Virtually unknown in the United States, Passive Houses are starting to make a big impression with their small footprints.
In the famously rainy city of Portland, Oregon, everyone knows that a leaky house is a recipe for disaster. But Portland-based designer Miloš Jovanović isn’t worried so much about water seepage as the more insidious and common leakage of air from a poorly sealed building, which hinders indoor climate control and wastes massive amounts of energy.
While green building benchmarks set by the United States in recent years have contributed to some improvement in this arena, Jovanović believes the most effective criteria for energy-efficient construction can be found in Europe’s Passivehaus standard (known in North America as Passive House).
The distinguishing trait of a Passive House is the absence of a furnace. Though many green building strategies seek more efficient ways to heat our spaces, Jovanović explains, “Passive House focuses on reducing the need for heating power in the first place. A building designed to this standard uses 90 percent less energy, at which point you can heat an entire house with a hair dryer.”
Jovanović’s first foray into Passive House principles began when his firm, Root Design Build, was commissioned to design a residence on a plateau site above Oregon’s Hood River. That project is due to be completed in the spring of 2010. Having previously designed Portland’s first LEED Platinum home, Jovanović had experience working with a catalog of sustainability guidelines, but he relished the simplicity of the Passive House system. “The standard permits a large degree of freedom in building techniques and materials,” he says, “as long as you can achieve the very strict energy and envelope requirements.”
Finding adequate materials to reach those targets wasn’t easy. The designers had to search high and low for North American manufacturers making products of high enough performance to yield an absolutely airtight seal. Jovanović attributes the shortage of available materials in part to “a lack of government support for the enhance-ment of building technologies. Europeans are much more encouraging of innovation through incentives for builders and homeowners.”
Where he has found encouragement is at the nascent Passive House Institute U.S. (PHIUS) and through conversations with Katrin Klingenberg, the institute’s executive director. Klingenberg, an architect, lives in Urbana, Illinois, in the first Passive House completed in the United States. Klingenberg designed her home in 2002 with her late husband, Nicholas Smith. Having spent seven subzero winters in Urbana, she can attest that the 1,200-square-foot house remains plenty warm, thanks to 12-inch wall cavities packed with high-density blown-in fiberglass and four additional inches of foam on the exterior of the stud wall. In summer triple-paned windows and a 14-inch polystyrene pad below the foundation obviate theneed for a mechanical air conditioner. To eliminate penetrations in the outer skin, a blower door test checks for leaks by depressurizing the house, detecting spots where air sneaks in.
Having a sealed house may sound about as delightful as living in the aft cabin of an airplane, but Passive Houses boast superior interior air quality, thanks to recovery ventilators—–special fans that draw in a steady breeze of fresh air while discharging stale air. To help condition fresh air before it circulates through the house, a 100-foot-long air tube runs underground to capture the constant temperature below the frost line.
Klingenberg’s home has performed very closely to the predictive calculations used in its design—–consuming about 75 percent less energy than a comparable Urbana house. While there are still fewer than 15 of these structures in the United States, Klingenberg says she gets over 100 inquiries daily from builders and bureaucrats asking about the amazing house that needs no boiler or air conditioner. In her explanation, she points to the 15,000 to 20,000 Passive Houses that have been built in Europe in the two decades since the system first gained prominence and shares the documented research that has come from having such a sizable test sample. The European Union–funded research revealed that unlike LEED-certified buildings, which have shown discrepancies between energy modeling and real-world performance, Passive Houses are highly successful in meeting the energy consumption levels specified by the standard.
As debate heats up over the stringency of LEED’s energy requirements, Passive Houses have an opportunity to gain a foothold in the United States. By adding a photovoltaic system, Klingenberg says, a Passive House can meet the carbon-neutrality benchmark for 2020 laid out by the 2030 Challenge, an ambitious goal supported by the U.S. Green Building Council.
Though Jovanović and Klingenberg are part of a very small army of North American Passive House advocates, they both have confidence that the system will prove itself. A 75 percent reduction in energy bills is a good start, but the designers know that examples of stellar design will also be key to convincing the curious. As the Shift House reaches completion and other new Passive House projects get under way, they’re eager to demonstrate that a supersealed space is the quickest route to a sustainable—–and comfortable—–future.