To understand how radiant ceiling heating and cooling work, first we need to get the #1 myth out of the way before we discuss radiant ceiling in greater detail.
MYTH: “Heat goes up”
FACT: “Heat does goes down”. Just stay in the sun and feel it.
This principle should read like this: “hot air goes up and cold air goes down” unfortunately the bad habit of generalizing has made it known in the wrong way.
A radiant panel not only uses the air as a method of heat transfer but, as the name implies, uses mainly thermal radiation.
It is based on electromagnetic waves, the same physical principle that allows many other technologies to work, for example lightings, televisions, mobile phones. Don’t worry, even if X-rays are also electromagnetic waves, here we’re talking about waves characterized by different frequencies: the most physiological and natural electromagnetic waves, the ones radiated by the human body. To be more precise we are talking about infrared rays at low frequency that are emitted from surfaces at temperatures typical of biological organisms.
In common with all the other electromagnetic waves, they all travel at the speed of light.
A radiant ceiling heated only a few degrees more than the other surrounding surfaces, immediately emits infrared heat (thermal radiation) in all directions. These radiations directly warm any object or surface in the surrounding area, no matter if they are up or down.
In heating the thermal emission of the radiant ceiling it is almost exclusively of the radiation type since the air that is in contact with the ceiling, even though heated for a few inches, is trapped without a way of rising.
In cooling the radiant ceiling panels are cooled down, and rather than emit infrared radiation, they absorb the thermal output of surrounding objects, bodies and surfaces that become “radiators”. Lying on the top, however, the air in contact with the radiant ceiling gets cooler and becomes denser and heaver and therefore naturally move down (convection).
Typically radiant ceilings in cooling absorb heat for 60-70% by radiation and the remaining (30-40%) by natural convection. The combination of these two effects significantly increase the performance of a radiant ceiling compare to radiant floor.
And our body? With its surface temperature of about 86-96F is almost always warmer than the surrounding surfaces. In the winter it will emit less, holding for itself the metabolic heat and giving a feeling of warmth. In summer it will emit more giving that feeling of freshness (in this mechanism plays an obviously important role the clothing).
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