What's the secret? What kind of technological breakthrough allows Hoffman and Valentine to stay cool in the summer and warm in the winter while still keeping their monthly utility bills so low? No breakthrough at all; in fact, their heater's been burning for billions of years. All it took was a willingness on their part to give solar energy a try and an architect familiar with passive solar heating techniques. The result, they say, is a comfortable, economical, environmentally friendly new home.
"Building a solar home just made sense," Hoffman says. "Living in the South, we wanted to accentuate the positive."
Unlike coal and other fossil fuels, the sun is the ultimate clean, renewable energy source. So if it also produces lower utility bills, why aren't more people opting for solar homes?
"People don't understand it, they don't think about it," says Kathleen Cleary, membership coordinator with the N.C. Solar Energy Association.
Hoffman agrees, saying, "People think you'll burn up if you use solar in the South," when in reality, "the solar isn't just to keep it warm in the winter, it's to keep it cool in the summer."
Originally, Hoffman explains, she and Valentine just wanted a new home where they and their pets would have some breathing room; specifically, they needed a place where they could keep their llamas and donkeys without violating any city or community ordinances. But when they found a south-facing lot in the woods of Chatham County, she says, "that's when we started thinking maybe we should design a solar house."
For passive solar homes, siting is everything. Alicia Ravetto, the architect who designed Hoffman and Valentine's three-bedroom house, says passive solar is a fairly simple technique that relies on the tracking of the sun. The winter sun rises south of east and sets south of west. So by facing the house to the south, with large south-side windows and 2-foot overhangs, passive solar homes let the sun do all the work. During the coldest months, the low winter sun shines in and warms the home; during warmer months, the home's southern orientation and overhangs help block the high summer sun's rays.
Landscaping the area around the house can be another important aspect of passive solar heating and cooling. Planting trees on the north, east and west sides of the house can help block the sunlight from smaller windows on those sides, while leaving the south side of the home free of trees helps ensure that the large, south-facing windows can collect as much winter sun as possible.
Along with its southern orientation, Hoffman and Valentine's home features a concrete first floor that absorbs heat from the sun, then continues radiating it to warm the house through the night. Ravetto points out that the floor also could have been tile or stone. In this case, though, the concrete was scored to give the appearance of slate tiles without the high cost.
For another source of heat during the winter, roughly 850 feet of pipe runs beneath the concrete floor, circulating hot water for radiant heating throughout the house. The pipes are divided into two zones so the home's non-south-facing rooms can use radiant heating when the south-facing rooms are being warmed by the sun.
Insulation for the house did cost a little more, Hoffman admits; the north, west and east walls used R-19 Fiberglas insulation, while the south wall used R-15 and the ceiling used R-30. Overall, though, she says she doubts the building costs for their $260,000 solar home were much different than they would've been for a traditional house.
"This is the house we would've built, but without Alicia we would've faced it the wrong direction," she says. By doing some planning at the front end, she says, the long-term savings of their solar home may be substantial.
"Utility bills are definitely less," she says. "And it's a lot more comfortable."
Proponents of solar energy point out that virtually every home we build is technically a solar home anyway--in other words, the sunlight will always be there, shining through windows and affecting the temperature inside the house. It's just a matter of whether we choose to plan ahead and use solar energy to our advantage or get beaten up by the sun's rays.
"The critical part is to work with a designer or builder who knows how to do it," says Ravetto, who has worked as an architect for the past 20 years in Argentina and the United States.
In addition to saving on monthly heating and cooling bills, solar-home owners can receive a substantial North Carolina tax credit: $3,500 for homes featuring passive solar energy techniques, and $1,400 for active solar elements such as photovoltaic panels, which convert light to electricity.
"The tax credit was a terrific incentive," Hoffman says.
Tom Vanderbeck, another solar-home owner in Chatham County, points out that since siting is so important to passive solar heating and cooling, people living in tightly packed city blocks may have trouble taking advantage of the sun's winter and summer rays.
Ravetto says there are things all homeowners can do, though, to help make sure the sunlight works for them instead of against them: opening up south-facing walls with more windows, adding insulation to the attic, using fans to improve air circulation throughout the house, or even installing photovoltaic panels for more active solar heating.
One of the greatest advantages of a solar home, Hoffman says, is that the large south-facing windows and natural solar heat almost give the feeling of being outdoors.
"We wanted the focal point of the house to be outside," she explains. "We wanted to bring the outside in." And so in searching for a more suitable home for their two donkeys and three llamas, Hoffman and Valentine believe they've managed to build themselves a more natural, comfortable home as well.