Since August, commuters on West Lake Sammamish Parkway S.E. in Bellevue have noticed a major distraction on the east side of the road. Workers climbing up and down the steep hillside — roped off like mountain-climbers — and cranes lowering concrete slabs into place. There were tall stacks of panels that looked like Styrofoam-and-wood sandwiches and compost was being blown into mesh tubes.
In short, this is not a typical homebuilding site. Puzzled passers-by were witnessing the creation of a new kind of home that’s expected to be a model of high-performance and energy-efficient construction. Dubbed the Zero Energy Idea House, it’s being built by Issaquah-based Shirey Contracting. Owners Donna and Riley Shirey, who will live in the home when it’s finished, decided to open the construction process and the completed home to the public to teach people about how homebuilding is changing to meet new environmental challenges and goals.
Challenge #1: You Want to Build Where?
As the region’s population continues to grow, finding places to build new homes is becoming more difficult. The site for this home is on a very steep slope above Lake Sammamish and is classified as a “critical area” by the City of Bellevue.
“Our project is one of the first to meet the city’s newly adopted Critical Areas Ordinance,” project architect David Clinkston said. “The ordinance places strict limitations on development in environmentally sensitive areas and required us to get a Critical Areas permit in addition to the building permit.” In order to meet the Critical Areas stringent requirements, the Shireys and Clinkston worked with a “who’s who” of site experts, including geotechnical, civil and structural engineers, a land use planner, a wildlife biologist, a certified arborist, an erosion-control specialist and two landscape architects. In the end, not only was the permit granted, but the city stated the site would be more stable with this house on it than it was before.
Challenge #2: Not Slip, Sliding Away
In August, work began. Sickly trees were identified and carefully removed. Non-native vegetation was cleared by an intrepid team of landscapers from Frog on a Log Parks of Everett. They repelled down the slope with climbing gear. Then the next goal: keeping things from sliding downhill during construction, especially during rainstorms.
Cedar Grove Construction Services of Seattle, known mostly as a garden compost producer, worked with the builders to use compost to help prevent erosion at the site. They sprayed a 2 inch layer of compost, called a blanket, across the entire slope. Then filter socks, which are mesh tubes filled with compost, were laid across the slope every 50 feet to help absorb heavy rain.
“The socks we used on this project are biodegradable,” Cedar Grove’s erosion control specialist Jami Burke said. “They’ll become part of the landscaping at the end of the project and continue to protect the slope.”
Many other decisions about the project were driven by the need to keep the slope stable. The house sits on a series of deep, auger cast piles and six interconnected grade beams that keep it firmly anchored to the site, with soldier piles providing additional shoring for the adjacent roadbed. “All in all, we used 28,000 pounds — 14 tons — of rebar,” Donna Shirey said. “That house isn’t going anywhere!”
Challenge #3: Growing a Green Building
Like all new construction, the Zero Energy Idea House displaces existing vegetation which was merrily going about its job of converting tailpipe exhaust and other pollutants into oxygen. Was it possible, the Shireys wondered, to incorporate vegetation into the structure of their new home to make up for the vegetation they were removing to build their home?
One answer came in the form of a green roof. Designed by landscape architect David Hilgers of Triad Associates of Kirkland, the top of the Shireys’ new home will feature more than 1,000 square feet of vegetation, planted in 2-foot by 4-foot trays for easy maintenance. The plants started growing almost a year ago so they’d be ready. Although the plants were selected for the location, they’ve been provided a drip irrigation system that draws from the home’s 3,000-gallon rainwater cistern.
The roof isn’t the only part of the house that’s made of vegetation: the north side features a “living wall.” This isn’t just a mound of dirt and plants: it’s a structurally engineered installation that combines compost (in those filter socks again) with special netting for reinforcement. Add plants, and you’ve got an attractive alternative to a concrete or masonry retaining wall that also absorbs storm water and produces oxygen. As the plants grow, their root systems will make the wall even stronger.
Challenge #4: Less Wood, More Insulation
Wood does a lousy job of insulating a house, and the typical home leaks energy everywhere there’s a stud in the wall. Traditional batt insulation leaves gaps that make the situation worse. Builders shooting for “zero energy” are on the lookout for better ways to build a wall.
Shirey Contracting has been using one such method, structural insulated panels, or SIPs, for more than 20 years. “I like to call it smart building,” says chief operations officer Riley Shirey. “Reducing energy use starts with the exterior walls, floor and roof — what we call the thermal envelope. With SIPs you get a strong, fully insulated structure that’s almost airtight.”
SIPs feature expanded polystyrene (EPS) foam sandwiched between sheets of OSB, engineered wood paneling made from small pieces of sustainable fast-growing trees. Detailed house plans are sent to the SIPs manufacturer, in this case Insulspan in British Columbia, Canada, and what comes back is a collection of custom-made panels labeled for easy installation. Window and door openings are already cut, and tunnels called chases are pre-drilled for electrical wiring.
The tightness of SIP buildings raises red flags for some people, but it shouldn’t, says Insulspan representative and architect Steve Sullivan. “Building a very tight home like this one gives the owners the ability to totally manage their indoor air quality with mechanical ventilation,” Sullivan explains. “You want to control the air movement, not have it leak out carrying heat or allow pollutants to seep in from the garage.”
SIPs also have the advantage of speeding up the construction process. Shirey’s crew had the first floor of the home complete just three working days after the panels were delivered — framed, insulated, and sheathed with OSB, all in one step. Because the panels are custom made for each project, there’s also no waste.
Another “better way to build” is with insulated concrete forms, or ICFs. ICFs use EPS foam, too, but this time it’s on the outside, with concrete poured in the middle after rebar has been inserted for reinforcement. The result is a strong foundation wall that uses less concrete and is fully insulated.
With low-impact development, a stable foundation and a well-insulated, tight building envelope, the Zero Energy Idea House is well on its way toward meeting its ambitious goals. In the next Zero Energy Idea Home article, we’ll look at the appliances, lighting, and other products inside.
Pam Worner owns and operates Green Dog Enterprises, Inc., and is the green building and marketing consultant for this project. She is also a freelance writer.
See our other Idea House stories:
East meets West (Sept/Oct 2012)
Home Green Home (January/February 2010)
Mid-Century Modern Masterpiece: Inside the 425 Idea House
Elegant Meets Rustic: Inside 425′s Coal Train Cabin
Finishing Touches: Picking Products for a Resort Home
Healthy Home: A Snoqualmie Family Goes Green
Seeing Green: Cutting-Edge Products in Bellevue’s Zero Energy Idea House (May/June 2009)
Close to Home, Yet Far Away: Second Homes at Suncadia are Drawing People East (July/August 2008)