Introducing workforce homes for $80,000 to $150,000 in an area where the median home price is $684,000 is tough enough to engineer financially. On top of that, the Lopez Community Land Trust (LCLT) decided that Common Ground, its fourth affordable pocket community on an island 80 miles north of Seattle, would be self-sustaining from an energy standpoint.

Executing that decision was the tricky part. Given the climate, the project team determined that energy usage on the site—which was slated to include 11 cottages, two studio apartments, and a small office—could be reduced by 48 percent through passive measures. The remaining power needs would have to be recouped through renewable energy production.

Straw bale and earthen plaster were locally available and became the primary ingredients on the conservation side. Using 18-inch straw bales as building blocks rendered insulation values between R-35 and R-43 and, combined with blown-in cellulose R-50 insulation and fiberglass windows, produced a pretty tight shell for each little house. South-facing windows were specified to capture the sun’s warmth, while the north elevations were padded with extra insulation to keep out the cold. All of the homes have solar hot-water systems, timed fans for ventilation, low-flow plumbing fixtures, and high-efficiency lighting.

An ultra-tight budget required trade-offs, including resistance heating instead of high-efficiency heat pumps. “This wasn’t the most efficient option, but it allowed us to spend only a few hundred dollars per house on electrical units,” explains LCLT executive director Sandy Bishop. “We knew we could get away with it since we were insulating the windows and walls to use as little energy as possible.”

How residents would live in their homes was also a big consideration. “We focused on making these homes as low-tech as possible so users wouldn’t have to worry about technical gadgets that might malfunction,” explains Tammie Schacher, a principal with Mithun, which provided architectural design and land planning. “We followed the age-old rules of passive solar design, harnessing the sun for warmth and breezes for cooling and air exchange.”

Net Zero Housing

Technology outside of the house was another matter. A 300-foot photovoltaic array on the southern end of the site is the main power generator for the neighborhood, and a 38,000-gallon rainwater catchment tank collects and recirculates graywater for washing machines, toilets, and irrigation. Conduit for an eventual wind generator has already been laid.

The residents of Common Ground—including a teacher, a construction worker, and several small-business owners—moved in roughly a year ago. “Each homeowner has an energy manual that explains … when to lower the sun shades, when to open or close windows, and how to keep the indoor temperature as even as possible,” says Schacher. Each home also contains an energy meter to help residents track their usage patterns.

“We can design as best we can, but in the end, [it all] depends on user behavior,” she adds. “The person who lives in the house has to be as enthusiastic about energy conservation as the architect and builder. And they have to control their consumption accordingly. We call it the last mile.”

Learn more about markets featured in this article: Seattle, WA.