Do you ever wonder why warming up by the fire on a chilly winter evening is so comforting? Or why we can always find our pets positioning themselves in the precise location of the sunbeam streaming in through our windows? These are examples of heat transferred by radiation. Heat from a source, in this case the fire or the sun, is transferred to the surrounding surfaces and objects by means of electromagnetic waves. By heating a surface directly, the user feels warmth and comfort immediately upon contact.
Radiant heating is one of the oldest and most efficient ways to heat a space. It’s history dates as far back as the Roman Empire, with the use of the hypocaust. In those times, the floor would be raised above the ground with tiled pillars and space would be left between the walls. Hot air and smoke from a wood furnace would be directed to these enclosed areas, heating the interior space but not polluting it. The warm air was then released outside through flues in the roof.
Today there are two main types of radiant heating systems, electric and hydronic.
In an electric system, thin cables or mats are built into the floor or laid in-between the subfloor and the finished floor. An electric system can be made even more efficient by including a thermal mass such as a thick concrete slab which can be heated at night when electricity is cheaper and slowly release the stored heat throughout the day. This system is best for smaller renovation projects or additions where it is impractical to extend the existing heating system into the new space.
Hydronic systems work by pumping hot water from a boiler or water heater through a network of tubes under the subfloor. This system is best for new construction or if the radiant heat system is the primary heat source for the building.
Any type of flooring can be used over a radiant heating system, although hard surfaces such as ceramic tile, wood or stone are preferable over carpet because the insulating qualities of the carpet may reduce heat flow. Radiant heating is often more efficient than other types of heating systems. Since the occupants are warmed directly by the floor and objects on the floor, it is possible to feel comfortable at a lower temperature. The system is easily zoned to avoid wasting energy on rooms that are not in use. Overall, it seems that radiant heating systems are a worthwhile and earth friendly investment. Or you could just put on a sweater.