Radiant Floor Heat with 'Ledger Method'

[sdmuleman]

Looking to put radiant floor heating into my 2 upstairs bathrooms while I've got the floors completely torn up. I've already got a hydronic system installed, so this will run off the existing boiler. Since I've got the floors completely up and no access from below it looks like the recommended install method is to essentially embed the pipe in sand on a false ledger. (see link). Has anyone done this? I'm worried about thermal expansion and abrasive wear from the sand. I want to use copper piping since I have it and know how to make good joints already, but norm for this applications seems to be PEX. Not sure if that's cost or that PEX is really that much better. Specifically, PEX looks like it expands about 10 times copper, and while it being flexible probably makes expansion easier to accommodate, it also means a lot more motion to cause the pipe to rub, and I feel like the plastic would be more susceptible to erosion.

Thoughts?

https://www.radiantcompany.com/details/methods/legder/

 

[Provience]

how often are you actually going to be fluctuating the temperature in the room? the expansion and any expansion friction should be non-issues.

it isn't like you are going from freezing to boiling on a regular basis.

PEX seems like the thing to use, but i don't know enough about the cost vs heat transfer through the tube vs ease of install arguments.

plastic is less susceptible to erosion

what are your thoughts on aluminum plates instead of sand?

https://www.radiantec.com/research-and-development/study-of-heat-transfer-plates/

 

[ExWrench]

I trust PEX to last longer than copper in that application. PEX is crosslinked polyethylene (PE), close cousin to UHMW PE which is ridiculously abrasion resistant. Zero chance of galvanic corrosion also.

I may be biased, since a microscopic chunk of (what appears to be a shard of mill roller) steel ended up factory-embedded in a length of copper pipe that was installed in my kitchen ceiling 10+ years before that galvanic corrosion time bomb created a pinhole in that pipe. Granted, that's a one in a billion chance of failure but I'm skittish because I won the copper pipe defect lottery once, and would rock PEX everywhere I could out of spite.

TL/DR: fuck copper pipe up the ass sideways with a rusty shovel dipped in a bucket of AIDS . . . or not

 

[sdmuleman]

So my vision was that temperature would be controlled through a zone control valve the same way my baseboard heaters are set up, which means there'd be a number of cycles per day. Maybe that's not the right way to do it though? I certainly want to be able to turn it on/off since we're not like to be using the upstairs all that much, which means that it will cycle then at a minimum.

Read a lot of heat transfer plates, but they'd have to be fastened the bottom of the subfloor to be effective from what I understand, which is a bit hard when there's no access to the bottom of the installed floor. Bit thing with the ledger boards & sand method is that I can completely install the radiant system and then drop the subfloor on top. Doesn't seem like there's any way to do that using aluminum plates.

 

[Provience]

huh, seems odd the AL plates can't be installed from the top, but i honestly didn't look that far into it.

the temperature, even if you cycle it, isn't going to be enough to cause significant expansion. especially being upstairs, i'd be surprised if it actually does get below 50* and what s the water temp run, low 100's?

what kind of subfloor and topfloor are you putting over it? i'm learning myself so i'm more curious than helpful, sorry

 

[[486]]

I'd be scared of the copper more than the abrasive wear
the thing with the pex is that you don't have any joints at all under the subfloor

this on top of an existing subfloor or atop a slab?

 

[dave_dj1]

Do you have insulation under the floors? If not why bother with radiant at all? As far as cycling, one thing with radiant is you should set it and forget it. It works off of thermal mass and by the time you get it up to temperature (think most of a day) you will be spinning your wheels. Have you considered in floor electric heat? May be a better option.

 

[Provience]

Do you have insulation under the floors? If not why bother with radiant at all? As far as cycling, one thing with radiant is you should set it and forget it. It works off of thermal mass and by the time you get it up to temperature (think most of a day) you will be spinning your wheels. Have you considered in floor electric heat? May be a better option.

in floor electric is a terrible option if you are already set up for hydronic.

i agree about the thermal mass thing, which also depends on the floor and mounting. baseboard and radiators are quicker reacting than in floor.

 

[sdmuleman]

huh, seems odd the AL plates can't be installed from the top, but i honestly didn't look that far into it.

the temperature, even if you cycle it, isn't going to be enough to cause significant expansion. especially being upstairs, i'd be surprised if it actually does get below 50* and what s the water temp run, low 100's?

what kind of subfloor and topfloor are you putting over it? i'm learning myself so i'm more curious than helpful, sorry

THe function of the plates as I understand it is to spread heat from the pipe out and thence transfer to the floor. Thus they need to be firmly in contract with the subfloor and the pipe. Not sure how you could really do that without screwing the plates into the subfloor with pipe sandwiched between. I can think of ways it could be done, but none that are easy.

