When it’s very hot or cold outside, your house has to work hard to make that air the perfect temperature for indoors. But if it were 55 degrees year-round, heating and cooling would be a lot easier. And that happens to be the temperature of the ground, from about six or eight feet down to as far as you can dig – a fact exploited by geothermal heating and cooling systems.
“It doesn’t matter how hot it is outside, or how cold it is outside,” said Ryk Lesser of Green Energy Design & General Store in Easton, Md.
Though not widely used, geothermal heat-pump systems are growing in popularity as people look for environmentally friendly ways to heat and cool their houses while saving money, contractors say.
They are considered one of the best options for those who want to make their homes as energy-efficient as possible. However, geothermal systems can cost twice as much to install as their conventional counterparts, and it can take years to recoup the extra money.
The basic setup of a geothermal heat-pump system (not to be confused with a system that pulls energy from hot springs underground) resembles a conventional heat-pump system.
Even when it’s very cold, there is still some heat in the air, and a conventional heat pump pulls that warmth into your house. With geothermal systems, pipes are buried and a liquid is run through them, and the heat from underground is brought inside. To cool the house, the process is reversed and heat is carried away.
Anjali Hansen’s family owned a solar construction company, so she wanted to make her 4,000-square-foot house in suburban Falls Church, Va., as energy-efficient as possible.
The house that used to sit on the site was knocked down, leaving just the foundation, chimney and brick walls. She has installed energy-efficient insulation and is putting in new windows that help keep inside air in and outside air out.
“Once I cool it, it will stay cool – but I still have to cool it,” Hansen said.
That led her to a geothermal heating and cooling system, which is being designed and installed by Michael Strasburg of On-Site Energy. Strasburg said such systems are growing in popularity, especially among people building houses of more than 7,500 square feet because it is easier for them to recoup the extra costs.
While the systems can be installed in existing houses, it is often easier with new construction, when the yard is torn up anyway.
There are a number of benefits to geothermal heating and cooling systems, according to contractors and homeowners. The main one is the financial and environmental savings that comes from using less energy to get a house to a comfortable temperature.
Other benefits are, literally, hidden: Pipes go in the yard, meaning they can’t get damaged by the elements, and there’s no noisy unit outside the house.
The systems do cost substantially more to buy and install, however. Jay Wilson of Geothermal Options of Fairfax, Va., said that a geothermal system for a 2,000-square-foot house could cost $10,000 more to install, or about twice as much as a conventional system, but bring $1,000 a year in savings.
If you’re staying in the house at least 10 years, you’ve recouped the cost of the system, he said.
Other contractors put the premium paid for a system at anywhere from 30 to 100 percent, and the amount it can reduce bills at 25 to 90 percent. Factors such as how the house is built, how big it is, and what kind of heating and cooling system is being replaced can affect the efficiency difference.
The federal government offers a tax credit of up to $2,000 for geothermal systems.
George James, who works with the Department of Energy’s green Building America program, said there are many less expensive steps that can help cut a home’s energy costs.
“A geothermal system is one option, but if you’re looking at the overall price point, the overall investment, there are things that can be done to reduce the energy use of a house” before putting one in, he said.
Those include effective insulation, using the proper windows for the climate, and a good mechanical ventilation system to keep the inside air in and outside air out.
“How much money a family can afford to put into it really determines the approach they use,” James said. “There isn’t just one magic bullet – if you do this, wow, your energy bill is going to be zero.”
Geothermal Options’ Wilson said making a house energy-efficient is key to getting the most out of a geothermal system.
“A geothermal system is a big investment, and I would never encourage someone to install one unless they captured some of the lower-hanging fruit in terms of energy efficiency,” he said.
A big cost of geothermal systems is having to put pipes into the ground. They can be buried, either parallel to the ground or perpendicular, in large wells.
Some yards are too small for horizontal pipes or have objects in the way, such as swimming pools or septic systems, said Green Energy Design’s Lesser.
Either pipe layout can be used with a closed- or open-loop system. An open-loop system pulls in groundwater to run through the pipes and then lets that water back out. A closed-loop system has a constant supply of liquid, generally water or a mix including water, that circulates.
While open-loop systems are slightly more efficient, there are concerns that they deplete the groundwater and then eject that water back out, possibly with contaminants, Wilson said.
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