eothermal Technology is a method of heating and cooling a building. It takes advantage of the natural stable warmth stored in the earth. Normally the earth temperature is around 55 F (13 C) at depths of 10 ft. In climates warmer than 55 F (13 C), this can be used to cool a building, and in colder climates (those under 55 F or 13 C) it can be used for warmth. This is accomplished by one of a number of methods. A heat pump uses the extracted water or transfer fluid (such as water mixed with antifreeze) as a heat source in winter and a heat sink in summer. Some heat pumps provide heating and cooling via forced air distribution, and others through the heating and/or chilling of water for radiant type systems. Some systems are used to heat domestic hot water.