Underfloor heating is disastrous for a piano or any wooden instrument. The warm rising air of underfloor heating follows its way through your piano meanwhile dehydration the piano.
Glued joints will come loose and dry out. The wood will work and cracks and ruptures in the soundboard and pin block are the result. It is also possible that the mechanism will not function the way it should and the piano will detune rapidly.
A resonant soundboard, a piano which cannot be tuned any more, a very drastic and costly repair of the soundboard and the pin block. Most of the time repair costs are so high that the costs of repair are more than the value of your instrument.
Place a Pianocarpet under the instrument. Pianocarpet is a heatshield embedded in a carpet and designed to prevent the warm rising air of underfloor heating floating through your piano and protect the piano from dehydration.
With a Pianocarpet (heatshield) the warm rising air of underfloor heating has no direct access to your valuable instrument!