Even if the Iowa Utilities Board/Office of the Consumer Advocate office building in Des Moines had merely achieved its energy-efficiency goal of 28 kBtu per square foot per year, it would have meant an impressive 69 percent reduction from baseline energy code. After all, the building was LEED Platinum–certified and earned a slot on the AIA/COTE Top 10 Green Projects list in 2012.
But after two years of occupancy, the Utilities Board/Consumer Advocate headquarters has performed substantially better, consuming only 16.7 kBtu per square foot per year, equivalent to an 81.5 percent reduction over the national average. While its original LEED Platinum rating came from a carefully orchestrated integrated design—including optimal solar orientation, a highly insulated precast concrete and glass envelope, and geothermal heating and cooling—the architect, BNIM, and the client agree that the reason for the added efficiency is occupant buy-in and participation. Through opening and closing the 44,640-square-foot building’s operable windows and shades, and by giving up a few creature comforts, employees have made the building continually responsive to changing conditions—and now a COTE Top Ten Plus winner.
“Before we moved in, we worked on protocols on how we would behave,” recalls Judi Cooper, deputy executive secretary for the Iowa Utilities Board. “I think that’s in big part why the building operates as it has. We all agreed from top to bottom we’d abide by these rules.” When exterior conditions are favorable, for example, the building’s automation system emails occupants instructions to open windows, an action that automatically shuts off heat pumps. Employees also control operable shades in order to mitigate glare coming from the floor-to-ceiling windows.
To minimize plug loads, extra personal items such as space heaters and refrigerators were banned. Two types of plug-ins were created: one for critical equipment that has to run continuously, such as computers, and another for everything else which are connected to occupancy sensors. According to BNIM principal Rod Kruse, FAIA, the project was one of the nation’s first to include sensors at every workstation. The one drawback, he jokes, is that “if you snooze at your desk, all your outlets will go to sleep and people will know you’re not working hard.”
Surpassing the project’s already ambitious efficiency goals seems to validate its robust insulation that wraps uninterrupted from the roof into the wall panels and around the foundation. “We kept hearing, 'You’re at the point of diminishing returns on the insulation,'” remembers BNIM’s Carey Nagle, AIA, the project’s lead designer. “But we were pretty passionate about avoiding thermal bridges. The biggest [bridge] is where a roof intersects a wall or a slab on grade intersects an interior wall. We developed details so that insulation is uninterrupted at every surface. We had to make wise choices, but we knew that adding that extra layer of insulation would pay off.”
Nagle also stresses how integrated design meant computer-modeling every aspect of the building together in order to find added efficiency opportunities. “Too often you don’t understand enough the multiplier effect,” he says. “Strategies looked at in isolation don’t look as good as they might when you consider the impact to other systems.”
Constructed for approximately $226 per square foot, the Iowa Utilities Board/Office of the Consumer Advocate was envisioned as a demonstration project that wouldn’t be cost-prohibitive to achieve. “For a class-A office building, it’s a fairly competitive price,” Kruse says, “and it’s saving around $50,000 a year on utilities.”
Fine-tuning was still necessary. A third-party daylighting assessment showed more shading devices were needed and more user accessibility to controlling motorized shades, especially when the severe winter of 2013–14 created added glare from reflective snowfall for weeks. “I think if we’d have done one thing differently, it would be using more Solatubes with dampers on them to dim the lights,” Kruse says of the offices’ many small skylights. “We didn’t do that over workstations.”
Even so, employees are thriving on the light after moving from a dark converted warehouse. “I think there may have been 11 windows in the entire building,” Cooper recalls. “Most people never saw the light of day. It was an adjustment to come from what I’d call a cave to a daylight filled building, but frankly it’s been very helpful in recruiting. People walk in and think, ‘Wow, I’d like to work here.’ ”
Click here to access our coverage of the Iowa Utilities Board/Office of the Consumer Advocate Office Building in 2012. Click here to see all of the 2014 AIA COTE Top Ten Green Projects. Scroll down for more images, along with performance data and project team and materials information. Stay tuned for profiles of this year's winning firms on Ecobuildingpulse.com, along with additional coverage of this year's Top Ten in the Spring issue of ECOBUILDING Review.
BY THE NUMBERS
Project completion date: January 2011
Building gross floor area: 44,640 square feet
Estimated percent of occupants using public transit, cycling, or walking: 22
Daylighting at levels that allow lights to be off during daylight hours: 98
Lighting power density (watts per square foot): 0.75
Percent of views to the outdoors: 98
Percent of spaces within 15 feet of an operable window: 53
Percent reduction of regulated potable water: 46
Potable water used for irrigation: No
Percent of rainwater from maximum anticipated 24-hour, two-year storm event that can be managed on site: 36
Total EUI (kBtu per square foot per year): 22
Net EUI (kBtu per square foot per year): 16kBtu/sf/yr (estimated at 20kBtu/sf/yr in 2012 COTE Top Ten documents)
Percent reduction from national median EUI for building type: 80 (estimated at 49% in 2012 COTE Top Ten documents)
Third-party rating: LEED v2.2 Platinum
Total project cost as time of completion (land excluded): $10,127,923
Data provided by AIA.