Having addressed the site logistics, the core team turned its attention to the plans for the 1,630-square-foot (conditioned space), 2-bedroom, 2.5-bath home. From the outset, all involved agreed that the exterior should exhibit as many green elements as possible. “We realized the site’s busy traffic location on the Sammamish Parkway presented an opportunity to tell much of the story even to drivers just passing by on the highway,” says Clinkston. “Things like the green roofs, a PV array, and a wind generator are all visible from the road and immediately identify this as an advanced-technology green home.”
Also visible is the metal grid around the front-entry vestibule, planted with vines that over time will grow to filter the afternoon sun and provide a shield from headlights at night.
That said, many of the home’s most important efficiency features aren’t immediately apparent, beginning with an R-22 Arxx ICF foundation.
The home’s roof, walls, and lower floors were all built using SIPs. The 6-inch-thick wall panels deliver an R-value of 24; the 10?1/2-inch-thick floor and roof offer R-40.
High-performance Ultra fiberglass windows from Milgard feature double-pane low-E glass and were flashed with VaproShield’s 3D to prevent moisture intrusion.
As part of their effort to get as close to net-zero as possible, the Shireys installed a 5.4-kW roof-mounted PV system made up of 24 SunPower modules, combined with a Helix 2.5-kW vertical-axis wind turbine; the jury is still out on the effectiveness of the turbine, given the short period of time it has been in operation.
The house features two hot water systems: A Unico UniChiller air-to-water heat pump delivers warm water for the Warmboard radiant floor system, and a Kingspan Thermomax evacuated-tube solar thermal system heats the domestic hot water supply, with a Navien tankless as a backup.
Like the rest of the project, when it came to finish product selections, the team researched every detail, even visiting manufacturers to confirm their choices. Interior finishes include zero-VOC Sherwin-Williams paint, locally grown alder trim with a water-based finish, locally crafted Pacific Crest cabinets, recycled-content tiles and countertops, salvaged wood floors, Energy Star appliances, and CFL and LED lighting.
In addition to rainwater collection and native plants, other water-saving details include dual-flush Kohler toilets, low-flow bath faucets, and rainfall-monitoring irrigation equipment.
But no matter how many green products and technologies the house contains, much of its efficiency comes from basic design fundamentals. “Living with less square footage and a fairly rectangular floor plan also affects energy costs,” Clinkston says. “When you have lots of bumps and jogs in a house, it adds more exterior walls and more area for heat loss.”
The Shireys, who now live in the house, see the project as a culmination of the knowledge they have garnered over the years about sustainability and energy-efficient materials. And, in the spirit of the project, the couple have opened the house up to the public for tours and educational events to spread the word.
Mindy Pantiel is a freelance writer in Boulder, Colo.