Passive cooling: low running costs, but not entirely free

Passive cooling uses the cooler ground to remove heat from a building. In this mode, transferring cooling energy does not require the heat pump compressor to run, but circulation pumps and controls still operate. It is therefore more accurate to say cooling with low electricity consumption rather than free cooling. ^S15

This capability must be included in the specific system. For example, manufacturers offer models with integrated passive cooling or additional cooling modules. Not every installed ground source system is ready to cool without modifications. ^S14

Humidity is an important limit. Condensation can form if a surface is cooled too much, so temperature control, suitable insulation and coordinated controls are needed. Floor cooling is not the same as air conditioning with dehumidification. ^S16

Solar gains, window shading and room heat loads also affect the result. A promise that the system will cool in summer does not say what level of comfort can actually be achieved.

Before ordering: state from the outset that you want cooling. Ask for the necessary module, cooling emitters, condensation protection and the system's limits on the hottest days to be specified.