Several of the 80 homes he has sent kits to in 25 states nationwide live off the grid – with the help of natural sources, such as solar panels, micro-hydro turbines and windmills.

The Cosenos purchased two solar panels for their water heater and 10 other panels, which produce approximately 7 kilowatt hours a day in the summer and have added up to about 2,100 kilowatt hours in one year, from July 2006, when they moved in, to July, 2007.

Even Enertia homeowners who employ supplemental heat, rather than solar power, spend a small fraction of what they would on traditional home heating. On the cloudy East coast, heating cost is approximately a third of normal cost, Sykes said. In the West, where it’s sunnier, he expects little or no additional heat usage, or, as the Cosenos found, use of one cord of wood.

How it works
Sykes, a North Carolina University mechanical engineering graduate, began building stick homes, until a friend asked him to build a log home in 1973. During the process, he realized solid wood structures hold heat longer once warm and remain cool once cooled. Still, he knew there must be a better way than using passive solar energy; he strived to find a way to heat the north side of a house and keep the south side cooler with little more than the sun’s energy. He also began to study trees to find the most energy-efficient species.

To create the Enertia home, he turned to the Earth as a model. He reasoned that if the Earth, surrounded by -459 degree temperatures, could maintain a comfortable temperature for humans by the atmosphere that surrounds its huge mass — which stores and releases energy from the sun — so, too, could a house.

He employs three principles of nature: inertia, thermal currents and the energy capacity of wood.

“Inertia” refers to movement in the absence of external forces. In the Enertia home’s case, it refers to movement of warm and cool air. The home uses thermal inertia, or the night and day cycle, to raise the home’s temperature into a comfort zone. Massive wood walls made of four 2x8 laminated Southern yellow pines — among world’s densest trees due to their high resin content — store the sun’s energy by day and release it at night.

The key to the Enertia home is a small air channel between the outer solid wood wall (which adds extra insulation for a cold winter night) and an inner solid wall. A large sunroom, made almost all of windows on the south side, connects to an attic and, in turn, the basement through the air channel. The channel forms a convection loop.

Six feet below the earth’s surface, the temperature remains a constant 50 to 55 degrees. As the sun heats the sunroom, warm air rises from the southern end, into the attic, then travels toward the cooler air on the north side, distributing warm air to an otherwise cold area of a home. The Cosenos also let heat in by opening the windows in the main house, which adjoin the sunroom.

“It was almost like opening an oven because you would feel the heat coming in,” says Tom.

The solid walls hold the heat, releasing it throughout the night as radiant heat. In general, the house acts as a heat pump, using the natural energy of rising heat. A paddle fan at the peak jumpstarts the airflow loops. Snow becomes a bonus for the Enertia home, as sunrays bounce off the snow and into the sunspace.

During summer months, the air channel becomes a ventilation path. Hot air rises, pulling cool air from open windows in the basement and up through the air channel, or envelope. Hot air also escapes through attic vents in the east and west gables. The majority of sunrays, which are higher in the sky in the summer, reflect off of the R50-rated roof panels, manufactured from Styrofoam and paneling. The outer wall of the house also provides shade.

As easy as Lincoln Logs
While home building can’t be described as “easy,” the Enertia home is one of the more simple to assemble. Like log homes, it comes in a kit, which includes timbers for the four exterior walls and two interior walls (to create the air channel), flashings, gaskets, spline, fasteners, beams and rafters. Doors, windows, flooring and foam roof panels are priced separately.

Styles and sizes range from a simple 1,000-square foot living space (not including the basement) to an elaborately designed 6,800-square-foot-plus custom home, office or townhome.

A 1,018 square-foot (plus 672 sf. basement) package begins at $62,380, and the highest end, non-custom package begins at $262,360 for a 3,789 square-foot home (plus 2,704 sf. basement). Other options include garages, breezeways, extra logs for more headroom and so on. Shipping from North Carolina costs $1.75 to $2 per mile, and most homes fit on one or two trucks.

A sustainable home
Not only are solid wood structures more durable and fire retardant, but building out of Southern yellow pine helps sustainability. In the 1970s and 1980s, the government planted millions of Southern yellow pines to use for home building. However, builders turned to Canadian spruce and fir to cut costs. Now, Enertia uses yellow pines from a tree farm, at which employees plant two or more pines for each tree they remove.

One Enertia home prevents a half-million pounds of pollution from entering the atmosphere over the course of 30 years. In the United States, the energy homes use is about equal to the oil the nation imports. According to the Department of Energy, heating and cooling accounts for 55 percent of energy used in homes. In addition, an Enertia home sequester between 20 and 90 tons of carbon in its wooden structure, Sykes said.

He has been producing the homes since the late 1980s but believes that only now are they beginning to catch on, as “green building” becomes more and more popular. As he says, “The Enertia home is as green as it gets.”

Personal intrigue
On a July Saturday, Ron and Lynn Colson from Green Mountain, Colo., visit the Coseno’s house to “kick the tires,” so to speak. They want to buy a lot at the base of Sunlight Ski Area. They’ve been interested in solar energy since they moved to Green Mountain, but they couldn’t find an architect who had the know-how or could build a solar home cost effectively, so they settled for buying a house that receives solar heat with no way to circulate it.

They traveled to the Coseno’s home, thinking they might tell their architect to incorporate some of the Enertia technology, but by the time they spent an hour or so in the home, they were extremely impressed, saying, “Why go through the expense when you can buy a kit and customize it?” Lynn says before she saw it, she didn’t think she’d like the sunroom, because it might feel enclosed, but with the high ceilings rising up to the attic, it’s one of the brightest, coziest places in the house. And stunning views of the Spanish Peaks don’t hurt.

As for the Cosenos, they’re thrilled with their new home, and they want to share it with anyone who’s interested.

“It’s a smart house … it works as it’s designed … and the house smells good and has a warm feeling because it’s all natural,” Tom says. “It’s almost as if you want to slap people and say, ‘Wake up’ – to open up a little bit to active, passive solar heating.”