Location Thaxton, Va.
Architect/Designer/Builder/Passive House Consultant Structures Design/Build, Roanoke, Va.
Project Size 1,808 square feet
Lot Size 20 acres
Price $145 per square foot
Passive House may not yet be a household name in the U.S., but the European-born, ultra–energy-efficient approach to building is making inroads here, and some of the credit must go to Adam Cohen. Founder of Roanoke, Va.–based Structures Design/Build and one of the country’s first Certified Passive House Consultants, the architect teaches the Passive House Institute US course for builders, the curriculum for which he co-wrote. But his goal is to do more than train 180 new Passive House builders a year.
No Training Required
Cohen’s Passive package includes the elements to build a fully insulated foundation and shell. On-site advice from his staff makes specialized training superfluous. Heavily insulated and air-sealed foundations are key. Cohen has developed modular components that are cost-competitive with poured-in-place foundations. “The system is so simple that if you can set a wall panel, we can show you how to set a panel in an airtight way,” he says.
Delivery Included
Parts are delivered to the site. The package includes super–energy-efficient tilt-turn windows from Ireland but omits conventional materials, such as floor framing and roof trusses, which can be sourced locally. “All we do is the specialized Passive House stuff,” Cohen says. “Everything you can buy off the shelf, you buy off the shelf.” The system, he adds, is “modular, repeatable, standardized, and simple. And there’s no special training required.”
“It’s to change the way we build,” he says. To speed up the adoption process, Cohen has developed a modular design/build system aimed at making Passive House accessible to any builder—no training required—and at a cost that’s competitive with conventional construction.
Cohen combined software-based architectural design with panelized construction to make a “simple snap-together system.” An architect or designer creates a design using a set of modules: wall panels in 2-foot-length increments and with two plate-height options; building corners; six windows that can be ganged in varied ways; and three door types. Limiting the design palette greatly reduces costs, making it ideal for multifamily and production work, Cohen says.
Once a design is finalized, components are fabricated at the two factories with which Cohen has contracted. Wall panels consist of a 2x4 frame, insulated, sheathed, air-sealed, and covered with 6 inches of additional rigid insulation. To produce a building envelope that will meet the Passive House standard of 0.6 air changes per hour at 50 Pa of pressure, panels are joined on site with an expanding foam gasket (for vertical connections) and liquid-applied sealant (for horizontal joints).
When fully deployed, Cohen says, the system allows any competent builder to construct houses that meet the highest standards of energy efficiency and indoor air quality.
Cohen and his crew finished their first factory-fabricated project this past spring. Three more are scheduled for completion early this year, and Cohen plans to market the system to architects and builders later in the year. “We needed to do it because people were afraid of [Passive House],” he says. “This takes away a lot of the uncertainty.”
