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Author Topic: Radiant walls  (Read 6956 times)

wreckit87

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Radiant walls
« on: May 03, 2018, 06:32:24 PM »

Anyone ever experimented with radiant walls? My forte is radiant slabs and I've played with a few underfloor setups and radiant ceilings but never a radiant wall. I have been looking into it for my own basement in lieu of CI rads or baseboard to keep the area open, and had a customer call today wanting to do a floor overlay in his basement with an already 6'7" ceiling height so I suggested it to him also and he liked the sound of not having a 6'4" ceiling. I admittedly know very little about the whole transfer plates process, but it seems if a guy could notch the studs and fill the wall with transfer plates and X feet of tubing to be covered by sheetrock or whatever, should be able to heat the space similarly to an underfloor system. Mine at home will only require about 5k BTU to keep toasty, so I was kinda thinking of running a few loops of 1/2" down low, behind the wainscot, in the plates, 8" apart with a total loop of 250ish feet. Theoretically 1GPM should yield 7500 BTU at 15 degree delta T right? Or 15k at a 30 delta? Would be running boiler temp water through it and it'd only run when using the family room down there, otherwise the space stays 62-65 with no heat. Wall cavities have 2-3" of closed cell foam in them, so the majority ought to radiate outward and warm the space right? I'm really digging the idea if it works, hate to spend the money on radiant ceiling panels when the other route can be done at 1/8 the cost
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RSI

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Re: Radiant walls
« Reply #1 on: May 03, 2018, 06:48:46 PM »

How close to the surface would the pipes be? I would think there would be a lot more chance of a pipe getting damaged in a wall than a floor.

1gpm will put out almost 500 btu/hr per degree drop.
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E Yoder

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Re: Radiant walls
« Reply #2 on: May 04, 2018, 04:26:52 AM »

http://www.contractormag.com/radiant/wall-heating

Some very interesting reading. Because you can run hotter surface temps wall heating can really put out the heat. I think it's a really well held secret that should get used more. They're saying up to 50 btu's per square ft. of heated wall.
To avoid driving a nail into a pipe they recommend keeping it below 48" (no pictures down there), and taking precise measurements before drywalling. I'd take pictures too.
Should be able to run full temp water with no issues. I've toyed with the idea of drilling either top or bottom plate to fish a loop(s) of 1/2" pex into a stud bay, then cut a register just above the baseboard and up near the ceiling. You'd have a 7' tall convector. Should draw really well.  :)
« Last Edit: May 04, 2018, 04:55:16 AM by E Yoder »
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wreckit87

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Re: Radiant walls
« Reply #3 on: May 04, 2018, 04:48:49 PM »

Attached is a picture of my basement. It's got 1/2" rock on top and the bottom 39" was originally supposed to be pine T&G but I changed my mind and went with 1/2" laminate flooring planks. The back wall has the planks on aside from the top row, and I was thinking of running the tubing on the wall on the right. Should never have an issue with nails down there, save for base trim which I would just run the first loop 4" high to miss that. Basement total is 28x50 inside, and that open chunk on the right is 25ft long. Could add more on the left by the sawhorses if need be. To my immediate left is a bedroom that would get some too. Should transfer decent through those planks, not? Thin and fairly dense.
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E Yoder

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Re: Radiant walls
« Reply #4 on: May 04, 2018, 07:35:29 PM »

So I'm reading some #'s on heating help.com. seems like 100° surface temps =approx 50 btu's per square foot. And if the room is 8' wide would be approx 18.75 btu's per square ft. in that room. I don't know if full temp boiler water would get you 100° surface temps or not if you put a lot of loops in there.
Just rambling here..
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wreckit87

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Re: Radiant walls
« Reply #5 on: May 04, 2018, 08:32:05 PM »

One way to find out I guess..... Or maybe two, if someone else has tried it lol. I searched over on heatinghelp and even started a thread, within 2 hours a couple of the know-it-all veterans that apparently want nothing but to harass the idiots like me tried making me feel stupid for even asking such a question so I just deleted the thread. I read that 100* surface temp thread also, but haven't even a guess at what actual surface temp might be with 160 AWT so it's hard to say
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mlappin

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Re: Radiant walls
« Reply #6 on: May 04, 2018, 09:10:19 PM »

One way to find out I guess..... Or maybe two, if someone else has tried it lol. I searched over on heatinghelp and even started a thread, within 2 hours a couple of the know-it-all veterans that apparently want nothing but to harass the idiots like me tried making me feel stupid for even asking such a question so I just deleted the thread.

