One inspiration for a Passivhaus project that recently broke in Bethesda, Maryland, just outside Washington, D.C.’s northwest border, was a wintertime visit by builder Brendan O’Neill and his son, Brendan Jr., to a home in Illinois that had been constructed to Passive House standards. The visit, as noted in an announcement about the Bethesda project, happened to occur during a blizzard.

“It was as toasty and comfortable as any house I’d ever been in,” the senior O’Neill recalled. “I looked in the mechanical room and the little heat pump was barely even running. I turned to Brendan Jr. and said, ‘We’ve got to build one of these.’”

O’Neill followed through on the comment. The O’Neills’ company, O’Neill Development, partnered with another firm that operates primarily in the D.C. area, Peabody Architects, to design and build the house in Bethesda.

As Passivhaus residential projects go, this one is bigger and, in part because of home’s high-end location and the amenities planned for its interior, considerably more expensive than most. It will include five bedrooms and four and a half baths. The area, for the purpose of Passive House Planning Package modeling, is about 3,600 square feet, although David Peabody, principal of Peabody Architects, notes that the true size of the building, including a finished basement and attic, will be 4,318 square feet. The listing price: $1,688,000.

Digging into details, enjoying a confidence boost

Peabody says the building will have an R-62 roof, R-42 exterior walls, and an R-20 slab. The roof, in fact, is expected to be in place by the end of this week, barring a prolonged bout of wet weather. The hot-water heater is equipped with a heat exchanger, and hookups for both solar hot water panels and solar power panels have been run to the roof. The plan is to let the eventual homeowner install panels, Peabody adds, “as they get them at 30 cents on the dollar due to tax incentives and we don’t. Same with PV hookups.”

The project broke ground on August 23 and has progressed reasonably quickly so far, although the focus on insulation and airtightness has been predictably intense. At one point last month, though, after gravel was poured and prepped, foam tiles were laid down, tightly fitted, and covered with 15 mm polyethylene Stego Wrap whose seams were then thoroughly taped, the job site got a surprise visit from Katrin Klingenberg, director of Passive House Institute U.S. Klingenberg was in the D.C. area for one of the institute’s training courses.

“Of all days Katrin could have come, this was the best,” the project team noted on a blog site, Passive House DC, that tracks the building’s construction. “It was a first for all of us at taking these extra steps of sealing, and having her go over our work and pronounce it first rate before the concrete went in gave us all a big boost.”

The project’s partners expect the house to be completed in the spring of next year.