What Is Radiant Energy ?

How Radiant Energy Works

Hold your hand over a hot cup of coffee and feel the heat. The logical conclusion is that heat rises. Logical maybe, but incorrect! "Hot air" rises but "heat" can travel in any direction. That is why you can feel the heat of the cup when you place your hand to the side of it. Radiant energy transfer is caused by a warm surface giving up its heat to a cooler surface. Whenever there is a temperature difference between two surfaces, both surfaces will attempt to equalize. Radiant energy travels through space without heating the space itself. It only turns into heat when it contacts a cooler surface. Our human comfort relies just as much on radiant heat transfer as it does on air temperature, yet the majority of heating and air-conditioning professionals think only in terms of air temperature. As a result, Americans are missing out on a truly comfortable living environment in their own homes or places of business. By controlling both the air temperature and the radiant transfer, radiant panel systems deliver a comfort that is unsurpassed.

Temperature and Radiant Energy
Skin surface temperature, about 85°F, is generally warmer than the surrounding surfaces. This makes us a radiant panel. Stand by a large picture window in midwinter and you will feel the heat leaving your body. If the rate at which we radiate heat is correct, we feel comfortable. When the temperature difference between our body and the surrounding cool surfaces becomes too great, we have to put on a sweater to slow down the rate at which we are radiating. When the sun beats down on us through the window, we receive heat instead, and off comes the sweater. Our normal state is to lose heat at a constant and regulated rate. We are also designed to lose heat in other ways as well. Air coming in contact with our skin conducts away heat. Our skin is moist and moving air also causes evaporative cooling. A truly comfortable environment is one designed to draw heat away from our bodies at precisely the correct rate. A heated floor normally "feels" neutral. Its surface temperature is usually less than our body temperature, although the overall sensation is one of comfort. Only on very cold days when the floor is called on for maximum output will it actually "feel" warm. Heat coming from a wall radiator can be felt the closer you get to it because its surface is much warmer than your body. Radiant ceiling panels are also generally warmer than your body so you will feel some warmth on your head and shoulders. All these radiant systems are designed to match the heat loss of the human body in a way not possible by any other form of heating. Any of these radiant experiences are far more pleasant than being buffeted by the hot-then-cool breezes which are often associated with a forced-air furnace.

Cooling and Air Conditioning
Some radiant panel systems are capable of cooling by circulating cool water through the panel. All the principles of radiant transfer still apply. By providing a cool surface, all other surfaces, including our bodies, will give up heat to the panel. Just as in heating, this is extremely pleasant. Radiant panel cooling is most often done with ceiling panels although it can be accomplished using walls or floors. Floors become enjoyably cool, not cold. It is only when humidity is a factor that steps must be taken to avoid condensation on the panel. In this case, an auxiliary air-conditioning system is used to dry the air. Most often a separate air-conditioning system is installed. This could be a simplified central system or a split system with strategically placed units. The advantage is zoned cooling. Using zoned cooling and placing air registers in the ceiling (where they should be), will result in summer energy savings.