Radiant floor heating has been around for centuries, and has recently been swinging back into favor. The Romans used a type of under-floor heating, called hypercaust heating, in their communal buildings from at least 25 BC. Pillars held the floor several feet off the ground creating a gap through which hot air and smoke, generated in a special ‘stoke-hole’ fire room, was piped. The smoke was vented through flues in the walls to small vents on the roof of the building.
A refined version of the Roman hypercaust system is available on the market today and is commonly referred to as air-heated radiant floors.
Air is no longer the favored medium for heating floors, giving way to electric and hydronic (liquid) systems. Electric cables or tubing for hot fluid are embedded in the floor and the heated floor warms the contents of the room through radiant heat transfer (i.e. is heats objects directly rather than heating the air between them).
Floor heating has several advantages over the more common forced air heating system. Because energy is not lost through ducts floor heating is usually more efficient than forced air systems, and there is no need to move air between rooms so it can be advantageous for allergy sufferers. Hydronic systems use very little electricity, so can be a good choice for those living in areas where electricity is very expensive. People rave about the winter-time comfort on in-floor heating. And because the distribution is embedded in the floor, you have tremendous flexibility with furniture placement–you don’t have to worry about blocking air vents, raditors, or baseboard heating.
Of course, nothing is without drawbacks and radiant floor heating is no exception. The thermal mass of floors can be large, which means that it takes a considerably longer to heat or cool them, making timed temperature changes more difficult. Depending on the efficiency of your home and the mass of your floor, you make not be able to turn down the system much at night. Also, using your floors to heat your house leads to more limited choices in flooring materials. Any flooring that insulates the room from the floor (e.g. carpets, luxurious rugs) decreases the response time of the system and the constant heat dries and cracks solid wood floors that weren’t properly acclimated. Perhaps the biggest downside, though, is the absense of ductwork makes air-conditioning with a traditional central air system more difficult.