“They say you cut your teeth designing and building your first Passive House,” said Marie Ljubojevic, a lead project designer for NK Architects. Bringing the first such house to Seattle was an exercise in experimentation, troubleshooting, and, of course, creativity, Ljubojevic added.
The rigorous energy efficiency guidelines for designing and building a Passive House are set by the Passivhaus Institut in Germany and its U.S. arm, the Passive House Academy. One BTU per square foot per heating degree is required in the U.S.
The first-ever Passive House project, four row houses, was built in 1990 in Darmstadt, Germany. Since then, while over 25,000 buildings have integrated passive house standards in Europe, numbers in the U.S. are significantly less, in the low hundreds. But the method is starting to take hold.
In Seattle, designing and building Park Passive in the Madison Park neighborhood presented an array of challenges, particularly on a constrictive urban lot, approximately 30 feet deep and 65 feet wide.
The firm almost tripled the former home’s square footage to 2,710 square feet and raised the roof five feet higher. The single family home has three levels, with four bedrooms and three baths. The lot constraint of shallow and wide was a harder configuration to work with but ultimately a smarter way of interpreting the lot to prevent heat loss issues, Ljubojevic explained.
Minimizing energy requirements is a central goal, through passive solar gains, super insulation, and airtightness. Park Passive uses 90 percent less energy for heating. “We used triple glazed doors and windows,” said Ritchie, as he turned to demonstrate the lift and slide system that ensures an airtight seal on the sliding glass doors in the main living area on the ground level.
Shallow floor plates necessitated an emphasis on vertical space. The home is airy, light-filled, and white-walled. The open kitchen layout, which features blonde oak cabinets and concrete flooring, is oriented toward the living space, fronting a patio landscaped by Allworth Design. Double vaulted ceilings merge the kids’ play area on the second level. In the first floor bathroom, a living edge countertop was harvested from an ash tree on the property, which was also salvaged to create stair treads, a children’s sized bench in the light-lit stairway, and wall paneling.
Because of the home’s extensive insulation, ventilation is key. Walls are approximately 16 inches thick, double insulated with dense pack fiberglass with air sealing in between. Tilt and turn windows in the bedrooms and skylights on the third floor bring in fresh air, while a heat recovery ventilator ensures adequate airflow during the cooler months.
Undoubtedly, the coolest part is the roof deck, with views of the Cascade Mountains and Lake Washington. It is a green oasis, with planter beds of grasses arranged in neat rows along the corner and even some homegrown vegetables. And there is a hot tub.
Building in the famously wet northwest winter “required advanced thinking through the details,” said Ljubojevic, “and a customized and rationalized approach,” added homeowner and builder Sloan Ritchie. In a house that is so well insulated that moisture cannot escape easily, the team had to drill over 50 holes to let humidity out from the interior. They took photos with an infrared camera as visual proof. “Ensuring the structure and the air barrier worked together was one of the most challenging parts,” Ritchie told me.
Ritchie and his family moved into the home this April, so they haven’t needed to use the heat yet. But Ritchie said it passed all of its tests and the home is performing well.