In the other thread about humidity levels during winter I mentioned that I've kept my solid wood acoustic guitars in a room with a certain humidity level, for several decades (I keep it at 40% or more during winter). What I did not say in that thread is that the the room has a heated floor - and the guitars are kept close to, or at the floor during storage, although in cases. I don't consider this a problem at all, because as Christy said, if your bare feet are comfortable on the floor your instrument should be too. The relative humidity level of the air is what's important.
I would be much more concerned about wall heaters and the like, they present a concentrated spot of heat which you will want to keep your instrument well away from. Radiant heat floors are generally not very warm, instead the heat is spread over a larger area.