Jabe Blumenthal knows numbers. After graduating from Yale with a degree in Applied Mathematics he joined a little-known software company in the early 80s, Microsoft, and co-designed a little program we now know today as Microsoft Excel.
Jabe also knows climate change. He has served on the board of Seattle-based Climate Solutions for over a decade, advocating for ‘practical and profitable solutions to global warming’ throughout the Pacific Northwest. He also knows a thing or two about the costs and benefits of climate-friendly construction. He served on the board of the Bullitt Foundation when that group planned and built its noted “living building,” the Bullitt Center.
So when Jabe and his family began planning their new home in Seattle’s Madrona neighborhood, he was keen on finding a cost-effective path to low carbon building: a big bang for the buck investment. His research uncovered Passive House, an überefficient approach to construction that reduces heating and cooling energy consumption by as much as 90%. He then hired SHED Architecture & Design (project architect) and Hammer & Hand (project builder and Passive House consultant) to create his family home.
“We wanted a house that pushes the edges a little bit,” Jabe explains, “not the very bleeding edge of what is technically possible, no matter the cost, but on what’s almost economically reasonable today and should be quite reasonable tomorrow.”
“If the house costs ten, fifteen, or even twenty percent more to build in a climate-friendly way, then it’s reasonable for others with some extra money to replicate, especially if the 10th or 20th such house in Seattle costs only a few percent more. We want our house to be part of driving these technologies and building practices to be mainstream.”
To deliver on that goal, the project team simplified the home’s high performance wall assembly and built it using standard building practice. A 2x6 stud wall filled with 5.5” of high density fiberglass insulation provides a layer of thermal protection. Sheets of ZIP System sheathing, sealed at the seams with a simple-to-apply fluid sealant, provide structural integrity, airtightness, and weather resistance. A “winter coat” of 3.5” of ROXUL mineral wool insulation wraps the exterior, held in place by the fasteners for the home’s Forest Stewardship Council (FSC) certified cedar siding and rain screen battens. Just six layers of material make up the high performance assembly, providing a simple and replicable model for future Passive House projects.
Readily available systems and components round out the home’s high performance design. Triple-pane windows by Zola Windows optimize the capture of solar energy into the building while minimizing the escape of thermal energy out of it. During warm months, mechanical exterior shades block out unwanted solar gains, making a cooling system unnecessary. A Zehnder heat recovery ventilator delivers superior indoor air quality with a continuous supply of fresh air that recaptures heat (or cool) from outgoing “exhaust” air.
The home “pushes the envelope” in its heating and domestic hot water technology, pioneering the use of a Sanden heat pump water heater whose CO2-based refrigerant has a global warming potential (GWP) that is hundreds, even thousands, of times lower than conventional refrigerants.
The home’s Passive House design brings all these components and techniques together to make the house extremely energy efficient – so efficient that a relatively modest 9.8kW rooftop solar array will likely generate more energy than the house consumes on an annual basis: net positive energy. Jabe and his family will track progress to this goal with a circuit-by-circuit energy monitoring system equipped with a dashboard showing real time energy consumption and solar generation data.
So, Madrona Passive House is climate-friendly. Equally important, the home is a gracious place to live for Jabe’s family.
The home consists of three distinct levels connected by a central open stair, each level serving a specific purpose to meet the evolving needs of the family of four: the main level is shared living space; the upper level is the master suite, office, and exercise room; and the lower level is the dedicated kids’ quarters that will later be converted into an 800 SF accessory dwelling unit. SHED designed the main interior and exterior spaces to optimize solar exposure to the south while prioritizing an open connection to the expansive views to the east. Spaces requiring privacy and less natural light are arranged on the north side of the home to reduce glazing area and heat loss.
On the main floor, a restrained palette of FSC-certified walnut and ground concrete complement the natural green landscape visible through large windows and a floor-toceiling sliding door leading out to the deck. The built-in casework and kitchen cabinets (also FSC-certified) feature blue and green plastic laminate accents selected by the client for a fun splash of color. The upper level features FSC-certified walnut floors in a natural hard-wax oil finish, which circulate throughout the master bath, bedroom, exercise room, and office in a pattern that mimics the client’s daily routine. The lower floor features two ensuite bedrooms divided by a large rec room emptying out to the hillside with laundry and storage tucked behind the central stair. The flexible layout of this lower floor fits the current needs of the family and is equipped (pre-plumbed and wired for a kitchen) to evolve into a rentable one-bedroom flat in the future.
Madrona Passive House meets or exceeds all Passive House metrics, so both PHIUS+ Passive House certification and DOE Zero Energy Ready Home certification are expected soon. The project is also registered with the Living Building Challenge’s Net Zero Energy Building certification program, with certification anticipated after the requisite 12 months of energy data monitoring.
Meanwhile, Jabe and his family will enjoy the health, comfort, and efficiency of their net positive energy home, “powered” by Passive House design.