Sometimes referred to as “Geothermal” , the ground source heat pump (GSHP) is becoming a common method of heating.
A ground source heat pump extracts heat from the ground usually via a closed loop of plastic pipe containing a Glycol antifreeze solution. This pipe is buried in the ground in vertical bore-holes or horizontal trenches. The advantage of the former is that you dont need to have a large garden, but a bore-hole can be expensive to drill.
With horizontal trenches a larger area is required but, if the space is available, they are cheaper to install than a bore-hole. The trenches take either straight pipe or coiled pipe, buried about 1.5 to 2m below the surface, and wet ground is preferable.
Ground-source heat pumps offer the best year-round efficiency and environmental advantages as the temperature of the soil remains relatively constant throughout the year.