Project: Prescott Passive House
Architect: Studio 804, University of Kansas School of Architecture, Design & Planning
Location: Kansas City, Kan.
Building green is a noble pursuit. But the economics of sustainable construction sometimes make it a losing proposition. Just ask professor Dan Rockhill, whose acclaimed Studio 804 at the University of Kansas (KU) School of Architecture, Design & Planning completed a LEED Platinum house in 2009 that’s still on the market. The solar-powered residence has costly active systems that appraisers refuse to factor into its value. “Basically, I’m getting burned” on the investment, Rockhill says. “So this year I decided to try something different.”
His change in course was a passive house—uncommon in the U.S., but a type of construction suited for the climate in Kansas City, Kan. Completed in May, the 1,700-square-foot house in the city’s Prescott neighborhood is being certified by the Passive House Institute US (PHI), the Stateside arm of a German group that supports advancement of energy-saving technology and certifies buildings using scientific criteria.
To achieve the PHI’s standard of 90 percent energy savings for heating and cooling (compared with the average housing stock), the three-bedroom house relies heavily on two elements: an airtight envelope and a superinsulated skin. After enclosing the shell, the team pressurized the house with a blower door and, using a smoke machine, looked for telltale wisps indicating air leaks. Breaks in the seal were remedied immediately.
Heavy insulation blankets the entire house, starting with 9 inches of foam beneath the 4-inch basement floor slab—an unexpectedly large amount, but one required to meet the desired level of performance. “That’s what blew my mind the most,” Rockhill says. The 16-inch-thick walls and 22-inch-thick roof all but eliminate heat transfer through the building enclosure. Rather than frame the walls and roof with dimensional lumber, the team used engineered wood I-joists to provide thicker cavities for cellulose insulation. Even then, the walls and the roof were built up on the outside with more inches of foam before the weatherproofing membrane was applied.
The design concept works hand in glove with the passive strategy. The interior volume, with a double-height living room, allows full penetration of daylight through south-facing glass and strategically placed skylights on the north-facing roof. Triple-pane, double-insulated windows are important to the house’s energy performance. Louvers over the south-facing windows—angled to maximize winter sunlight and minimize summer sunlight—control heat gain, with concrete floors providing thermal mass. A low-maintenance screen of charred Douglas fir provides a UV-absorbent dark finish.
During the temperate months, operable windows and skylights permit natural ventilation. A mini-split heat pump, which doesn’t require ductwork, provides cooling and heating during severe temperature swings. Fresh air is supplied year-round by an energy recovery ventilator, which tempers intake air with exhaust air.
Because of its highly sustainable approach, the house has become a focus for community education. An open house marked the project’s completion for KU students, but community groups and the local USGBC chapter also are coming for tours. Says Rockhill: “It’s important for the university to take a leadership role and share with the architectural community, as well as the general public.”