A Guide to the Basics of Geothermal Heating and Cooling Systems

New tax incentives and rebates make ground source heat pumps a no-brainer for the efficiency-minded.

| November/December 2010

  • In summer, heat from the building is discharged back into the colder ground.
  • In winter, pipes full of liquid pull heat up into the building via heat pumps.
  • In the middle of New York City, this 6,000-square-foot home and office is heated and cooled with a system of underground pipes burrowed 1,200 feet below the city streets.
    Photo By Paul Warchol

Though they don’t make any noise themselves, geothermal heating and cooling systems are booming these days as architects and homeowners recognize the wisdom in this decades-old, fossil fuel-independent technology. Once used mainly in commercial buildings, these efficient and durable systems are now installed in about 50,000 U.S. homes each year, according to the U.S. Department of Energy.

“Many people think geothermal is a new technology, which makes builders and homeowners reluctant to use it,” says Jim Bose, executive director of the International Ground Source Heat Pump Association (IGSHPA), a nonprofit that promotes ground source heat pump technology. “Actually, it’s an idea that’s more than 150 years old.”

Though geothermal systems can have a high upfront cost, savings in operating costs usually mean the systems pay for themselves in less than a decade. Most systems carry a 50-year warranty and operate at 50 to 70 percent higher efficiency than most other heating systems. As geothermal’s history of documented research and reliability grows, the technology will develop too, says Bose, who has worked in the geothermal industry since the 1970s. New tax incentives and rebates will drive residential use over the next five years, he predicts.

Geothermal basics 

Geothermal takes advantage of one of nature’s wonders—the earth’s nearly constant underground temperature of 45 to 75 degrees Fahrenheit—to provide year-round heating and cooling. Geothermal systems exchange heat with the earth using an underground network of pipes filled with water or refrigerant. In winter, the fluid pulls heat from the ground and transfers it to the house through a heat exchanger. An indoor fan system circulates air through the house. In summer, the system deposits heat from the house into the earth and brings cool air back in.

Nearly any home—old or new—can take advantage of versatile ground source heat pump (GHP) systems. Retrofits often use existing ductwork with minimal modifications, and the slinky loop system makes pipe installation possible even on small, tight lots.

4/10/2014 10:00:56 AM

Geothermal heating systems are a fantastic way of cutting down on costs while maximising efficiency of power within your home. I recently changed over to an http://www.underfloorheatingsystems.co.uk system which has worked wonders for me. It heats more efficiently then my previous central heating system, and keeps my feet nice and warm at the same time!

11/6/2013 9:05:32 AM

We built a new home in 1997 in Mississippi. Before building, we attended a multi-week workshop/course put on by the local utility company. We learned so much about insulation, energy efficiency, siting, etc. This helped us see the wisdom of injecting a bit more in construction costs up-front that would yield comfort & savings over the years of living there, especially since the house would be built on family land and we expected to live there a long time. We put in a Water Furnace Geothermal system with vertical loops. The installer first sat down with us to discuss our cubic air space, insulation R levels, types of windows, doors, orientation on the lot, etc. to determine the correct size system. Other contractors we knew just asked the square footage and said, "Oh you need about a ____ ton unit." We could not have been happier with our Geothermal unit. It was quiet, installed in an interior closet, thus was out of the weather & not steadily losing its SEER value, was extremely comfortable, not fluctuating hot & cold, hot & cold, like so many systems do. It was set up to heat our 80 gallon water heater for free with the waste heat from the air-conditioning, which of course in Mississippi is the much longer time of year. We NEVER ran out of hot water! Our house was totally electric, except for gas logs, which were more for emergency back-up than regular use, & our highest electric bill was $130 during an especially hot summer month. The one-story house was close to 2800 s.f. with 9 & 10' ceilings, lots of large windows, & built over a 42" crawl-space. Life has a way of changing our plans & I sold the house in 2008. All of the energy-efficient features were a real selling point too. If I ever build or extensively remodel a home again, I will choose Geothermal. I cannot highly recommend it enough! As an aside, I also had a central vacuum system installed during construction...another FANTASTIC decision!

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