By the end of this year, Passive House Institute (PHIUS) should have at least 150 consultants trained to spread the gospel about building energy-efficient houses that can maintain a comfortable indoor temperature without using furnaces or air conditioners.
The Urbana, Ill.–based Institute formed in 2007, and since January 2008 has been the exclusive U.S. certifier of homes built to performance standards set by Germany-based PassivHaus Institut. Estimates vary, but somewhere between 15,000 and 20,000 homes throughout Europe (especially in Austria) have been built to these specifications. The concept hasn’t caught fire yet in the U.S., but PHIUS, operating on a shoestring budget, is trying to spur interest through educational and outreach programs.
A passive house is an airtight structure constructed to retain as much “free” heat created inside of a house as possible. The concept, in fact, dispenses with conventional HVAC systems in favor of a heat exchanger that uses heat generated from its occupants, appliances, electronic devices, pets, and so forth, to warm fresh air coming in from outside that’s circulated through vents.
The selling point of passive design is its promise to reduce energy consumption by as much as 90 percent without relying on expensive equipment such as solar panels. The building is oriented to expose the majority of its triple-pane windows to maximum sunlight. Its hermetically sealed double wall system eliminates “thermal bridges” that allow air to escape through the shell.
To achieve certification, a house’s primary energy source can’t generate more than 1.4 kilowatt hours or 4,800 BTUs per square foot per year; its maximum total “source energy” (the energy required to produce and deliver energy to the site) can’t exceed 11 kilowatt hours or 38,000 BTUs per square foot per year; and its air leakage must stay below 0.6 air exchanges per hour at 50 pascal units of pressure. (By comparison, Energy Star allows seven air changes per hour.)
Lance Wright can attest to how effective passive construction can be. A former forester and political activist in Denver who at presstime was close to becoming a PHIUS consultant, the 57-year-old Wright built his 2,100-square-foot home to PassivHaus standards, using a thermal water heater as its primary energy source. During 90-plus degree summers, his house’s temperature hovered around 73 degrees. And when Denver’s frigid winter temps dropped to 15 below zero, Wright’s house didn’t get colder than 62 degrees.
“It’s amazing what solar gain and well-insulated windows can do,” says Keihly Moore, assistant director of Passive House Institute’s E-Co Lab.
As of September, the Institute had certified seven homes in the U.S., with about a half-dozen others awaiting certification. In Colorado, an Austria-born engineer and developer, Norbert Klebl, has raised enough private equity financing to begin construction on the first phase of what he hopes will become a 250- to 280-unit enclave of passive houses. Klebl said in October that the first six houses, which are presold, will be built within Geos, a master planned net zero-energy community in Arvada, Colo. Klebl says the passive houses would range from 1,000 to 2,200 square feet, and sell for between $230 to $250 per square foot. Construction is slated to start in January, and Klebl says there’s a waiting list for the next 15 units.
Willamette Week Online reports there are 10 passive houses under development in Oregon alone. But Milos Jovanovic, founder of Root Design Build in Portland, Ore., which this summer began construction of its 1,741-square-foot passive “Shift House” in Hood River, Ore., tells Builder that some required materials still aren’t available from U.S. suppliers. He adds that the Institute’s literature is still in metric measurements and only recently had been translated into English. (Moore says a more accessible English-language manual “is in the works.”)
Moore believes that as American builders and architects become better acquainted with passive construction, they will introduce architectural and design elements these boxy houses so far have lacked. “The shape of the building doesn’t really matter,” asserts Nahib Tahan, an architect and owner of Bau Technologies in San Rafael, Calif.
Last year, Tahan remodeled a 100-year-old house in Berkeley, Calif., to passive standards. That required lifting the first floor by 3 feet, installing a new foundation, and gutting the first and second floors. All told, the 1,500-square-foot project cost about $300,000. (Root Design Build has budgeted $330,000 for Shift House; Wright spent $367,000 to build his.) Builders acknowledge that re-education is needed to help home buyers see beyond a passive home’s selling price, design, and heating methods, and appreciate its energy-saving benefits.
Tahan thinks “a new name and a different perspective” might help to market this concept in the U.S.. He also believes passive construction would gain immeasurably if green building standards such as LEED focused more on measuring energy consumption.