Builder digs deep to tout geothermal systems
Those who accept initial cost will save thousands in the end
By TRACY PULLEY
The Tennessean
March 2, 2008 

Local builder Bruce Hancock has always been interested in using energy-efficient technology in the homes he builds. When he started drawing up plans for his own home, he met with a heating and cooling engineer who mentioned a word he hadn't heard before: geothermal. When the engineer used the phrase "save over 50 percent in electricity costs," Hancock had heard enough. He was in.

Today the two-story, four-bedroom home in Brentwood's Windstone development is nearing completion, and it's already being heated by a geothermal system installed last spring. Hancock had to take a deep breath and focus on the long-term benefits of the system when he paid the $45,000 bill for installation, almost double the cost of installing a traditional condenser heating and cooling system. 

"It costs quite a bit more on the front end," Hancock admits. "But not only is it almost twice as efficient as a forced-air system, it lasts twice as long and has few components that can go wrong."

Transfer is efficient
Geothermal heating and cooling is not a new technology, but it's gaining in popularity as energy prices continue to rise and America shifts its focus to conservation. The system uses the earth's constant temperature (here in Nashville, about 59 degrees year-round) to provide a heat exchange process that is used to heat and cool a home.

For Hancock's 5,000-square-foot home, four eight-inch holes were drilled in the yard to a depth of 300 feet. "We have to go that deep," says engineer Bruce Wollaber of Comfort Engineered Systems, who designed Hancock's system, "because the earth is not a great conductor of heat. It takes a lot of surface area, about one 300-foot hole for every two tons of air conditioning."

High-density polyethylene pipes were placed in the holes and connected to the heat pump in the home's basement, with more pipes used to create a closed-loop system that circulates water, gaining heat from the earth in the winter and releasing heat to the earth in the summer. In colder climates, antifreeze is used instead of water.

The water heats or cools air that is blown through vents in the house like a traditional system, but because the earth maintains a much more constant temperature than the air (hovering at around that 59-degree mark instead of summer's 90-plus air temps or winter's dips to below 20) the system is able to work with greater efficiency. It eliminates the need for an above-ground condenser, something many homeowners consider an eyesore, and can be connected to the water heater, as Hancock chose to do.

"Going green is not inexpensive," Hancock admits. "I want to make this system really work, so I've also used a Tyvec house wrap, low-e double-glazed windows, Energy Star-rated appliances and formaldehyde-free blown-in insulation. . . . And then I'm going to take thermal imaging cameras and see where hot or cool air still comes out of the house, see where the gaps are. . . . I'm really trying to experiment with this."

Investment pays off
David Allard of Allard Ward Architects in Nashville believes in the geothermal experiment; he's been living with a geothermal system in his home for 10 years. "Basically it's the same technology that cools your refrigerator," he says.

He's noticed not only a 30-plus percent drop in his electric bill but also an unexpected benefit: "One nice thing is the air that's distributed is so much warmer," Allard says.

In terms of his business, Allard finds that industries and schools are more interested in geothermal technology than homeowners. "The initial expense is almost double, so usually we find commercial customers more receptive to the idea," Allard says.

One such customer is Currey Ingram Academy in Brentwood, which installed its geothermal system in 2002. Consulting engineer John Olert of Olert Engineering says the school found the extra initial investment already reaching the payoff point last year.

"We've designed a system for the high school, their next building project, and this time we're going 500 feet down," Olert says.

Olert is frustrated that not all clients see the long-term benefits of geothermal systems.

"I designed a system for my church; it was going to cost $119,000 more and they decided against it," he says. "In the year and a half since the new building opened, we've had problems with our boiler and skyrocketing energy costs. . . . They're already regretting the decision."

Geothermal technology is even touted by the folks selling electricity. At Nashville Electric Service, energy services manager Jim Purcell makes an effort to promote geothermal systems among the area's builders. "We try to make developers aware of the benefits," Purcell says. "It's by far the cheapest way to heat and cool your home. The larger the home, the better the savings."

Tennessee Valley Authority spokesman Gil Francis keeps an eye on the advance of geothermal projects in TVA's seven-state service area; he'd love to see geothermal technology become the standard rather than the exception.

"Cumberland Electric did a feasibility study when Sumner County was looking at a geothermal system for Portland High School. . . . They estimated a $2.5 million savings over 20 years," Francis says.

"We want the end user to save money. It benefits the TVA because we have to build fewer power plants. . . . If you think a heat pump is expensive, imagine what a power plant costs."