Radiant Ceiling Heat

Old 03-29-05, 05:08 PM
Visiting Guest
Posts: n/a
Radiant Ceiling Heat

Hey guys, I have a question about Radiant Ceiling Heat. Our house that we live in was built by my great-grandfather in 1950 and has hot water radiant heat piped through the attic to radiators located just above the plaster ceiling, not embedded like many people's radiant heat systems. My father and I were curious about why the heat system designer decide to put the radiant heat system in the ceiling instead of in the floor, since heat naturally rises. Incidentally a secondary system is also placed under the concrete foundation to supplement the other system on cold days, but the circulator pump for this system is operated off of a switch, so that you can turn it on and off as needed, while the radiant ceiling system is a 3-zone system. Again we were just curious why they would put the primary system in the ceiling. If anyone has any ideas it would be appreciated. Thanks
Old 03-29-05, 05:29 PM
Visiting Guest
Posts: n/a
The big myth...

...contrary to the most popular myth of all...heat does not rise.

Hot air does.

Radiant on other hand travels in any direction as long as there is a temperature difference....otherwise we'd all have to stand on top of the sun to stay warm...

So in your case if the temperature of the plaster ceiling is lower than the temperature of the radiator then it will absorb energy from the hotter surface and rise in temperature becoming its own radiator. If the ceiling "sees" anything cooler than itself it will release its energy as it tries to reach a thermal equilibrium with its surroundings.

All clear?


Last edited by RBean; 03-29-05 at 08:59 PM. Reason: than to then
Old 03-29-05, 05:35 PM
Join Date: Feb 2005
Location: New England
Posts: 68
Upvotes: 0
Received 0 Upvotes on 0 Posts
Radiant Ceiling Heat


RADIANT HEAT behaves & is transmitted in a different way than other kinds of heating energy; most U.S. homes are heated by CONVECTIVE heat, such as scorched air from a furnace, or convective hot air from a baseboard system: the heating elements HEAT THE AIR, then the HEATED AIR HEATS THE PEOPLE IN THE ROOM; since air can't hold a lot of btu's of heat, the air quickly cools & must be heated over & over again, which is not as efficient as radiant.

RADIANT HEAT operates differently; it relies on a THERMAL MASS, such as the entire heated ceiling "slab" or a heated concrete floor "slab" or a large heated cast iron radiator "slab" of metal to send out RADIANT WAVES OF HEAT ENERGY; in the case of the ceiling, the ENTIRE CEILING becomes a gigantic radiator that ACCUMULATES all these tens of thousands of warm btu's of heat from the heating pipes & releases them into the living space.

This heat energy (like the sun's rays) has to hit a solid object before the object is heated; the object can be people in the room, the carpet, the floor, furniture, a table, etc.; it is not felt as intensely as standing next to a blazing fireplace, but it heats in exactly the same way.

Radiant ceiling panels were widely installed in the 1950's & 1960's when radiant heat was first introduced in the U.S., because this is the LARGEST THERMAL MASS object in most U.S. homes; in later decades, concrete slabs & "gypcrete" lite concrete became popular & the "thermal mass" of choice in newer homes, so radiant mostly shifted to floor installation in the U.S.; like a massive object such as a ceiling, you can pump a LOT OF BTU'S OF HEAT into a concrete slab over a period of hours, & then allow the warm slab to radiate its heat into the building's living quarters.

There's nothing wrong with ceiling radiant; it is very widely & successfully used in Europe, which has a much wider usage of radiant heat than the U.S. & is also widely used in commercial buildings in the U.S, Europe & elsewhere with success.

Last edited by Chimney Cricket; 03-29-05 at 06:00 PM.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: