The "Boussoleil" Home Integrates Solar, Geothermal, and Water

"I am inspired by the delicious dialog that can arise between a home and its place," says architect François Lévy. He coaxed out such a dialog for clients Nancy Newell and Joerg Becker when he designed their sustainable, aging-in-place retirement home on a 16-acre rural site near Elgin, Texas.

Called Boussoleil – "which is a made-up French word meaning 'sun compass,'" he says—the solar-powered, all-electric home has a geothermal wellfield and harvests its water from the rain. "Sustainability is in our blood," says Becker. "I grew up in Germany where there's such an emphasis on recycling and sustainability in general. These are values that have stayed with me and formed over the years." Adds Newell: "I've always had a connection to the earth and want to be a good caretaker of it."

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Fully Integrated Systems 

After raising a large blended family in Austin, the couple wanted a sustainable home that would be super energy-efficient, low-maintenance, and adaptable to aging-in-place. They also wanted a design that would suit their modern sensibility, "while remaining sympathetic to the land and sensitive to nature," Lévy says.

The couple knew Lévy through a class Becker had taken with the architect on Vectorworks, a BIM (building information management) program for architecture, c, and stage/event design. Lévy is also the author of BIM in Small-Scale Sustainable Design.

"As we were deciding on our design, we started with our needs and wants," says Newell. "No steps, wheelchair access to the outdoors from the master suite, solar power. We want to retire here. A colleague of François's found a builder who fully integrates solar, rainwater, and geothermal in their house. We liked that idea. François included all of that our house."

Lévy believes that solar orientation, prevailing winds, vegetation (its scale and patterning), the site's topography, and the context of nearby natural and human-made features all inform a residential project. "Buildings that are responsive to their place," he says, "not only perform better, but are beautiful and satisfying—not because they parrot the mere form of natural structures, but because they are deeply absorbed in the laws of natural systems."

How Did the Project Achieve Optimal Sun/Shade and Systems Balance?

First, Lévy sited the house for optimal sun and shade. With its dominant east-west axis, the home maximizes solar while allowing the nearby trees to remain. Lévy used Vectorworks throughout the design, documentation, and construction of the 2,500 square-foot home. He did studies during the early design iterations to balance optimal shading and photovoltaic collection while minimizing site disruption. He balanced south-facing glass to internal exposed thermal mass (concrete floors and masonry fireplace surround) for winter passive solar heating. He designed a thermal chimney, which the homeowners call "the shark fin," for a stack effect: a natural ventilation strategy.

"The shark fin was one of François's ideas," Becker says. During summer months, "we open the windows on top and hot air escapes. It works well."

Lévy estimated the chimney's effectiveness using established ASHRAE formulas and data provided by the model's geometry. Lévy also created a "rainwater harvesting tool" for the project—a spreadsheet with the home's proposed roof and garden areas—to calculate the optimal cistern size: 20,000-gallons. 

What Sustainable Details Did the Project Implement?

Completed in June 2014, the wood-frame home has eight inches of spray foam insulation in the roof and six inches in the walls. The exposed concrete floors are slab-on grade. Standing-seam metal covers the roof and the walls. "When we were designing the house, there were lots of fires in the area, and ash was falling everywhere," Newell says. "We were looking at not only safety but also low-maintenance materials" when choosing the exterior cladding and roofing for the house. 

The roof-top solar array includes 31 panels. "We're grid-tied," explains Becker, "which means when we produce power during the day that we don't need, we send it into the grid and at night pull it back in."  The geothermal system includes four wells 150-feet-deep, "which go into a system and precool the incoming air from the outdoors," Becker says.  

In addition to the "shark fin," a smoke hood over the electric stove pulls our heat. "A slot in the ceiling opens up to let out that excess heat," Becker says.

The couple collects nearly all of their rainwater from the roof, which is stored in a tank. An on-demand pump brings the water into the house, where it's cleaned, and UV filtered. "We use rainwater for all of our drinking water, showering, dishwashing, etc.," Newell says. "Every drought, we sweat. Usually, it's enough water for us, but it's not enough to also water the plants when it's dry. We put in a municipal pipe, so we don't lose our vegetable gardens."

Looking Forward, Looking Back 

Inside the home, the walls are drywall and acoustic wood. Most of the couples' furniture is bamboo. Fiberglass windows and doors let in abundant natural light. "We enjoy delightful light in the house," Newell exclaims. "We have walls of windows on both sides of the house." The windows and sliding glass doors provide natural ventilation in the air-tight house. "We can get a lovely cross breeze very readily any time of year," Newell says.

Having lived in the house for several years, is there anything they would have done differently? "The master bedroom is too big," says Becker, "and looking back, we could have made one of our guest rooms slighting bigger. We don't have much storage space, which is great because that keeps us from hoarding stuff, but it can be a challenge at times." The couple also would have chosen "one grade higher windows, because these are starting to look worn," Newell says.

Overall, however, they couldn't be more delighted with their home. "The foyer with the shark fin is a lovely feature," Newell explains. "We have glass-block walls, and when the full moon comes up, it illuminates the house with a rippled light effect. It's magical."

The open-plan living area, with its nine- to 17-foot ceilings, "remains very stable in temperature," Becker adds. "We use ceiling fans when the room starts to feel warm, but it never gets hot, and during a winter storm, when we didn't have electricity, the house stayed at a comfortable 60 degrees."

The aviary is now a screen porch where the couple enjoys eating breakfast and watching thunderstorms. Moreover, Becker adds, "We have the best water in town."

Article by:

Camille LeFevre

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