Radiant ceiling heating

When I try to illustrate this type of heating system, the very first and inevitable question that is asked of me is the following:

"But how can it work? The heat doesn't rise?"

Yes, it's true! Hot air rises to the top!
Who among us has never played with Chinese lanterns? Their ascent to the sky is guaranteed by the flame that heats the air inside them, as in the case of hot air balloons.

But then ... how can I expect to be heated by the ceiling above my head?

The explanation lies in the principle of operation of this system: irradiation.

Imagine yourself on a ski slope on a sunny, cloudless day. There are times when you can take off shirtless to sunbathe, experiencing a feeling of well-being. And this we manage to do despite the presence of snow around us and despite the very low air temperature around us, very close to 0 ° C! How come we don't feel cold?
The explanation is due to solar radiation! That is, our body "sees" a very large surface (even if very distant), that of the sun, with a very high temperature (we are talking about millions of degrees). The fact that the two surfaces, that of our body and that of the sun, "see" each other and are at different temperatures, guarantees the exchange of heat from the hottest to the coldest surface.
This heat exchange occurs "by radiation" and does not depend on the air! In fact, solar radiation passes through space, where there is no air, until it reaches the earth's surface.

As soon as the sun is covered by the clouds, the two surfaces (that of the sun and that of our body) are no longer "seen" and the phenomenon of irradiation ceases immediately. We feel the sensation of cold and we are forced to get dressed.

The radiant ceiling works the same way: the surface in question is not as large as the sun and it does not have the same temperature as the sun ... but it is much closer to us!

Our body "sees" a surface (that of the ceiling) at a higher temperature (about 29 °) and therefore undergoes a heat transmission by radiation!

It must be said that this heat exchange also takes place between the ceiling and the other surfaces of the room where we are, that is, the floor and walls. Therefore, with the system activated, over time all the surfaces heat up and consequently also the ambient air.

The proximity of the ceiling allows us to benefit from the heat exchange by radiation. For this reason the radiant ceiling system is valid in the case of rooms of standard height such as residential ones.

The same cannot be said for rooms of greater height, such as an industrial warehouse or a church, where it is necessary to resort to the radiant floor or wall system, or even other air conditioning solutions.

N.B. Image source: web