Homes warm to Earth’s power

Anyone who ever tried to dig a hole in January knows how hard the cold earth can be. However, underneath that top layer of soil, the earth is a warmer, more constant temperature no matter what the calendar says.

Home builders are starting to take advantage of that by introducing geothermal heat pumps into homes new and old. The concept is simple and dates to the 1800s, but not until the 1940s did any buildings start delivering on its promise.

Traditional furnace and air-conditioning systems have to work harder than geothermal systems and expend more energy to keep homes comfortable, supporters of the technology say. In the summer, the sticky, hot air is brought to a cooler temperature via air-conditioning units, and the home furnace kicks in come winter to make the crisp air tolerable.

Geothermal heat pumps, however, use the Earth’s natural stasis temperature — an average of roughly 58 degrees — to heat and cool homes more efficiently. As any green builder will quickly point out, the Earth’s heat is a renewable resource.

These heat pumps work through a series of pipes built as a loop installed underneath a house. During winter, fluid carrying the Earth’s natural heat pumps through the pipes and into a home’s indoor geo-exchange device. That releases warmer air into the home, typically through duct fans placed throughout the house.

Come spring and summer, the process reverses itself. Heat is drawn from the home via the piping loop and absorbed by the ground. The process works like a refrigerator, which draws heat from its interior to keep perishables cool, according to the District-based Geothermal Heat Pump Consortium Inc.

Geothermal heat pumps run quietly and usually are installed in a basement or attic. They also are far more energy-efficient than existing temperature systems and produce lower utility bills as well.

The catches with the system are less than with such other renewable energy sources such as wind and solar power. The systems are more expensive to install than traditional heating and cooling units, but sources say the units pay for themselves within five to seven years.

Many contend that utility bills drop dramatically with these systems.

Glenn Chinery, a mechanical engineer with the Environmental Protection Agency’s Energy Star program, calls geothermal heat pumps a “good, mature technology.”

“If you’re in a mild climate like San Diego, it’s not worth it … but if you’re in a Nashville or Atlanta, it can really save a lot of money,” Mr. Chinery says.

Installers can introduce the heat pumps in one of two ways, either via vertical or horizontal drilling. The former is better in places where homes are tightly packed, such as in the District.

Mr. Chinery lives in a Silver Spring condominium in which the building uses geothermal heat pumps.

“The utility bills are extremely low,” Mr. Chinery says, adding that each drilled well where the piping tunnels under his building is a few inches in diameter.

Lisa McArthur, assistant director with the Oklahoma-based International Ground Source Heat Pump Association, says that though the energy concept remains the same for these heat pumps, technology has improved the way they work.

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