Geothermal heat pumps use ground temperatures rather than burned fuel to heat and cool your home. Because ground temperatures throughout the country are pretty stable, geothermal heat pumps can be effectively used almost anywhere. That said, there are specific geological, hydrological and spatial characteristics of your particular yard that will influence how well a geothermal heat pump will help your installer determine the best type of ground loop (horizontal or vertical) for your site.
The composition and properties of your rocks and soil can affect heat transfer rates and need to be considered when designing a geothermal heating system. Soil with good heat transfer properties requires less piping than soil with poor heat transfer. The amount of soil available in your yard is another important factor – soil that is too rocky or shallow to trench may require a vertical loop system.
The availability of ground or surface water also plays a part in determining which type of ground loop system you need. Open loop systems require surface water, and factors such as depth, volume and water quality all play a part in determining whether or not you can use an open-loop system. There are also applications where groundwater can be used for open-loop systems, provided the water is of sufficient quality.
Before you purchase an open-loop geothermal system, make sure your installer has fully investigated your site’s hydrology so you can avoid things like aquifer depletion and groundwater contamination.
Probably the most important factor in determining the type of geothermal loop you’ll need in your yard is the amount of land you have. Horizontal loops require about 400 – 600 ft of piping per ton, laid in trenches dug five to six ft in the ground. Vertical ground loops can be installed in smaller yards in wells dug 150 – 300 ft into the ground. In general, horizontal ground loops are used in new construction and vertical are used in existing homes and buildings.