During non-drought years, rapid snowmelt off the mountains of northern Arizona can turn otherwise docile creeks in the central part of the state into raging rivers. Sudden rainstorms can transform dry canyons and arroyos into roiling pools. During the monsoon season, hard rainfall nourishes the desert, restores the water table, and produces flash floods.

When Cory and Barbara Krueger moved from Philadelphia to Cornville, Arizona, they knew they'd chosen to "live in a place where water is an issue," says Cory Krueger. And, not only because most of the year water is in short supply. This fact meant that they needed to conserve water resources. But, they might experience an overabundance during wet years as the property built on is next to Oak Creek, which joins with Spring Creek nearby.

Their property isn't merely in the floodplain, explains Reynold (Rennie) Radoccia, LEED-AP, architect, and principal of Architecture Works Green in Clarkdale, Arizona; the property is a floodway. So, even though the Krueger's wanted an all-electric, solar-powered sustainable home, addressing the floodway designation "was the most critical aspect of the project," Radoccia says.

Sustainability in a Floodway  

Because the home is elevated nine feet from the ground, masonry construction was out. Instead, the team used 2x4 wood-frame construction, installing 1.5 inches of urethane or spray-foam insulation on the outside with fiber cement board siding as cladding. "That gave us about R-24 in the walls," the architect says, "while allowing us to economize on the wood."

The roof includes wood trusses with 12 inches of spray foam insulation at the roof level to prevent high temperatures from heating the attic where the ductwork is located. "That way, temperatures in the attic are easier on the HVAC system," Radoccia explains. The team selected a three-ply roof system with 50-year shingle roofing. "We all went round and round on that roofing," he adds. "It was a difficult decision."

The 7.8 kW solar array on the roof powers the all-electric home, including the solar hot-water system. As for passive solar to warm the house, "the site itself wasn't ideal, but we overcame direct solar gain in the windows by including overhangs," Radoccia says. "The large deck on the northwest side of the house, which overlooks Oak Creek, has 10-foot overhangs that keep the western sun from penetrating the living spaces."

The elevated main level of the home has 12 inches of spray foam insulation between the joists, then an additional inch of rigid foam at the bottom of the joists. "It's completely sealed. There's no air circulation in there, so the floor temperature stays stable," he says. Windsor low-E, argon-filled, double-pane windows with wood frames and aluminum exterior cladding add to the home's airtightness and comfort.

An HRV (heat recovery ventilator) air-exchange system exhausts stale air and brings fresh HEPA-filtered air every 30 minutes. The high SEER electric heat pump HVAC system with programmable thermostats is electric. "Natural gas isn't available in the neighborhood," says Radoccia. "We had the option of using propane with a gas furnace, but because we wanted to have a solar grid-tied system, we decided the HVAC should be all-electric as the savings in electrical costs would offset the cost with the photovoltaic solar array."

A Forever Home 

Because the home is so well insulated, Krueger says, the temperature remains steady inside—despite winter dips into the 20s and summer's triple-digit temperatures. "It's a smart house," he adds. "We can connect the heating and cooling systems with the internet and program temperatures for our presence and absence, but in a well-insulated house, that doesn't matter so much."