In article , z wrote:
yeah, for either the floor or the ceiling to do much radiating, it
would have to be red hot. it's convecting.

False. For an object to radiate heat, it needs only to be warmer than its
surroundings.

friend of mine had a house built with "radiant heating" in the ceiling
decades ago, state of the art whenever it was built. they hated it.
didn't heat well, and it made the ceiling plasterboard or whatever it
was crack a lot. they said there was just that one brief period when
people were installing it, they stopped pretty quick when it turned
out to be a dud.

One incompetent installation invalidates the entire principle, huh?