So a radiator isn't a radiator at all...

Why you need to know about Radiant Heating

OK, it’s a fair cop!  For more than 150 years, the heating industry has been guilty of propagating  a basic misconception. That’s because a radiator isn’t really a radiator at all.

In truth, those heat-emitting devices that we all call radiators actually generate most of their heat not through radiation, but convection. When the radiator’s name was coined all those years ago, it should have been convector. It wasn’t, and the wrong name stuck – but the true definition of radiant heating (and cooling) is important because genuine radiant heating is now becoming increasingly popular, bringing great benefits for building owners and occupants alike.

By understanding the difference, we can also understand why radiant heating can be the best option.

Heating the air versus heating objects

Convection (also referred to as convective heat transfer) is the transfer of heat from one place to another by the movement of fluids or gases. Convection heat is carried from a warmer to a cooler body by an intermediate fluid such as air. In the context of space heating, convection means heating the air, which in turn will heat the people and things in contact with that air. Radiators generally distribute 80% of their output via convection.

Radiation (or, more precisely, thermal radiation) is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. Rather than heating the air in a space, radiant heating will warm only the solid objects in that space, for example the furniture and people in a room. For this same reason a person near a bonfire will feel radiant heat from the fire even if the surrounding air is very cold. Radiators distribute only about 20% of their output in this way.

Whether convection heating or radiant heating is best depends on the circumstances. As convection heating isn’t always the most effective option, Zehnder is also at the forefront of radiant heating. To achieve these two alternative kinds of heat generation, the difference is once again surprisingly simple - because radiator technology can be adapted so that the heat output is mostly radiant.

Radiant heating has a sunny disposition

If you took a radiator, removed the convectors from the back, insulated it and installed it in a ceiling, you would be converting it into a radiant panel. These changes would shift the output ratios from 20% radiant heat and 80% convection to 70% radiant heat and 30% convection.

This means a radiant panel, unlike a radiator, has a name that accurately describes its method of heating. Look up to the sun in the sky or look up to the radiant panels near the ceiling in a commercial or public building and you’ll see the same thing: a source of radiant heating, warming your body and all other solid objects in its ‘line of sight’.

One of the key advantages of radiant ceiling panels is that they can be positioned to ensure occupants benefit from the heat produced by directing the heat to the interior of the space and reducing or eliminating excessive temperatures on outer walls and ceilings. There are other advantages, in comfort levels, efficiency, and energy consumption – and not just for radiant heating, but cooling too.