Geothermal Heating and Cooling

Geothermal heat may sound like an advanced or unattainable goal, but it is quite real today. The science is sound: the Earth’s soil is much denser than our atmosphere, meaning it has much more thermal mass. Because of this, air temperatures from one season to another season vary dramatically. Even from noon to midnight, outside temperatures range from highs to lows. Surface soil will vary with the air temperature. However, if you dig a few feet into dirt, you will find that the temperature is much less prone to fluctuation.

In fact, the thermal properties of the earth are what allow us in cold winter climates to bury water pipes that lead to many homes without fear of frozen and burst water pipes. Our region mandates that water pipes must be buried between 5’ – 6’ deep (depending on your municipality). This depth is known to be below the frost line. Water in the soil above that 5’ mark, as well as water in shallow pipes such as irrigation lines, will freeze when the temperature gets low enough. That is why we blow out our sprinkler lines in the winter, or take other precautions. However, at a sufficient depth, the thermal mass of the earth acts as insulation from the freezing air. At 6’ deep, the earth is a relatively consistent temperature.

We have learned to take advantage of this thermal mass over the centuries. Ancient peoples were able to store ice in the desert heat by digging deep caverns into the earth. Not long ago, in our part of the country, root cellars were the choice to store food. These are making a comeback with modernized designs. Another use for the properties of the earth is geothermal heating and cooling. There are a few styles, some are closed loops and some actually take water from below the water table, extract heat, and return the water unused. Here’s how a closed loop system works:

After appropriate surveys and approvals are completed, a geothermal heating specialist will dig long trenches or deep wells into the earth. Hundreds of feet of pipe are laid throughout the trench or pit in one or more loops that connect into the house. The excavated dirt is replaced. Inside the house, the pipes are connected to a heat exchanger, which uses a conductive metal to transfer heat. Pipes are filled with a conductive liquid, and a pump circulates liquid in a continuous loop. During the winter months, when outside temperatures reach freezing, the soil is significantly warmer than the air. The liquid circulating through the pipes absorbs heat energy from the soil and moves into a heat exchanger, where heat energy is transferred into the house. The liquid in the pipes has now lost its heat energy and makes another loop through the pipes to absorb heat from the earth. Much like a gas furnace, fans and ducts assist in transferring heat throughout your home.

During summer months, the process works similarly. One major difference is that the house air temperature is higher than the soil temperature. So, the heat exchanger actually absorbs heat energy, transfers it into the liquid, and then the process works in reverse. Heat energy is now dumped into the earth (which is now colder than the outside air). The pipes have cooled down, the liquid travels inside, and is able to absorb heat energy from the house. The process is really quite smooth and simple. No major changes are necessary to transition from heating a home to cooling a home. Geothermal heating and cooling is able to maintain consistent room temperatures throughout the year with natural physics.

My favorite part is that, after several years, this system will pay for itself with the savings on your energy bill. Electric heating and cooling, heat pumps, natural gas, and all other sources of air conditioning require significant resources, which leads to significant expenses. With geothermal heating and cooling, your biggest expense is the circulation pump – which requires much less energy than other forms of heating and cooling. It also means less combustion byproducts are put out. The efficiency of the system is in the fact that we are not creating temperature changes, we are simply utilizing those differences that are already in our own backyard.

If you ever build a home or have to replace your HVAC system, consider the benefits of a geothermal system! Much like solar power, it’s a large up-front cost, but it will pay for itself in energy savings over the years.

Too Long, Didn't Read Version: Geothermal heating and cooling takes advantage of consistent soil temperatures below the surface of the earth to save resources when we heat and cool our homes. Instead of inefficient electric heaters, burning natural gas, or compressors with refrigerant gas – a closed loop system simply pumps water through buried pipes to transfer heat.

-Marshall Tramp, CPI, RMP

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Marshall Tramp, CPI, RMP
Author: Marshall Tramp, CPI, RMP
Top Notch Inspection Services llc
Serving Eastern Washington & Northern Idaho