“It didn’t merit saving.” So remembers Lauren McCunney of NK Architects about a dilapidated cottage in Seattle’s eclectic Madison Park neighborhood. Yet this former rental had one very important feature going for it: Sitting only 2 feet from the rear property line, it did not conform to the city’s zoning envelope. Thanks to the grandfathered condition, McCunney and NK’s Marie Ljubojevic were able to construct a 3-story, 2,710-square-foot building on the 30-foot-deep site, which also measures 66 feet wide.
Photo © Aaron Leitz
“The client had a pretty demanding program for the size of the lot,” McCunney says of the homeowners, public relations executive Jennifer Karkar Ritchie and her husband Sloan Ritchie, whose sustainability-focused company Cascade Built fabricated the house. “The house would have been 14 and a half feet deep without using that existing portion.”
Another demanding criterion: The four-bedroom, three-bath home is Seattle’s first to earn Passive House certification. It also is the first successful Passive House project for NK and Cascade Built, both of whom credit the collaboration between design and construction teams for the achievement. In the spirit of sharing knowledge, the Ritchies are occupying the new home, in part so that Sloan can impart his firsthand experience of Passive House to Cascade Built’s queue of future work.
The project commenced in summer 2011. To take advantage of its zoning variance, NK rebuilt the form of the cottage on the backside of the house, which faces south, and added five feet to the roofline overall. On this dense corner of Madison Park, surrounding development complicated solar exposure and privacy on the rear elevation. So large windows were installed on the third floor for solar gain; operable skylights do the same, and account for stack ventilation. Upstairs, large east- and west-facing openings make the bedrooms feel larger. All the windows are triple-glazed Intus products.
Fenestrating the north, the public face of the house posed a slightly different problem. “Because the house has no backyard, our strategy was to open the house to the front yard and make the living space feel much larger on the first floor,” McCunney says, and now a combination kitchen-living room is separated from a screened front patio by an expansive sliding door. “Yet Passive House in a climate like Seattle really wants to limit north-facing windows, and opening the front space to the yard in this way required a steel header that’s a thermal bridge. You have to have a tradeoff somewhere else.” NK decided that that “somewhere else” would be the roof, whose 89.3 R-value is the result of an insulated joist topped in rigid polyisocyanurate insulation.
Walls are approximately 17 inches thick. An insulation wall formed with TJI joists hangs outside the 2-by-6 structural wall, and the sheathing panel installed beyond that serves as the mount for the house’s corrugated metal siding. A heat recovery ventilator provides continual fresh air year round.
NK confronted forks in the road beyond the steel header. Since it had to organize the building vertically to achieve the desired square footage, for example, it transformed the stair into an asset, expressing it in fiber cement board on the exterior and placing windows at various heights to make its landings enjoyable for both the homeowners and their children. A mature ash tree had to be taken down to build the bigger house, but now its wood clads the stairwell interior and comprises its treads. These and other decisions affect neither the Ritchies’ lifestyle nor their eco-performance as the house consumes as much as 80 percent less energy than comparable code-built new construction.
“You can design a Passive House as a box with punched openings that performs perfectly for your energy modeling,” McCunney says of the tradeoffs theme, “but for architecture to be truly sustainable, it has to be livable and pleasant, too.” Armed with this more nuanced understanding of high-performing residential building, NK, like Cascade Built, is applying its Passive House wisdom to additional, as well as larger-scale, residential efforts.