Radiant heat is quieter. Radiant heat is cleaner. Air temperature in the room is uniform, with little variance between ceiling and floor temperatures, so for the sickly, radiant heat is healthier. Radiant heat is more comfortable because of this uniformity. A warm surface emits heat to the space by infrared radiation.
Infrared radiation is electromagnetic radiation with a wavelength beyond visible light.
In 1800, William Herschel found that sunlight passed through a prism showed the greatest heating effect beyond the visible part of the spectrum, above the red color. Although heat from the sun is invisible to the human eye, it can be detected by instruments and, of course, you can feel it on your skin. All solid bodies above absolute zero radiate some energy in the infrared spectrum. As that energy is transferred from one object to another, the infrared light energy waves cause the object they strike to heat up. The temperature differential between the heated surface and the surrounding air and materials causes a radiant effect.