Question

What are the next heating/cooling advancements beyond geothermal?

Asked by Tom M.
Rocky Hill, CT

I've heard of several options including heat pumps that are far more efficient.

Answer

Lucas Johnson

Answered by Lucas Johnson

Seattle, WA

Cascadia Consulting Group

September 25, 2012

Great question and yes indeed, heat pump technology has come a really long way in the last few years.

  • There are now solid options for both water heating and space conditioning.
  • Most importantly, heat pump technology is a critical component of reaching zero net energy performance in your building (along with LED lighting, induction stoves, good thermal envelope, and of course, solar PV).

The American Council for an Energy-Efficient Economy has some great material. Look under “Consumer Resources”. Also, I should note that to install any of this technology correctly, you will need to hire a BPI Accredited Contractor. Check www.bpi.org for local references.

Three types of heat pumps

To address your primary question, most residential geothermal systems utilize heat pump technology.

There are three basic types of heat pumps:

  1. Air-to-air heat pumps - heat exchange occurs with ambient air (cheapest option and work well in relatively mild climates)
  2. Air-to-water heat pumps - heat exchange occurs with water (relatively rare, yet cool examples exist on a community scale)
  3. Geothermal - heat exchange occurs with the earth (can be expensive to dig trenches, but needed for extreme climates)

Heat pump technology is pretty self descriptive in that it basically just moves heat from one place to another. Like your refrigerator, which provides a cool storage area, by moving heat into the coils below the fridge, heat pumps can provide air conditioning by removing heat from your home and “placing” it outside. Or, during winter, they provide heat by pulling heat from the ambient air and moving that into your home.

When it is extremely cold outside, this does not work very well, so you have the risk of relying upon a very expensive electric resistance back-up OR if you have a geothermal heat pump system, you will just need to heat the air from around 65 degrees. 

A geothermal heat pump

The most efficient heat pump system, which is arguably the most efficient space conditioning option, is a geothermal system.

  • However, the geothermal part is probably not needed in a relatively mild climate and an air-to-air heat pump would most likely be fine.
  • The air-to-air pump will be slightly less efficient to operate in comparison to geothermal, but the difference in upfront cost would be significant. 

Again, the “geothermal” part typically refers to the fact that the heat exchange (for heating or cooling) occurs with the earth, which has an effectively constant temperature at about 6 feet in depth. In extreme climates (where it gets very hot or cold outside) this is important because the space conditioning system is able supply the 65 degree air directly from the earth or heat the air from 65 degrees (rather than say trying to heat from -13 degrees in Minnesota).

Air seal and insulate first

Lastly, the most important thing to do before considering space conditioning, is air sealing and properly insulating your home.

Without doing this, you will just be wasting a large amount of energy while exposing yourself to health risks and lower comfort. Again, a BPI Accredited contractor in your area should be able to help you with further considerations as well as provide a bid for performing upgrades.

 

For more information:

Read "Is my home well-suited to geothermal?" a Q&A answered by Mick Dalrymple.

Also, check out Randy Potter's Q&A "I can't afford geothermal. Is an air-to-air heat pump my best option for heating?"

Tagged In: heating cooling

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