Heat can be transferred where it is needed by convection, for example, from heated air blown by a forced air furnace, or by conduction such as how an egg cooks in a pan on the hot element of an electric range. A third type of heat transfer is radiation or radiant heating.
Radiant heat occurs when a warm surface gives up its heat to a cooler surface. Although hydronic and electric baseboard systems produce radiant heat, they are not considered true radiant heaters as these systems produce only a small percent of radiant energy and primarily heat air.
A distinctive characteristic of radiant heating is that it does not involve heating a medium such as a gas, liquid or solid to transfer heat. The sun is a good example of radiant heat. It transfers heat energy via electromagnetic waves, invisible energy waves that travel at the speed of light, without depending on or warming the media (the vacuum of deep space or the atmosphere of earth) through which its rays travel. The radiant infrared energy of the sun goes directly into and warms the people or objects in the path of the energy waves.
Radiant heating systems encompass several similar but uniquely distinctive technologies. Electric in-floor, wall panel or ceiling panel heating systems flow electricity through cables or wires which in turn heat up and radiate energy through the floor or panel to the people and objects within the room or building.
Another form of radiant heating is infrared heating. Infrared heaters use the full spectrum of electromagnetic waves to transfer energy that becomes heat once it encounters a solid object. Electromagnetic waves can be short, medium or long wavelength. Shorter wave-lengths are associated with higher temperatures and greater intensity or penetrating power of radiation. Longer wave-lengths produce lower temperatures and intensities.
Radiant heat is especially useful in outdoor applications such as snow melting, providing warmth at entryways and on loading docks, and other spot heating needs because outdoor air movement would simply blow away air heated by other methods. It is also a practical option for primary space heating in buildings that are drafty or have high ceilings because the heat originates at floor level with the warmed floor, people and objects. Since no air movement is needed, floor drafts and cold spots are eliminated and dust, pollen and germs are less likely to circulate throughout the area. Radiant heat lends itself well to zoned heating. Each area can be controlled by a separate thermostat which can save energy and money when the heat is turned down or off in unused areas. And because the heat starts at floor level, the greatest amount of heat is delivered where it is needed rather than lost to the ceiling area.