There are two different ways to cool a building. Passive cooling: This is where the brine medium or the groundwater absorbs the energy from the heating circuit via a heat exchanger and transfers it outside. This function is also called natural cooling, as it transfers the excess heat to the natural ambience. Apart from the control unit and circulation pump, the heat pump remains switched off. Active cooling: For this, the function of the heat pump is simply reversed. This method of cooling can be achieved with reverse operation. This means that the refrigerant circuit is reversed internally or reversal is achieved by an external changeover of the primary and secondary circuits. As with a fridge, the heat pump then actively generates a cooling capacity. This is called active cooling.