Imagine spending a long Illinois winter in a cozy house with no cold corners or drafts—and heating bills half the norm—or sailing through a sultry Louisiana summer in cool comfort with bills that cost a fraction of the neighbors’. Passive House, the latest set of building standards sweeping North America, uses seven simple principles to make these housing dreams come true.
Passive Houses are so well designed, insulated, sealed and ventilated that they require as little as 10 percent of the energy standard homes use for heating, cooling and lighting. A tight envelope (roof, exterior walls and floor) and thick, heavily insulated walls keep winter cold and summer heat at bay with little reliance on furnaces and air conditioners. In winter, Passive Houses hold in heat from the sun, inhabitants’ bodies, lights and appliances. In summer, they keep cool air in and hot air out, though additional cooling may be needed in very hot, humid climates. Energy-recovery ventilators (ERVs) circulate fresh air for even temperatures and humidity.
Though the movement traces its roots to the American superinsulated house movement of the 1970s, the Passive House principles were further developed and codified by German professors Wolfgang Feist and Bo Adamson in the 1980s and 1990s. Using the standards of the Passivhaus Institut (PHI) founded by Feist in 1996, thousands of European homes have been built or remodeled, and many provinces and cities require projects built with public monies to achieve PHI certification. Architect Katrin Klingenberg brought the Passive House movement to the United States, co-founding the Passive House Institute United States (PHIUS) with builder Mike Kernagis in 2008. Close to 60 Passive House projects have been completed or are underway around the country.
In Europe, the Passivhaus Institut has worked out many of the system’s kinks, but the United States encompasses a different range of climates, aesthetic tastes, and financial and property practices. Every U.S. Passive House breaks new ground. With Passive House construction costs at 6 to 15 percent above average, early adopters must be committed to long-term, deep energy conservation and be willing to work out the bugs for the rest of us.
Margaret and Gregory Stanton, who built a Passive House in Urbana, Illinois, don’t feel altruistic. “We’re selfish,” Greg jokes. “We’re free from volatile energy prices.” The Stantons love their thick walls and deep windowsills, energy savings and the absence of drafts. In response to Urbana’s cold winters and hot, humid summers, the Stanton house has R-87 roof insulation (20 to 24 inches of loose-fill cellulose), 18-inch-thick R-64 walls and a thick slab floor insulated to R-51. Direct solar gain provides much of their heat, backed up by a heat pump and an inline heater in their ERV. The Stantons collect rainwater to irrigate their garden, use solar-thermal panels to heat their water, and salvaged much of the wood from the original house on their 2.5 acres.
Passive Houses are popping up all over. “Passive House has exploded in this country,” Kernagis says. “In 2008, there were 15 certified Passive House consultants in this country. Now there are 275, and we’re training more.”
Kernagis has seen public and professional opinion about Passive House evolve from apprehension to growing acceptance, and he hopes that someday the standard will be written into building codes and municipal mandates. “People resonate broadly with our building energy metric,” he says.
The standard’s best advocates, Kernagis says, are Passive House homeowners. “They’re just so happy, and they want to tell people about it.”
A Passive Retrofit
In Sonoma, California, Rick Milburn of Solar Knights Construction is using the Passive House standard to upgrade Catherine O’Neill’s home. The 1962 bungalow—the first Passive House Institute U.S.-certified retrofit—uses about 70 percent less energy than its neighbors. “People think these things are complicated,” Milburn says, “but they’re supersimple.” The O’Neill home is insulated to a standard unusual in California: R-74 roof, R-31 walls, and R-12 to R-20 floors (Energy Star recommends roof insulation of R-30 to R-60). A solar-thermal array heats water and spaces. “In California, we don’t need furnaces or air conditioning if we build right,” Milburn says. “If we just lower the load, we don’t have to spend trillions on our utility grid.”
Coolin’ on the Bayou
University of Louisiana architecture professor Corey Saft used the Passive House standard when he built a rental property known as 204House on the lot he owns next door to his Lafayette home. He admires the standard for its simplicity, calling it “an understandable, knowable metric.”
Renters have lived in 204House for almost a year. “The renters love it,” Saft says, “and we’ve shown that not only can Passive House principles work in this climate, but that they also work financially.” Despite its 10 percent higher-than-average construction costs, 204House’s market-rate rental income covers expenses, with money left over for repairs. In fall, spring and part of the winter, the home’s utility bills are extremely low—averaging less than $10 a month. Saft monitors the house’s performance and tweaks ventilation to optimize comfort and energy efficiency.
Passive House Institute United States (PHIUS)
Corey Saft, RA, LEED AP
Lail Design Group
St. Helena, California
Solar Knights Construction
Homes for a Changing Climate: Passive Houses in the U.S. by Katrin Klingenberg, Mike Kernagis and Mary James
Recreating the American Home: The Passive House Approach by Mary James
Low Carbon Productions
Architect Carol Venolia, co-author of Natural Remodeling for the Not-So-Green House, writes Natural Home’s “Design for Life” column.