If you’re talking about Ditra Heat or Strataheat or similar electric floor warming systems, they’re not designed to heat up the room. They provide something like 12-15 watts per square foot. I used Strataheat in a bathroom, about 525 watts for 35 square feet heated in a 100 square foot room (it doesn’t go under the vanity, tub, behind the toilet, etc). Controlled by a thermostat installed in the mortar bed under the tiles. It can get about 15 degrees above ambient. House has forced air heat, can’t speak to a build using the floor heat like a radiator.