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All-Purpose OWF Discussions => Plumbing => Topic started by: wreckit87 on May 03, 2018, 06:32:24 PM

Title: Radiant walls
Post by: wreckit87 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
Title: Re: Radiant walls
Post by: RSI 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.
Title: Re: Radiant walls
Post by: E Yoder on May 04, 2018, 04:26:52 AM
http://www.contractormag.com/radiant/wall-heating (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.  :)
Title: Re: Radiant walls
Post by: wreckit87 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.
Title: Re: Radiant walls
Post by: E Yoder 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..
Title: Re: Radiant walls
Post by: wreckit87 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
Title: Re: Radiant walls
Post by: mlappin 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?
Title: Re: Radiant walls
Post by: wreckit87 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
Title: Re: Radiant walls
Post by: E Yoder 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.
Title: Re: Radiant walls
Post by: wreckit87 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
Title: Re: Radiant walls
Post by: E Yoder 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.
Title: Re: Radiant walls
Post by: juddspaintballs 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?
Title: Re: Radiant walls
Post by: E Yoder 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..
Title: Re: Radiant walls
Post by: wreckit87 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?
Title: Re: Radiant walls
Post by: hoardac on May 06, 2018, 11:55:39 AM
http://www.contractormag.com/heating/hydronic-radiant-wall-heating-still-greatest-trade-secret-us

I would say yes.
Title: Re: Radiant walls
Post by: E Yoder on May 07, 2018, 05:06:47 AM
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?
I wasn't thinking you would use transfer plates with 160° water. Just heat up the air space with pex. I was thinking oval vertical loops crossing over the studs once to minimize the chance of hitting it with a nail.
Just ideas. No big deal.
Title: Re: Radiant walls
Post by: RSI on May 07, 2018, 06:39:58 AM
That would probably work ok on inside walls but seems like you would have a lot of heatloss if you run 160 degree water in an outside wall. I would think on outside walls you would want to use transfer plates and keep the temp as low as possible. Also, probably a good idea to put a radiant barrier behind the transfer plates to avoid losing too much radiant heat trough the wall.
Title: Re: Radiant walls
Post by: wreckit87 on May 07, 2018, 02:17:16 PM
That would probably work ok on inside walls but seems like you would have a lot of heatloss if you run 160 degree water in an outside wall. I would think on outside walls you would want to use transfer plates and keep the temp as low as possible. Also, probably a good idea to put a radiant barrier behind the transfer plates to avoid losing too much radiant heat trough the wall.

There's 2-3" of closed cell against the block and another 3" of air space behind the drywall, think the loss would be noticeable? The foam is always room temparature (and below grade, so ~55 degrees outside anyway), I guess I hadn't considered there being any noticeable loss to the exterior. Was kinda hoping whatever is lost through the plates would just convect up and warm the drywall above? Maybe I'm nuts
Title: Re: Radiant walls
Post by: mlappin on May 07, 2018, 08:38:01 PM
Watching close.

Kicked my self when we remodeled the bedroom, should have installed ultra fin then, didn’t hear of it till years later.

Still have the office to remodel, it shares a wall with our bedroom, I’m thinking place the pex, staple a layer of ply foil over the studs then cover the office side in drywall. The ideal of placing registers at the top and bottom also has merit. Fire stops are already in the walls and I tend to leave em, so only the bottom half of the wall would get heat anyways, I’d also stay at least a foot off the floor as we have the tall baseboards.

If it works may redo the upstair bedrooms the same, a lot easier than tearing the floors up to place ultra fin in the joist bays. Ain’t tearing the downstairs ceilings out just to install radiant, those were all over lays anyways as I wasn’t about to pull lathe and plaster down in my face.
Title: Re: Radiant walls
Post by: RSI on May 07, 2018, 09:42:12 PM
If you have 3" of air space I would put a layer of foil backed foam or bubble wrap against the foam. It doesn't cost that much and should reflect the radiant back into the room. I am guessing that the lower you can run the water temp, the less heat loss you would have without the radiant barrier. If you only end up needing to run 110 degree water then it may not make any difference.

Title: Re: Radiant walls
Post by: E Yoder on May 08, 2018, 06:13:12 AM
Watching close.

Kicked my self when we remodeled the bedroom, should have installed ultra fin then, didn’t hear of it till years later.

Still have the office to remodel, it shares a wall with our bedroom, I’m thinking place the pex, staple a layer of ply foil over the studs then cover the office side in drywall. The ideal of placing registers at the top and bottom also has merit. Fire stops are already in the walls and I tend to leave em, so only the bottom half of the wall would get heat anyways, I’d also stay at least a foot off the floor as we have the tall baseboards.

