Temperatures below freezing? Even then there is plenty of heat left!
The heat pump increases the heat from low temperatures (e.g. -5°C) to a higher, more comfortable temperature (e.g. 22 °C). This also works in freezing temperatures. The environment benefits as well, since no emissions are created locally. Now you cildren can breath easily.
Heat pumps work most economically when the difference between the heat source intake is as low as possible compared with the temperature of the heating circuit. Therefore, low temperature heating systems, such as radiant-floor or wall heatinf are the ideal partners for the heat pump.