©2013 Green Building Advisor. From The Taunton Press, Inc., publisher of Fine Homebuilding Magazine.
A house built into the side of a Virginia hillside on a working water buffalo farm has been named the outstanding single-family home of the year in the 2013 LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. Awards by the U.S. Green Building Council.
"Earthship Farmstead" in the western Virginia town of Stuart, was one of seven projects  recognized last month by the U.S. Green Building Council. It was designed by Kaplan Thompson Architects  of Portland, Maine. (Jesse Thompson, the lead architect on the project, is partnered at the firm with Phil Kaplan of GBAGreenBuildingAdvisor.com's Green Architects' Lounge .) The house was built by Structures Design/Build.
The 3,600-sq. ft. house, which was completed in 2012, includes three bedrooms and an outside terrace nearly as big as the house itself. It meets both the PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. and LEED Platinum standards, the USGBC says. "Earthship Farmstead," Thompson said, is a reference to the New Mexico Earthships of Michael Reynolds .
According to an article about the house appearing in the Wall Street Journal's "Mansion" section on May 9, the house was built for David and Liisa Wallace, an English couple who had wanted to leave the Britain and found the 104-acre parcel in rural Patrick County with the help of Ms. Wallace's brother.
The Wallaces wanted a house that disappeared into the landscape, and when viewed from atop its sod roof that's more ore less what they got. But Thompson said building this insulated, underground structure capable of meeting the Passivhaus standard was very complex. "It got complicated," he said.
To comply with the Wallaces' request for a roof where sheep could graze, Kaplan Thompson used Lite-Deck  steel-reinforced EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest. panels as a base and then poured a concrete cap that is 8 to 10 inches thick on top of them. The concrete is waterproofed with a fluid-applied membrane made by Carlisle . All of that is insulated with 4 inches of termite-treated EPS rigid insulation, followed by 18 inches of earth.
The Carlisle membrane is protected by an embedded electric field, Thompson said, that can be used to test for leaks over the lifetime of the house. The technology is used in structures such as parking garages to pinpoint leaks in places that can't be inspected visually.
Although the Wallaces didn't say how much the house cost in total, David Wallace said the roof alone was several hundred thousand dollars, the WSJ reported. It should, however, last for 50 years or more, Thompson said, in part because the steel-reinforced concrete is thermally stable and not subject to freeze-thaw cycles.
And as to the couple's wish to graze their farm animals on the roof, Thompson said engineers nixed the idea.
"The engineer said no, no cows," Thompson said by telephone. "They mostly worried about the punching loads of the hooves and the waterproofing, so they said, ‘Please, don't actually put cows and sheep on the roof.’ " (The cow standing on the roof in the photo at the firm's website is there courtesty of Photoshop).
Another challenge was getting enough direct solar gain from a building site that faces east. Portions of the building are underground, but Thompson brought some of the structure away from the hillside and installed large south-facing windows to pull in winter sunlight, a description of the project on the firm's website says.
Because the house is designed to meet the German Passivhaus building standard, Kaplan Thompson says it will use 90% less energy for heating than a conventionally built house and will have a heating budget of roughly $500 a year.
Other features listed by Kaplan Thompson:
Thompson said the Wallaces were completely uninterested in building a conventional, wood-framed house, and drawn instead to a structure more in keeping with their European roots.
"It's not inexpensive to build like this," he said. "They wanted a very nice house that also had these technical features. That was one of their prime goals. You're building a very tough concrete structure; it's not how American houses are usually built.
"They thought American homes were far too flimsy," he continued, "and they said, 'We are not having an American 2x4 or 2x6 house where you could put your fists through the walls. We are not doing that kind of house. We want a tough house. We want a house like we would expect at home."