Biotic heat: have you come across it?

What the word covers

Biotic heat is a way of describing warmth that reaches the body without going through the air, as the sun does. The term is not a standard, it simply names a difference everyone has already felt, between standing in the sun on a cold day and standing in a room heated by convection.

Why the body does not react the same way

The skin exchanges continuously by radiation with the surfaces around it. When those surfaces are cold it loses heat even if the air is warm, and that is when a room at twenty degrees still feels uncomfortable. Warming the surfaces removes that loss.

What blown air does along the way

A convection system moves air, and therefore dust and whatever it carries. It dries the area it treats, it creates a movement you feel on the neck, and it stratifies the room between a cold floor and a warm ceiling. None of that is dangerous, all of it is uncomfortable.

Far infrared radiation

A radiant ceiling emits in the far infrared, at a surface temperature close to that of skin. There is therefore no glare, no burning sensation and no drying: the ambient air is barely involved in the exchange.

What that gives in a room

The felt temperature is higher than the air temperature, which allows the setpoint to be lowered. The floor stays warm, the walls stop being cold, and the sensation does not change according to where you stand.

The effect on air quality is developed on the page about the radiant ceiling and the air you breathe, and the general principle on the heated ceiling operating principle page.