You sure you didn’t post on  Hearth?
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wreckit87

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Re: Radiant walls
« Reply #7 on: May 05, 2018, 06:00:28 AM »

Yup. I'm not on that one, way too many cooks in the kitchen over there thinking they know something. Definitely heatinghelp. Most over there are very knowledgeable and willing to help, although a lot of it is service related stuff or steam which generally doesn't apply to "us people" lol
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E Yoder

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Re: Radiant walls
« Reply #8 on: May 05, 2018, 06:19:47 AM »

Yeah, I watch heating help a fair amount. It does lean into the world of steam, but a pretty friendly atmosphere of people who want to help.

But on your wall heating idea I would almost run some tubing on the other side just to be safe and only hook it up if needed. The other thing is depending on how much airspace is between the insulation and drywall you may have some heat convecting higher up in the wall and actually get more surface area then just what the tubing is behind.
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wreckit87

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Re: Radiant walls
« Reply #9 on: May 05, 2018, 11:55:14 AM »

Yeah, I watch heating help a fair amount. It does lean into the world of steam, but a pretty friendly atmosphere of people who want to help.

But on your wall heating idea I would almost run some tubing on the other side just to be safe and only hook it up if needed. The other thing is depending on how much airspace is between the insulation and drywall you may have some heat convecting higher up in the wall and actually get more surface area then just what the tubing is behind.

That's kinda what I was thinking also. The exterior walls, as you can see, have a good 3" of air space and should convect upward (good or bad, not sure) but I think I will put the tubing in all available spaces and connect as necessary. Or just connect it all and slow flow if it's too hot, would be more balanced that way
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E Yoder

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Re: Radiant walls
« Reply #10 on: May 05, 2018, 01:11:33 PM »

The warm air in the wall cavity should spread the heat out so you can get more btu's with a lower surface temp. Which will take a bit longer to heat up but feel great once it's running. My guess anyway.
I've got the cold air return for my upstairs air handler running through a wall cavity down into my basement. The hot air coil for the upstairs is in the basement so I get a heated wall where the duct goes. It sends out a surprising amount of heat through the drywall, just with 120° air temps in the wall when the top unit is running.
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juddspaintballs

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Re: Radiant walls
« Reply #11 on: May 05, 2018, 01:34:05 PM »

I've got a 1985 basement and I was also considering doing heated walls.  To keep heat from convecting up, couldn't you just put a horizontal block of 2x4 in each stud bay (like a fire stop) to keep the heat in the bottom 4' of wall?
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E Yoder

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Re: Radiant walls
« Reply #12 on: May 05, 2018, 02:05:00 PM »

My guess is it would heat up quicker with it blocked off, but total output would be lower. ?

Wreckit, I bet you could push a loop up behind the drywall if there's enough gap, run the pex vertical, going across the stud only at one place. Would need an initial blast of pressure to purge..
« Last Edit: May 05, 2018, 05:13:43 PM by E Yoder »
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wreckit87

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Re: Radiant walls
« Reply #13 on: May 05, 2018, 06:19:13 PM »

I would fish the supply and return lines through behind the drywall, yes. But as for running the loops vertically, what would be the advantage to that? I want the heat down low if anything, and getting transfer plates stuck behind finished drywall would be near impossible. Maybe I'm not understanding what you're saying, but I feel like horizontal is the way to go in my case?
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hoardac

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