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Geothermal heating and cooling: Can you benefit?

Marshall McCauley | Improvement Center Columnist | May 7, 2013

Even though geothermal heat pumps have been identified by the EPA and the Department of Energy as one of the most energy-efficient and environmentally sensitive of all the space conditioning systems, many homeowners are still in the dark about this type of residential heating and cooling option. Also known as ground-source heat and water-source heat, geothermal heating relies on the stable, year-round temperatures that are found beneath the surface of the earth to heat and cool your home.

A traditional furnace or boiler uses gas, oil, or electricity to create heat; however, a heat pump uses electricity to move heat from one place to another. For example, a heat pump can move heat from underneath the ground, or from ground water, into your home during the winter months, while it is also able to pull heat out of your house to cool it during the summertime. In essence, a geothermal heat pump provides an all-in-one system that replaces both a indoor furnace and an outdoor air-conditioning compressor.

Geothermal heat pump options for your home

The two most common types of geothermal heat pump systems that are used for residential heating and cooling are open-loop systems and closed-loop systems.

A closed-loop system moves heat from the earth into your home to heat it -- and from your home into the ground to cool it -- by circulating liquid through a large coil of plastic piping that is buried under the soil or submerged in a deep pond. As the liquid circulates through the system, the heat pump unit, which is installed inside the home, extracts and boosts the heat, distributing it throughout your home via traditional HVAC duct work.

http://upload.wikimedia.org/wikipedia/commons/1/15/Water_to_Water_Heat_Pump.jpg

An open loop system, sometimes called a "pump and dump" system, operates in much the same way, except that it relies on ground water to circulate the heat throughout the system. Ground water is pumped from a well into the heat pump unit, which extracts the heat and then dumps the water back into the ground by way of an injection well. Although the two systems use different methods of moving the heat from the ground to your house, both systems rely on a heat pump unit and similar interior mechanical equipment to distribute the heat.



     Water-to-water heat pump

Advantages of a heat pump system

  1. considered eco-friendly because there is no on-site combustion of fossil fuels
  2. long lasting and durable
  3. located either in the ground or in the home, so there are no noisy compressors or equipment outside your house
  4. heating and cooling options all in one unit
  5. can be retrofitted to use existing HVAC duct work
  6. lower operating costs over the life of the system
  7. until December 31, 2016, may qualify for federal tax credits up to 30 percent of the cost of system
  8. can generate domestic hot water from some heat pump systems
  9. uses traditional forced-air HVAC ducting, or some systems can be coupled with in-floor radiant heating

Disadvantages of a heat pump system

  1. high upfront costs, which can be 2-3 times the cost of a traditional forced air furnace
  2. closed loop systems require large amounts of land to bury the underground piping
  3. requires electricity, usually supplied by coal or natural gas-fired power plants, to power internal compressors and strip heaters
  4. requires constant moderate temperatures to operate most efficiently, unlike traditional furnaces that fluctuate from high to low heat settings throughout the day

Is a heat pump system right for your home?

There are many factors and variables to consider before you can determine if a heat pump system is right for your home. You should consult a professional HVAC installer with experience in heat pumps, who can calculate your home's heating and cooling needs and evaluate your property's suitability for geothermal heating. Although heat pump systems can be used in all climates throughout the country, your local building codes, ground temperatures, and ground-water availability all need be taken into account when designing and pricing a specific system for your home.

Warming up to geothermal heating takes time for many homeowners, as the long-term savings must be compared with the significant upfront costs of designing and installing the system. Yet, if you are looking for an all-in-one heating and cooling system that has serious green credentials, then a heat pump could be a contender.

About the Author

Marshall McCauley is a builder and freelance writer.