The air-to-air heat pump is best known as air conditioning. This type of heat pump works as follows: it extracts energy from the air and blows the heated air into the rooms to be heated. The investment cost is the lowest of all types of heat pumps since it is a very simple system. Moreover, it is easy to install in both renovation and new construction. Another advantage of an air-to-air heat pump is that it is a direct system with no intermediate steps. Furthermore, you can also purify the air in your home through the built-in filters and this type of heat pump can also be used for cooling. This system continues to work at an outside temperature of -15°C. Depending on that temperature, these heat pumps provide 2 to 4 times more energy than they need themselves. This type cannot be combined with underfloor heating and convectors.