state in recent years, the site has been prone to flooding, which made building orientation and stormwater strategies a paramount concern for the design team. The site is designed to capture and filter all rainwater through a combination of rain gardens, pervious pavement, bioswales, and a stormwater interceptor. An all-native planting scheme eliminates the need for irrigation water as well. The architects designed the building to be narrowest along the north-south orientation, providing the greatest opportunity for daylighting and natural ventilation while mitigating heat gain and glare.
White precast concrete stretches from the roof to the foundation, eliminating the thermal bridging that occurs at roof interfaces, foundation walls, and other openings. Louvered sunscreens with horizontal blades and vertical fabric panels at the south elevation block unwanted heat gain, but allow passive winter heating. In all, more than 98 percent of regularly occupied spaces have access to daylight, and all employees have access to operable windows. A roof-mounted 45 kW photovoltaic array provides 25 percent of the building's power, nearly double the 13 percent originally modeled. One change made after occupancy was the addition of roller shades on the north end to mitigate unexpected glare from the reflection of snow in the winter.
Efficient and expressive
Part of the reason that the project is being recognized now, according to Nagle, is that the architecture is not secondary to the sustainable elements. Nor is the design overtly “environmental,” with something like recycled tires or other self-consciously “green” materials and systems tacked onto the front. Just as the energy-saving measures are meant to demonstrate economic sustainability, so too did the designers seek to make the architecture simple and approachable—a symbol of the efficient use of the state’s stretched resources. The architecture is light-filled and clean-lined, with wood accents to warm the interiors. It was a tricky balance to achieve, says Nagle, but one that was accomplished by taking an integrated approach to the design.
“We looked at the architecture in the same manner [as the sustainable goals],” Nagle says. “We took these same elements, such as translucency and transparency, and looked at how they reveal themselves across the elevation. We wanted to be expressive of those performance notions without being so extremely overt. The architecture in general is a quiet architecture. There's not an opulence to it, but it's expressive of our goals.”
The IUB-OCA building is located on a corner of Iowa’s State Capitol complex on a six-acre section of a former landfill. All images © Assassi.
An all-native planting scheme eliminates the need for irrigation water on site.
Louvered sunscreens with horizontal blades and vertical fabric panels at the south elevation of each wing reflect daylight during all seasons, block unwanted summertime heat gain, and allow passive winter heating.
The vast majority of regularly occupied spaces have access to daylight, and all employees have access to operable windows.
The IUB-OCA building lobby