Unlike hot air, radiant heat will not go where it is not wanted. If you control the surface temperature of the emitting surface, then the temperature of the surrounding surfaces will regulate the amount of heat they will accept. This is a difficult principle to understand; I will try to explain it in a simpler way.

One thing that helps is to realize that living, warm blooded things do not need to be heated. They all have their own built in heating system. But they need to control how fast they lose heat. For instance, if your body is making 100 Btu's per hour and is losing 100 Btu's per hour, you would feel perfectly comfortable. One Btu is the amount of thermal energy required to raise one pound of water, one degree, in one hour. If your body is making more heat than you can get rid of, you will feel hot. If you are losing heat faster than you can produce it, you will feel cold.

So for the best comfort possible, you do no want to heat or cool the body, but to control how fast the body loses heat. Next is understanding how radiant heat works. Radiant heat actually describes how that thermal energy is transmitted from one solid object to another. Radiant heat is actually a low frequency radio wave that flows from the object with the highest temperature and is absorbed by any object that has a lower temperature. The remarkable thing about this process is that it does not heat the air between the two objects.

There are three methods of transferring thermal energy or heat: conduction, convection, and radiant. In all three ways the energy is being transferred from the object with the highest temperature to the colder one. There is no such thing as cold. Cold is simply the absence of heat. Heat or thermal energy is constantly seeking to move to any object colder than it is.

Conduction: is the direct transfer of thermal energy from one solid object to another by contact. Some examples are when you touch something that is cold or hot, or when you get into water. The denser, or heavier the object, the faster the heat will transfer. Also, the heat will transfer up or away from the gravitational pull at a much higher rate than down. Normally conduction is the most efficient or positive method of heat transfer. For instance nothing will cool or heat a person faster than emersion in a cold or hot liquid. We have all the seen the advertisements of someone pressing a cold can of soda against their forehead.

Convection: is the transfer of thermal energy from one object to another by heating air with one object and then transferring the air to another object to heat it. Once you understand the principles involved, it is easy to understand why this method is inefficient and uncomfortable. The first problem with this method is that moving air past the human body will carry heat away. (Chill factor) So you must raise the temperature of the air to offset this effect. This would be a benefit during cooling. The amount of heat that the body produces changes from one person to another, and also constantly changes with each individual. For instance, you will need more heat when you are hungry and when sleeping. For a person to feel perfectly comfortable, the air temperature around you would have to be constantly changing, and would have to surround each person with a different air temperature.

A large percentage of the heat in a forced air system is lost in the transferring or moving of the air. Also, forcing the air movement introduces differential pressures within the structure which causes infiltration problems.

Heating the air in a room still leaves all of the solid objects in the room cold. So your body is constantly losing heat by radiation to all of the objects around you, such as floors, windows, etc. And the air temperature must also be raised to offset these losses.

Radiant: is the transfer of thermal energy or heat by a low frequency radio wave. Radiant has some very different properties:

• It never transmits heat to something warmer than it is.
• The greater the difference in temperature, the more heat it transfers.
• It does not cause air movement.
• All the objects within the room become warm.
• It does not dry the air out.
• It will transmit in any direction that is needed.
• It is silent.
• It is very clean

The best thing about [radiant] is its ability to heat only those objects that need heat. For instance if the emitting surface is maintained at the proper temperature, it will always furnish you with the exact heat necessary to feel comfortable. As your body temperature drops, all the warm surfaces around you will increase their transmissions. If your body temperature rises, the transmissions decrease.

The one thing that anyone who has ever lived with a radiant floor heating system talks about is how even the comfort is, no matter where you move, you just feel very comfortable.