If it works may redo the upstair bedrooms the same, a lot easier than tearing the floors up to place ultra fin in the joist bays. Ain’t tearing the downstairs ceilings out just to install radiant, those were all over lays anyways as I wasn’t about to pull lathe and plaster down in my face.
I have this idea floating around in my head that on a retrofit / remodel job you could cut the register holes and drill down through the bottom plates into the crawlspace and pull pex up into the wall cavity and back down. Then install the register covers and you'd have a convector in a room that didn't have good options otherwise.
I hope I'll have time this summer to build something like that and tie it into the lines in my shop just to see how much airflow would start rising up through the stud bay.
Title: Re: Radiant walls
Post by: mlappin on May 08, 2018, 11:25:55 AM
Copper pipe would work even better.
Title: Re: Radiant walls
Post by: E Yoder on May 08, 2018, 11:41:03 AM
Yes, but I wasn't sure how to get it inside the wall.   :)
Title: Re: Radiant walls
Post by: sceptre74 on September 26, 2018, 05:39:11 PM
I know a been a while since this post has been active, but I just came across it and I'm intrigued.
I had a flood in the basement this summer and had to gut the flooring and 2 feet of drywall at the bottom the walls. I didn't have any heat down there but was planning on putting a baseboard heater in each you this time around. Then I came across this thread. Now what I'm thinking of doing is run one loop of 1/2" pex within the 2 feet of space and put insulation just above it to keep the heat from rising within the wall. My question is would 180 degrees water be too high? I have no way of dropping it and figured with the one loop the higher it is probably the better it would be.
Title: Re: Radiant walls
Post by: wreckit87 on September 26, 2018, 08:54:22 PM
I actually did a couple radiant walls for customers this summer with awesome results. Haven't gotten to my own yet but it's coming. Output on a single loop in 2 feet will be pretty low though, and 180 degree pex will turn into wet spaghetti- ask me how I found out. How would you plan on zoning this basement if you have no means of knocking temp down?
Title: Re: Radiant walls
Post by: sceptre74 on September 27, 2018, 03:10:45 AM
The basement is half finished with 2 bedrooms and no plans to finish the rest. There is plenty of heat from my primary secondary loops to heat the rest of it that is wide open to it. My plan is 1 circ for the entire loop.
Title: Re: Radiant walls
Post by: wreckit87 on September 27, 2018, 05:52:48 PM
So you'd just run it 24/7 with your boiler circ? I'm confused
Title: Re: Radiant walls
Post by: sceptre74 on September 27, 2018, 06:18:46 PM
No, it would be a secondary loop off of the primary one. I have a heat exchanger separating the owb from the house install. I also have a taco sr504 exp controlling each loop. When I built my system I added some extra tees in case I wanted to add more Heating devices.
Title: Re: Radiant walls
Post by: wreckit87 on September 29, 2018, 06:58:39 AM
Gotcha! I really don't think you would like running 180 through there. The linear expansion and noise is enough to drive a guy batty. Pex-Al-Pex will help considerably with that, but it'll still be noticeable if you're trying to keep them straight and/or sandwiched. How long are these walls? The BTU output is pretty minimal and takes a whole lot of tubing. I took a course with Uponor this summer and was trained in their Quik-Trak system, and must say I was very surprised with how little the output really is. And sheetrock cannot withstand anything over 130* water without warping and cracking, so that limits a lot of output also. As for knocking your temp down, if you'd be adding a pump for this loop anyway, why not just pipe a mixing valve in between the primary and circulator? Then you have whatever temp water you need
Title: Re: Radiant walls
Post by: sceptre74 on September 29, 2018, 06:17:20 PM
I guess  I could add a mixing valve but it looks like going this route was just wishful thinking. Lol. Guess I'll be installing baseboard heaters instead. What size do you think I'd need for a 175 sqft room?
Title: Re: Radiant walls
Post by: wreckit87 on September 30, 2018, 08:08:06 AM
175? Small. That size space with average insulation in my neck of the woods would only take about 2000 BTU, so a 6 foot section of 3/4" with 180 degree water would be plenty
Title: Re: Radiant walls
Post by: sceptre74 on September 30, 2018, 12:45:03 PM
Good. Thanks for the help.
Title: Re: Radiant walls
Post by: mlappin on July 16, 2019, 11:22:45 AM
Gotcha! I really don't think you would like running 180 through there. The linear expansion and noise is enough to drive a guy batty. Pex-Al-Pex will help considerably with that, but it'll still be noticeable if you're trying to keep them straight and/or sandwiched. How long are these walls? The BTU output is pretty minimal and takes a whole lot of tubing. I took a course with Uponor this summer and was trained in their Quik-Trak system, and must say I was very surprised with how little the output really is. And sheetrock cannot withstand anything over 130* water without warping and cracking, so that limits a lot of output also. As for knocking your temp down, if you'd be adding a pump for this loop anyway, why not just pipe a mixing valve in between the primary and circulator? Then you have whatever temp water you need

So if I read this correctly, even using the quik-trak on a wall the temp will need to be mixed down to 130 or less?
Title: Re: Radiant walls
Post by: wreckit87 on July 16, 2019, 03:19:48 PM
Depending on finish, maybe. I'd have to look in the paperwork but I want to say the max temp for Quik-Trak was 140