Feature Article | House Highlights | From the Photojournalist

The first LEED Platinum, net-zero-carbon house in Colorado—and maybe the nation—looks like it was built a century ago.

By Seth Masia

Bruce Oreck’s Next West house presides over one of the oldest neighborhoods in Boulder, Colo. The house fits right into the Mapleton Hill Historic District, as if it has been sitting on its hillside for a century.

In fact, the lot remained empty for generations while the neighborhood grew up around it. A narrow triangle on a steep hillside, it backed against an irrigation ditch, creating a true land-use challenge.

Oreck envisioned a house that would go beyond generating all its own energy on-site, producing enough carbon-free power over time to offset the embedded energy used in its construction.

“Let’s pretend it’s 1850,” he said. “You don’t have an energy grid. You need to design as if you don’t have energy, then put the energy in. You capture as much light and energy as you can, and plan to get light into interior spaces.”

For that purpose, the steep unbuildable site was perfect. The triangular lot, with its hypotenuse facing south, tilted sharply toward the sun and elevated the roof well above neighboring trees. The irrigation ditch required a massive retaining wall — Oreck calls it the Hoover Dam — but when it runs with water in the summer, it cools the backyard and patio perceptibly. The dam angles at one end to reflect light into the east-facing basement windows. Contractor Bob Hughes says that using pre-formed, interlocking concrete blocks kept the cost of the wall to about $50,000, less than 3 percent of the project budget.

During the last decades of the 19th century, the nicest houses in central Boulder were solid piles of masonry in classic Victorian style, built for mining, railroad and ranching magnates, lawyers, doctors and University of Colorado professors. From outside, Next West, faced with recycled brick and local quartzite, looks 100 years old. With its large windows and deeply shaded south-facing porch, the 3,800-square-foot house (353 square meters) seems a cousin to the adjacent 1890 Victorian. Like that house, Next West is built to last at least a century.

The Boulder Historical Society didn’t want to approve a house with solar panels, so architect Jim Logan agreed to hide them from passersby on the street. Edge around to the west and look up at the roof. It forms a double peak, with two east-west ridges and two south-facing surfaces. The back roof, hidden from the street, is faced with photovoltaic modules. Jet black SunPower modules were chosen to match visually with asphalt shingles (sunpowercorp.com). The back roof didn’t offer enough area to make up the 10 kilowatts Oreck wanted, so the front porch was sized to take an additional set of modules forming its entire roof.

Finally, two more PV modules were set flush into a “false” roof at the front. The sheath roof not only softens the visual impact of the modules but provides an extra layer of insulation for the real drainage plane. According to Sarah Marvez, project manager in Logan’s office, the crew built a full-scale mockup of the roof, to demonstrate the concept to the Historical Society, before finishing out the structure.

Oreck insisted that no special technologies be invented, designed or engineered for Next West. Every item in the house is readily available from a local warehouse.

The Sunpower PV array feeds a stack of 24 6-volt Absolyte batteries in the cellar, good for 896 amp-hours. The batteries can run the house for four stormy days if the grid goes down.

The house uses no natural gas. The kitchen range has a 92 percent-efficient induction cook top that heats only the contents of the pot and not the air around it (gas is about 45 percent efficient). Space heating and cooling are provided by an Econar Invision dual-compressor heat pump working off two 450-foot-deep geothermal wells under the driveway (econar.com). The heat pump, in effect a heater-chiller, circulates hot water through PEX tubing under the floors throughout the house. Each room has an independent Oventrop non-electric thermostat (oventrop-na.com). Even the one-car garage, equipped with a 230-volt vehicle-charging outlet, has a radiant floor.

Massive insulation and tight sealing make the house livable on nearly no energy input. The foundation walls are of insulated concrete forms, and the main floor is of structural insulated foam. Only the top floor is stick-built. All walls are R50 (interior walls, too, for silence and privacy); the roof is R95. All glazing is of triple-pane superinsulated construction, and the windows are large enough for plentiful solar gain. The view over the trees to the south is of Boulder’s magnificent Flatirons, the dramatic rock formation fronting the eastern escarpment of the Rockies.

Some features are pure 19th century. A large pantry off the kitchen, uninsulated on its north wall, functions as the equivalent of a root cellar. All woodwork, including the floors, is of sustainably harvested walnut.

Other features are pure 21st century. Every room is wired with Cat 5 LAN, coaxial and fiber optic cables to handle any kind of computer, communications or entertainment device. The cables even feed a tiny kids’ playroom under the eaves with its own yard-high door. All the countertops are American-made mineral quartz composite; the tiles are of recycled glass composite.

Lighting throughout uses LED lamps. They “burn” at 98˚F , (37˚C) — skin temperature — and thus are about 30 percent more efficient than fluorescent lamps, with the same color balance as the incandescent bulbs we’re used to.

Domestic water, cold and hot, travels in dedicated PEX tubing — that is, each faucet in each of the four and a half bathrooms has its own insulated line. Turning on a hot-water tap anywhere in the house moves water from the heater tank by the most direct, unbranched route. Hot water is nearly instant, without the use of booster tanks or pumps. Gray water is captured and purified to be cycled to the toilets. “Your pet could drink it,” Oreck notes.

Next West is the third solar project for Bruce and Cody Oreck. In 2001, they built an off-grid beach house in Baja California, Mexico, using a 15-kilowatt array to light four buildings, heat the hot tub and desalinate 1,800 gallons (6,800 liters) of seawater daily. It also drives an air conditioning unit in the inverter room.

In 2005, the Orecks retrofitted their century-old home in Boulder. The old house is a laboratory of sorts. In addition to efficiency upgrades, it now has both a solar water-heating system and a PV array, but Oreck says, “We’ve done a lot of experimenting there to find out what’s doable. It’s a work in progress.”

The reliance on off-the-shelf products meant that Next West went up quickly. Planning began early in 2007, and the certificate of occupancy came in October 2008.

“We set out to prove that sustainable can be luxurious,” Oreck says. He thinks they’ve done a pretty good job.

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Seth Masia is managing editor of SOLAR TODAY.

This article is published in the March 2009 issue of SOLAR TODAY.

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