Is Northern Virginia becoming an incubator for innovative environmental housing? We’ve got the tiny house, the new green neighborhood in Centreville and now in Falls Church the first “passive house” is under construction and passed its first test with more than flying colors.
A “passive house” uses 90 percent less energy than conventional houses, in part by using heavy insulation and airtight seals to maintain internal temperature without the external fluctuations of silly things like “seasons” and ”extreme weather.” The first one in Northern Virginia was built in Arlington, and now Nelson and Caroline Labbe are building one in the Pimmit Hills neighborhood of Fairfax County, with the help of architect Peter Henry and builder Richard Dobson.
The house has to be carefully built at every stage, including placing foam insulation under the concrete slab and around the footers. It’s not necessarily cheap, yet — more than $600,000 for this 3,000-square foot, four-bedroom house. But when an external energy monitoring firm came in to examine its efficiency so far, their numbers for a first test were “superb,” said Richard Lensis of Energy Masters. An average house has 10 to 12 air exchanges per hour. The Labbe house had less than half of one air exchange.
The first passive homes were built in Germany in 1990, and there are thought to be about 20,000 “passivhaus” units in the world, mostly in Europe. In the D.C, area, there are four: One in Arlington, one in Bethesda and one in Northeast Washington that was a
State University of New York joint New School and Stevens Institute of Technology student project for the Energy Department’s biennial Solar Decathlon on the Mall.
By insulating and sealing the house, it becomes much more energy efficient by not having to heat or cool itself to contend with the exterior elements. In Pimmit Hills, the Labbes’ house not only has insulation under the slab, but two feet of insulation in the attic, and two inches of foam insulation on the exterior walls, which are already 9 1/2 inches thick. The insulation is also treated to fend off termites and permit drainage.
The windows are triple-paned. Rubber gasketing is used at all frame junctions. The doors all have three latches, for tighter seals. Three-foot overhangs shade the house from too much heat, and the south wall features large windows. The studs in the frame, which Henry said are a major source of energy loss, are two feet apart instead of 16 inches, and are lined up floor to ceiling.
“We’ve been building houses the same way for 150 years,” Henry said, from the days of wood-burning heat stoves to central air and heat furnaces. “There hasn’t been much thinking about thermal efficiency.”
Labbe, who works for the U.S. Army Corps of Engineers, said his colleagues work on energy conservation, and it convinced him and his wife they wanted to build an energy efficient house. “We learned about passive houses,” Labbe said, “and we thought, ‘that’s it.’”
An active kayaker, Labbe mentioned his interest in a passive house to another kayaker, Henry, not knowing Henry was an environmentally involved architect. Henry took training from the Passive House Institute U.S. and worked with the Labbes within their budget.
The Labbes found a bank willing to finance them, Sandy Spring Bank, on their second try. “We explained it to them, and they said OK,” Labbe said.
Just as important as having a knowledgable architect (and a willing bank) is a capable conscientious builder. The Labbes hired Dobson Building and Remodeling. Rick Dobson said the job was “just a little more time-consuming, with a much greater attention to detail. But it’s not that big of a jump for us because we’re custom home builders.”
Eric Kluge, the project manager, said the Pimmit Hills house will be a helpful experience. If they do another passive house, “our efficiency’s going to pick up,” Kluge said.
The passive house will use no gas or any combustion devices, which require outside ventilation. Instead, all the ventilation is controlled and 90 percent of the air that passes through the house will be recycled through an Energy Recovery Ventilator, Henry said. Two “mini-split” units, small self-contained devices, will heat and cool the air without taking up the room of a central furnace.
Vapor barriers are built in to keep moisture from building up inside, and the mini-split units can also function as dehumidifiers, Henry said. Water will be heated with a heat pump. The stove will be a low-energy induction stove. All lights will be LED or CFL.
The annual energy costs for the house should drop from about $2,000 for a 3,000-square foot to about $200 a year, Labbe estimated.
That’s if it remains super efficient. Its first test came in September. Lensis said he’d never seen a house pass on the first try. He explained that a standard house has air entering and leaving through the equivalent of a 2-foot by 2-foot hole, and so air changes 10 to 12 times in an hour. The Labbe house had the equivalent of a half-inch hole, and half of one air change.
“The architect had a really great design,” Lensis said. “They took special care to seal the envelope up, and the builder did a fantastic job.”
But he cautioned that the task isn’t completed. Now that electrical and plumbing contractors have been in, drilling their holes in the house, a second test will be run before siding and other permanent external touches are applied. Then, a third test will be done after the house is finished for final certification.
Construction started in May, and Dobson said he hopes to be done by late January or early February. The house is larger than most in the Pimmit Hills neighborhood, but not conspicuously so. If the house is certified, Labbe said he will allow tours from around the world to inspect his working passive house.
CORRECTION: One of the existing passive houses in our area was originally misidentified as being constructed by students from the State University of New York. It was built by students in a joint project between The New School of New York and Stevens Institute of Technology in Hoboken, N.J.