Radiant in ceiling

Kal Row

you need to micro engineer anyway…

had a guy with an un-usable bathroom cause all the tubes for the floor ran from a manifold there – and the bath was 110F – he has no recourse but to chop it up and insulate on top of the bundle – for this ,“ceiling”, is much more flexible than slab – as you can simply “hang’em’high” until you get to your load destination

you could put tube in the floor, ceiling, walls, counters, everywhere and then balance until you feel nothing - i have offered this - so far no takers.

Unknown

The meat of the point is that comfort means more than noticeably warm floors.

If they do not know why they are comfortable, that doesn't make them less comfortable.

Like I said though.. if you're doing a slab system, go for it. It's not hard to pipe traffic areas only in concrete. But for every other method on the planet, it's a bit harder to accomodate 'traffic area only' piping. *and it's not necessary in the first place*. For all of those systems, you can cut the cost of the system in half, keep comfort comparable, and forget all the floor covering conversations by going into the ceiling.

Are you only doing slab systems? If so, that must take a lot more conversation than the comfort vs warm toes conversation normally does.

Weezbo

as a thought....

tangentical as it were to the conversation....making a header up in the floor joist beneath the gypcrete and only running the returns through the bathroom floor with a riser into an inspection panel, .... keep the Tails short coming into the wall ...would then have the bath room seeing the cooler return water temps and not all the supply side of the heating system...

with 110 it must be slab on grade...

jp_2

gravity

I'm not sure of the exact definition, but i think things like FA are also considered convection, as in BB, you don't say its conduction, then convection.

ans remember of course, as still as the air seems to be, its moving like crazy.

i think theres a lot more convection going on with a radiant floors than most people think, our thinking is more along the lines of BB where its real strong, so a floor seems real weak or non existant.

GMcD

Baseboards

Why do you think finned tube baseboard has all those fins? The fins Conduct heat from the fluid in the pipe, through the pipe wall to a huge surface area made up of all the fins. Those fins then Conduct heat to the boundary layer of air next to them. That warmed boundary layer of air then rises, creating an air Convection pattern. Cool air at the air space below the fins gets "sucked" up into the fins to replace the bouyant air rising off the fins. The motive force that creates that room air Convection pattern is the heated element and fins in the baseboard. There needs to be a good delta T in the first place to start, and maintain a continuous Convection airflow pattern. The now moving Convective air pattern continually removes heat via Convection away from the fins, once the air movement is started by the initial heating of that boundary layer of air that was initially heated by Conduction from the fin surface to the air.

Google "heat transfer basics" and read all about it.

Unknown

If you want to be really anal, you could make a case that there is no such thing as convection. You only conduct or radiate.. and the object you conducted or radiated to could move afterwards, such as some air molecules rising, letting you conduct or radiate again more easily to the replacement, cooler masses... but ultimately you are only conducting or radiating from one molecule to another. Convection is really no different than heating up a brick and then throwing the brick around

far out man! hehehehe....

GMcD

CCR

And that doesn't mean a certain rock band- conduction, convection, and radiation, the holy trinity of heat transfer.

I like the flying hot brick thing, that's what's known as "forced convection", like how some basic science has to be forced to counter "opinion", it may come down to flying bricks....

jp_2

like i said

you could be right, don;t remember the exact definition, google isn't always right either though

jp_2

good debate Geofff

now we get to a question I have no asnwer for:

what we are really talking about is the collision energy transfer from the wall/floor/ceiling and the colliding molecule.

we(phyiscs lecture) never talked about 'how' this energy transfered(collision energy). I do question conduction since, like I said early, this happens within fraction of a nanosecond i assume.

i'll ask a physist i know.

GMcD

Conduction from a warm surface to air (or any gas)

Ask your physicist all you want, he'll tell you the same things. Conduction from a hot surface to a gas like air occurs on a molecule by molecule basis. We all know that air at a certain temperature has some amount of energetic movement (brownian motion). A warmer air molecule has more energy than a cooler one, so when the warmer one bumps into a cooler one, heat transfer occurs (via conduction and radiation) till both molecules are at an equilibrium temperature.

As you know, since air molecules are spread pretty far apart, relatively speaking, it takes a while for enough air molecules to be warmed enouh to start to rise as a group above their cooler counterparts. Think herd mentality. So once you have enough warm air molecules wanting to rise, since they are lighter in that group than the cooler air nearby, they start a Convective air motion, and more cooler molecules must get "sucked in" behind them to make up for the vacuum the rising warmed air molecules left.

It's NOT "collision energy" specifically, it's heat transfer using all three modes - conduction, convection, and radiation. A warm surface will also be heating up individual molecules of gas (air) by direct radiation, by direct conduction- as each air molecule comes into contact with the warm surface, and by convection- as the moving air particles move past the warm surface colliding with that warm surface at a faster rate.

singh

perimeter heat

Let's not forget about just adding radiant ceiling to the outside walls, if load can be satisfied with a 4' band along the perimeter. This can also reduce that "burning sensation" ( plus a course of antibotics : ) )

John , you still here???? Great topic !!



