Park Passive: Seattle’s First Passive House

"Jokingly, we tell people we plan to heat the house with a hairdryer," said Sloan Ritchie in 2013. The founder and president of Cascade Built in Seattle, Ritchie and his wife Jennifer Karkar Ritchie, CEO of Revolution PR (a sustainable lifestyle public relations agency), were excited to complete and move into their new home, the first Passive House in Seattle. On Cascade Built's website, Ritchie added that the hairdryer reference represents the approximate heat required given their extreme attention to insulation, air sealing, and high-performance windows.  

Ritchie, a pioneer in Seattle's Passive House movement, works with building-science principles to guide the design and construction of buildings that use up to 80% less energy for heating and cooling. The Ritchies' home is one of Cascade Built's most energy-efficient projects. Designed by Nicholson Kovalchick Architects, the 2,710-square-foot, single-family home rises three levels on its 2,000-square-foot infill lot, which is closely bordered by a neighboring house to the south. The home meets PassivHaus Institut standards by reducing heating energy consumption by nearly 90%.

The couple chose to go with Passive House principles in building their home, says Karkar Ritchie, because Passive House "is the most effective way to reduce the impact of buildings on the environment. Buildings create more than one-quarter of all greenhouse gas emissions, according to the Global Alliance for Buildings and Construction. Passive House reduces consumption by up to 80%; plus, building to this standard creates a healthier and more comfortable environment for occupants."

The couple happily resides in the home with their two children and two fluffy cats. "We breathe filtered fresh air," she adds. "Our house is very quiet and more secure. It's also a consistent temperate 70-degrees without having to blast the heat in the winter."

Passive House Site Challenges 

In 2013, says Karkar Ritchie, the biggest challenge the team faced in designing and building a Passive House "was being the first. We worked with a design team that had never designed a Passive House and sub-contractors who had never built a Passive House building." Rob Harrison of Harrison Architects provided valuable assistance as the Passive House consultant.

The next biggest challenge, she adds, "was our lot orientation and lack of south-facing exposure." An existing house near the southern lot line posed a problem. The house needed a small, shallow floor plate. Zoning required the team to work within the existing house's form. Moreover, Passive House requires minimal glazing on the house's north side and 16-inch-thick walls.

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Those challenges led to creative solutions. The four-bedroom, three-bath home has a double-height vaulted kitchen that connects the main living area to an upstairs play area. The windows along the open stair bring in abundant daylight and street views (also seen from a window bench nook). The front façade features flared bay windows. The home has a roof deck with panoramic views of Lake Washington and the Cascade Range.

The home's clean, modern design is "as bold as the Passive House concept itself," Ritchie has said. As such, the home is a stellar example of how sustainability and high design can co-exist.

High-performance, Super-insulated

The slab-on-grade construction includes eight inches of high-density EPS foam under the footings, and another 20 inches of medium-density EPS under the slab to reach R-100. (Ritchie adds that most of the rigid foam under the slab acts as fill to raise the grade; it wasn't necessary to meet the home's Passive House goals.) The eight-inch layer of foam beneath the footings continues up the outside of the stem walls to connect with exterior wall insulation.

The exterior walls are comprised of a 2X6 structural wall, an OSB air barrier, and nine-and-a-1/2-inch deep I-joists with about 15 inches of blown-in fiberglass insulation. The walls are about R-60. The roof insulation combines 24 inches (or more) of blown-in fiberglass and four inches of polyisocyanurate insulation, resulting in R-100.

An initial blower-door test, conducted before windows or drywall were installed, clocked 0.4 air changes per hour. After the windows were installed, another test measured 0.5 ach50. 

Because the Ritchies' Passive House is built so tightly, mechanical ventilation is needed to keep the indoor air healthy and comfortable. A Zehnder ComfoAir 350 heat recovery ventilator brings in fresh air. It also works in conjunction with the Mitsubishi mini-split HVAC system to reduce heating and cooling requirements.

The operable Intus high-performance windows and doors can be opened and closed in summer. An AirGenerate AirTap heat pump water heater (no longer on the market) provides hot water. The house was also pre-wired for solar.

The couple clad the house in corrugated metal, cedar, and Silibonit fiber-cement siding. Inside, wood from a site-salvaged ash tree re-appears as stair treads, wall paneling, and a bathroom countertop. The ground floor has a concrete slab, while bamboo was used as flooring on the upper levels. The home used no-VOC finishes throughout.

Living Their Values 

Having lived in the home for several years, says Karkar Ritchie, there's little the family would have done differently. "We made a few modifications early on, including external shades to block solar gain in the summer," she says. "Now that the technology exists, we would have used a Sanden CO2 Hot Water and run it in the slab for heating."

The young family loves living in a modern Passive House that expresses their values. "We chose to build a Passive House home because it aligns with our values to do our part to preserve the environment for many generations to come. The energy savings, comfort, and healthier indoor attributes of Passive House are all added benefits." Simply put, she adds, "It's the right thing to do."

Article by:

Camille LeFevre

Camille LeFevre is an architecture and design writer based in the Twin Cities.