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Case study: A net-zero-energy home

By on 03/16/2009

Here’s one mountaintop house that blends in with the stunning view instead of overpowering it: the net-zero-energy home owned by Yves Naar, designed by architect Stephens Smith Farrell and built by Doug Keefer’s company, SAGE Builders of WNC Inc.

Solar tilt: Yves Naar’s mountaintop perch uses a combination of approaches to achieve net-zero-energy use, including the system powered by these solar panels. photos by Jonathan Welch

After a pleasant drive south of Brevard and up a mountain road, the shrub-lined driveway brings you out of the trees and into a space of open sky. Far below, Conestee Lake shimmers in the sunlight. The near 360-degree view encompasses mountains, valleys and sky—and one 1,250-square-foot, flat-roofed house nestled at the edge. The upper level is all you see at first, as much of the home has been set into the mountainside. Approach the house, and you notice both the entryway patio and the roof are covered with hundreds of sedum plants. Both are features installed by a local company called—appropriately—Living Roof Inc. This isn’t your average house. Another clue is the lineup of four solar arrays that tilt sunward on a terraced spot to the left of the house.

“The customer wanted the greenest structure he could have,” says Keefer. From the site to the furniture, green choices were made at every stage, he explains. There was an existing home, driveway and utility service on the 42-acre site. Other than removing the older house, very little site-prep had to be done, Keefer continues. And Naar decided to build a guest-cottage-size house instead of the all-too-common mountaintop mansion. Smaller is better, because Naar wanted a home that produces as much energy as it consumes: a net-zero-energy house.

To accomplish that goal, the home is heated and cooled by a combination of geothermal and solar thermal systems. Underneath the lower level’s slate floor, for example, there’s hydronic radiant heat. The solar and geothermal systems preheat the water that runs through the pipes underneath the slab. The real beauty of the system is that Naar doesn’t store the electricity generated by the solar system; he sells it. Duke Energy buys Naar’s electricity at the wholesale rate of 3 cents per kilowatt, and N.C. Green Power pays an additional 18 cents per kilowatt as a clean-energy credit. The initial idea is to work toward breaking even, Keefer explains. The home has received the second-highest rating in the state for HealthyBuilt Homes, and the Energy Star System has given it the best HERS (Home Energy Rating System) in the state, he adds.

Keefer also emphasizes that green building means thinking about more than one aspect, such as the home’s heating, cooling and electrical systems. Early on, Naar made a commitment to green every component he could. The upstairs floors are reclaimed heart pine, finished with Earthpaint products. Some walls are painted with zero-VOC paints from the same local company; some have been done in a Venetian plaster; others feature such renewable or natural products as bamboo and jute. A bathroom countertop was made by Keefer from reclaimed walnut. The bathroom tiles are made of recycled marble. The kitchen backsplash is made of recycled plastic bottles with stones sandwiched between the layers. Timbers felled from the property support one level of the living roof that extends over the lower-level patio. Part of the exterior is stucco; other sections feature poplar bark siding (complete with the lichen that attaches to old trees).

Bathroom reclamation: This bathroom countertop is made out of a piece of walnut reclaimed by builder Doug Keefer.

Even the furniture has a green spin. Several rugs are made from leather recycled from a shoe or purse factory. Two funkadelic chairs are made out of multicolored, recycled cloth scraps. The dining room table was made with reclaimed wood, too.

Inside and out, the house is a lesson in texture.

It’s also a very grounded, earthy house. Perhaps that’s in part due to the geothermal system. The earth maintains a fairly constant temperature, in the range of 55 degrees or so, Keefer explains. With a little preheating from the solar system, it takes little energy to warm the floor, he continues.

As noted above, most of the lower level recedes into the hillside. It uses a poured-concrete foundation wall that’s insulated with foam board. The rest of the house is insulated with icyneme, Keefer points out. There are also some passive-solar elements in the home: Expansive windows on the lower-level living room warm the slate floor, which—because of its thermal mass—will hold and release that warmth well after sundown in the winter.

Keefer relays one of Naar’s core concepts for the house: “It’s a step toward sustainability. It’s a demonstration of what can be done.”

Margaret Williams is contributing editor at Mountain Xpress, and writes a weekly environmental news column for the newspaper called “Green Scene.” She can be reached at or at (828) 251-1333, ext. 152.