The Basics Of Geothermal Heat Pumps & The Geotechnical Properties Of Soil

According to, nearly half of the energy used in an average home in America is attributed to heating and cooling costs. Due to this, many homeowners are considering heating and cooling systems that are energy efficient. One such system is a geothermal heat pump, which is a bit different from an air heat pump. If you are building a new home or considering upgrading your heating and cooling system, here are a few important things to understand about the geotechnical properties of soil and how geothermal heat pumps work.

Geotechnical Properties of Soil

Soil holds solar heat. A geothermal heat pump uses the geotechnical properties of soil to transfer heat to or from your home. Soil is heated by the sun and maintains a more stable temperature, which means soil generally remains warmer throughout the colder months than air. This makes a geothermal heat pump more energy efficient than an air heat pump.

On days when the air temperatures lower drastically and the wind howls fiercely, air heat pumps have a hard time gathering heat. However, geothermal units that pull heat from the soil underground are able to keep up with the thermostat's demands to keep the house warm. While frost lines do tend to deepen during the winter, soil temperature rarely reaches temperatures low enough to affect a geothermal heating system. For example, less energy is used to produce heat by a heat pump when the starting temperature is 35 degrees Fahrenheit as opposed to a starting air temperature of 15 degrees Fahrenheit.

Soil has various insulation properties. The type of soil can make an impact on the energy efficiency of the geothermal heat pump system. Dense soils, such as rock or clay, have very few air pockets and tend to hold heat better. Sandy or dry soil typically has too many air pockets, even though the pockets of air are small.

These air pockets act as an insulating barrier and hinders the transfer of heat from the soil to the coils that are installed underground to collect the heat. The denser the soil is, such as soil that is moist with ground water, the easier it is for heat to transfer.

How Geothermal Heat Pumps Work

Now that you have a basic understanding of why soil is a good fuel source for a heat pump, you are probably wondering how a geothermal heat pump works. This system uses a series of underground coils called a loop field, a compressor, an air handler and duct work.

When warm air is needed during the cooler months, refrigerant is sent through the loop field to collect heat from the soil then circulated to the compressor. The compressor compresses the refrigerant which causes the liquid to increase in temperature. The heated refrigerant then goes to an air handler via tubes.

The air handler forces air over the tubes and into the duct work. As the air flows over the tubes, the refrigerant inside the tubes lowers in temperature. When the refrigerant no longer holds any heat, it is recirculated back through the loop field again to collect more heat from the soil.

The system works in reverse during the summer months. Instead of pulling heat from the soil, the system pulls heat from the interior of the home. The air handler forces air over the cooled tubes and into the duct work to reduce the temperature inside the home.

Geothermal heat pumps do use energy but not to generate heat. The only energy used is to circulate and compress the refrigerant, and to force air over the tubes and into the home through the duct work. If you are concerned about using electricity, consider installing solar panels to provide power to the heat pump system.