I was speaking to an engineer today about cooling our house should it need it. He was talking about fan coils when i mentioned cooling the slab with underfloor heating. His advised me not to due to condensation and the risk to the floor and concrete. He stated that it was due to the dew point/humidity in the house and the condensation around the pipes and on the floor. He stated it would form not just on the floor surface but under tiles and around the pipes Now i don't pretend to know