Claudia Schneider was good to the earth, and in return, the earth was good to her. Two years after her daughter, Barbara Bernal, completed an off-the-grid beach house for her in Tunquen, Chile, an offshore 8.8-magnitude earthquake shook the South American coast. The temblor toppled buildings and triggered tsunamis, but Schneider’s stilted home stood strong, suffering only a few cracks in the drywall.

Dubbed the Casa Cuatro, the house floats atop a 180-foot cliff overlooking the Pacific Ocean, a 90-minute drive from Santiago and nearly as far from municipal utilities. In their place, Bernal and her partner Nick Foster (who work in Chile and Canada as Foster Bernal Architects) equipped the house with solar panels, a wind turbine, and a gravity-fed well and employed passive heating and cooling strategies. The only items tumbling any time soon are Schneider’s rummy tiles.

Thermal Mass Wall

Constructing the home with local timber and stone proved doubly beneficial: Not only were the designers able to take advantage of materials from the region, but the quarried surface serves as a thermal-mass wall, absorbing heat during the day and releasing it through the evening.

Passive Heating and Cooling

“You can go a long way to make a house sustainable in the early parts of the design process instead of throwing a lot of expensive technology at it later,” Foster says. He and Bernal opened the house to the eastern hillside as well as toward the westward ocean view to allow cross breezes to flow through the space—–and cool the house in as little as two minutes, Bernal says.

Bernal and Foster’s tips for designing a low-tech, highly efficient home:

Keep it simple, and build only what you need. By eliminating interior walls wherever possible, they reduced materials, waste, and costs.

Harness the sun. The duo installed solar panels, incorporated a thermal-mass wall, opened the eastern facade for warm morning rays, and built overhangs on the western side to prevent afternoon overheating.

Guide the wind. Bernal and Foster worked at least two windows or openings into every room to encourage cross ventilation and natural cooling.

Create a tight building envelope. Chile recently became one of the first South American countries to incorporate insulation into its building code. “People just accepted being cold a few months of the year rather than being comfortable and minimizing energy use and loss,” says Bernal, who shored up the Casa Cuatro to North American standards.

Xeriscaping

Bernal and Foster dream of a green roof but are currently content developing the xeriscaping (landscaping with a water-conserving agenda) on and around the house. “We’re trying to put gravel, patches of grass, and succulents up there, but right now it’s just the solar panels and green things, which are probably dead,” Bernal says. “We don’t want to install an irrigation system, so we’re working on what will stay alive in this climate.”

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Xeriscaping requires more than a green thumb: It also calls for careful site planning. San Francisco landscape architect Andrea Cochran offers these tips for getting your arid-climate garden to grow:

Plant natives. “Pay attention to what grows naturally and has the ability to survive on its own in your area,” Cochran says. If you can’t replicate your surroundings with foliage native to your region, choose plants indigenous to a similar climate.

Group plants based on similar water needs. Separate high-water-use plants from low-water-use plants with several feet of greenery that can survive wet and dry extremes, like some grasses.

Map the topography. Plant low-water-use plants at high spots in the yard to keep the roots from drowning where the water puddles.

Know your soil. If it’s claylike or doesn’t drain well, dig larger pits for the plants. “If they’re in a little teacup-size space, the water just sits at the bottom,” Cochran says.

Use mulch. Two to three inches on top will retain moisture and keep soil from drying out. “It can be stones or a bark mulch colored with charcoal so it’s sharp looking,” Cochran says. “It doesn’t have to be ugly.”

Irrigate at first. Some drought-tolerant plants need to be regularly
watered for several years before the roots get a good hold in the ground. Consider planting before the rainy season to optimize the plants’ chances of establishing themselves in their new environment.

Stilt Construction

Building a slab foundation makes sense where concrete trucks can cruise down the street but not in a remote location like La Boca, the sustainable community where the Casa Cuatro is sited. To reduce the financial and environmental costs of excavating, Bernal and Foster perched the majority of the house on piles. “The ridge floor is so fragile; we didn’t want to touch it and disturb the landscape,” Foster says. As a bonus, the air circulating underneath helps naturally cool the house.

Wind-Powered Well and Gravity-Fed Water Supply

Residents of La Boca have two choices when it comes to water: Dig a well or pay to have water delivered to a personal holding tank. After crews unsuccessfully dug one 150-foot-deep hole, they got lucky and hit a source on the second attempt. Solar panels and a 1,800-watt wind turbine power a pump that brings the water to a tank on the hill behind the house. The water then flows to the home as needed with gravity’s helping hand.

Solar Panels

Because the Casa Cuatro is a weekend home, Schneider needs only general lighting and a refrigerator to electrically power her through her two-day getaways of gardening, cooking, game playing, and swimming. Four 85-watt Kyocera panels supply enough energy to run the appliances and bulbs as well as the water pump.