The physical law tells us that heat normally flows from a warmer medium to a colder one. But can we move heat from
our cooler house and dump it to a higher outside environment in summer? And can we extract heat from a lower
temperature outside, to our warmer rooms in winter? The answer is yes if we use a heat pump. The heat pump does so
by essentially “pumping” heat up the temperature scale, transferring it from a cold material to a warmer one by adding
energy, usually in the form of electricity. The most common type of heat pump is the air-source heat pump, which
transfers heat between indoor and the outside air. Ground Source heat pumps (GSHPs) have been in use since late
1940s, they use the constant temperature of the earth as the exchange medium instead of the outside air temperature.