The earth, water and air have the ability to absorb and store heat from the sun. For example, in the case of a ground source system this heat is extracted from the earth using a ground loop. In the case of an air source heat pump this harnesses solar energy found in the outdoor air. With this system there is no need for digging or drilling and installation is very quick and simple. It is ideal for urban sites where there is very little ground space. The ground loop is a continuous closed loop of special pipe buried around the building. A mixture of water and food grade anti-freeze is circulated through the buried pipes where it absorbs heat from the surrounding earth. The ground loop is connected to a heat pump inside a building that takes heat out of the circulating mixture and transfers it into a heating circuit and hot water tank.