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Weezbo

The last time i went camping..and i will have to rely on distant

memories here...:) i stacked large stones around the fire and selected a few particularily hefty ones to make a bit of a wall around one side of the fire...here is my reasoning i heat the heck out of the gert rock or two.. then i rearrange the stones a bit and remove the larger two for a bench and a place to rest the coffee pot..it is all radiant heat convection is fast moving particles..rocks dont move real fast so the heat they have is captivated as it were :)i have to think that the molecules of heated gases are moving quickest Above the fire...try this reach into a fire and draw out an ember.."when you clothe yourself in the truth you will not be burned"...maybe that is one of my favorite quotes...

Weezbo

Because the heat loss is greater at the perimiter top plates

one has an interesting thing happening with radiant ceilings....think about it ...heat goes to cold...and as insulative as plant cell structure may be it is a long way off by Far from an insulated ceiling wall eh?

just practising my Canadian ...:)

what i am saying is that Geoff is not leaving out any of the more salient points regarding radiant ceilings as near as i can determine *~/:)

ScottMP

Whats Left

is whats right.

After you've done everything else wrong !

There is no gravity, its just that the earth sucks.

Good thread, allthought I think it has degraded into a thermodynamics class.

So can we say that cieling radiant works ??

Scott

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[Deleted User]

Radiant ceilings work fantastically.

As everyone else who lives with them has said (Annectdotal?) they work really well. Are they as comfortable as a radiant floor? Given overall human comfort, I'd have to say yes. Can they cause the hot head syndrome? Absolutely, if allowed to run wild. But then again, the biggest complaint we get from people with radiant floors (installed by others) is discomfort due to over temp conditions. You find out what MEAN radiant temperature is REALLY all about in some cases.

In my case and any house I've ever been in, the floor temp is actually higher in rooms with RCH than in rooms without. In older parts of Denver with RCH, the consumer thinks they have RFH until I come in with my IR thermometer and prove them wrong.

As for the cold knee hole syndrome, that can be covered with one of those electric floor mats. A minor trade off for the overall comfort provided by RCH systems.

I've said it before, and I'll say it again, radiant ceilings and radiant walls are one of the most overlooked, easiest retrofit potentials in the retrofit market today.

And as Rob said, the consumer is no less satisfied to the point of disappointment because they went with RCH instead of RFH. In general, they are VERY comfortable.

If Rich Trethewey had done RCH instead of RFH on This Old House, we'd all be looking upwards instead of downwards :-)

So, in short, yes it works and works quite well.

ME

jp_2

better go back to schoool

lots of errors here geoff.

for one thing you are mixing theories of macro and micro systems.

when talking about molecules, you really do not talk about "heat transfer" or temperature of a molecule.

""""A warmer air molecule has more energy than a cooler one, so when the warmer one bumps into a cooler one, heat transfer occurs (via conduction and radiation) till both molecules are at an equilibrium temperature."""

thats not how it works. "til both are at same temp?" how on earhth would that happen? do they hold hands until they are the same?

"""It's NOT "collision energy" specifically, it's heat transfer using all three modes - conduction, convection, and radiation. """"

go back and read about molecular forces, you've find gravity to be a very weak force, therefore talking convection at the micro level make no sense at all.

and sorry it is "collision energy", since molecular speeds are what they are conduction and radiant transfer make no ssense either. you can quickly touch a very hot surface with your hand without burning, how is a molecule to pick up energy in such a nano time frame?

GMcD

J-P

Don't get personal J-P- I've been to School, and you were the one in many of your posts above being "confused" and not knowing what the answers are. I've tried to condense textbook thick heat transfer physics into short snippets for the broad readership, and you now seem to have become the expert, in spite of your comments to the contrary in your other posts.

Your turn- enlighten us as to the mechanisms of heat transfer from a warm surface to the surrounding air, both from a floor surface as well as a flat ceiling surface, in a closed room with no other means of air being moved into/out of the room.

Glenn Sossin_2

Very interesting but ..


The head is the warmest part of the body, the feet are the coldest part of the body. It would seem to me, you would be most comfortable with the feet being in contact with a warm floor - not your head.

I did a radiant ceiling in my basement during a major house renovation. Personally, I don't think it compares to a nice evenly heated floor.

Gordy

In Basement

Radiant ceiling may have a problem keeping the floor warm, if the basement slab is not insulated. I would deffinetly go with RFH in a basement first,and RCH second as a retrofit if height is an issue in a basement.

I have rooms in my house with both RFH, and RCH talk about a radiantmakin sandwich.

Personally I have never experienced a RFH system with carpeting as a floor covering. I totally agree if you have tile, stone,and hardwood RFH is a deffinite compliment. I just can't recall a time when I walked across a carpeted floor barefoot, and it sent a chill down my spine. Probably one of those things if you don't have it you won't miss it. If you do have it, and its taken away you wonder how you will live without it.

Gordy

Gordy