Currently planning 3/4 plywood, backer board and tile floor.

 

[sdmuleman]

;n222421]I'd be scared of the copper more than the abrasive wear
the thing with the pex is that you don't have any joints at all under the subfloor

this on top of an existing subfloor or atop a slab?

Neither. 2nd floor of an old house. I've got it stripped to the joists from above, but am leaving the first floor ceiling intact. The old flooring was hardwood T&G which was removed completely We're converting an old room to a bathroom. Didn't want a wood floor in the bathroom, needed to have it open for plumbing and also needed to harvest the wood to use elsewhere (filling in an old stairwell)

 

[[486]]

I'd look at the "gypsum concrete" option if you're worried about the sand abrading the tubing
you pour an inch thick slab that embeds the tubing

 

[sdmuleman]

Do you have insulation under the floors? If not why bother with radiant at all? As far as cycling, one thing with radiant is you should set it and forget it. It works off of thermal mass and by the time you get it up to temperature (think most of a day) you will be spinning your wheels. Have you considered in floor electric heat? May be a better option.

Will be putting insulation under the flooring. Joist depth is 8", so should have space for a few inches of insulation. Also, it's the second story, so leakage heat still goes into an occupied area of the house. Not the best, but better than leakage to a crawl space.

Driver for radiant is two fold - don't have space for baseboard radiator in the bathroom and the idea of a warm floor sounds nice. Certainly other options, but it seemed like a nice idea, I already have the boiler and rest of the system, and I'm already tearing the flooring down to bare joists anyway.

 

[sdmuleman]

;n222487]I'd look at the "gypsum concrete" option if you're worried about the sand abrading the tubing
you pour an inch thick slab that embeds the tubing

Interesting. I wonder if I could kill 2 birds and just that stuff as subfloor/tile base as well. That is, instead of plywood ledger ~2" below subfloor, sand/concrete, 3/4 subfloor, backer board & tile, just do plywood ledger then gypsum concrete to about 3/4" above top of the joists then and tile directly on that.

 

[Fullsize80cherokee]

The only way to go is pex and gypcrete.

 

[[486]]

Interesting. I wonder if I could kill 2 birds and just that stuff as subfloor/tile base as well. That is, instead of plywood ledger ~2" below subfloor, sand/concrete, 3/4 subfloor, backer board & tile, just do plywood ledger then gypsum concrete to about 3/4" above top of the joists then and tile directly on that.

dunno, gypsum really don't like water, though I suppose nothing does, really
hell maybe use 2" of normal portland cement mortar? it'd be a lot heavier though

 

[Provience]

Interesting. I wonder if I could kill 2 birds and just that stuff as subfloor/tile base as well. That is, instead of plywood ledger ~2" below subfloor, sand/concrete, 3/4 subfloor, backer board & tile, just do plywood ledger then gypsum concrete to about 3/4" above top of the joists then and tile directly on that.

i would be concerned going around the joists with a single pour

 

[Muckin_Slusher]

;n222421]this on top of an existing subfloor or atop a slab?

Atop a slab with joists???

 

[Fullsize80cherokee]

Interesting. I wonder if I could kill 2 birds and just that stuff as subfloor/tile base as well. That is, instead of plywood ledger ~2" below subfloor, sand/concrete, 3/4 subfloor, backer board & tile, just do plywood ledger then gypsum concrete to about 3/4" above top of the joists then and tile directly on that.

In this neck of the woods all the new houses I work on are 1 1/2” of gypcrete on top of the subfloor on any floor that isn’t on grade. Pex is stapled down then they pour gyp, if hardwood is going down on top they put some 2x4 runners down spaced about 12” apart so the hardwood can get nailed down

 

[[486]]

Atop a slab with joists???

for whatever reason people pour slabs in crawlspaces then set floor joists like 12" above them
retarded shit, but my house had an addition built like this

ETA: I mean to say having a crawlspace rather than just dropping the house onto the slab itself
not enclosing the floor which I like the idea of a lot after dealing with all the rot from an open crawlspace in the rest of that house

 

[Fullsize80cherokee]

Actually this is getting more popular too, all plumbers seem to hate it and it’s like black ice walking on it with snowy boots. Might be right up your ally

https://www.warmboard.com/warmboard-s

 

[Muckin_Slusher]

;n222505]

for whatever reason people pour slabs in crawlspaces then set floor joists like 12" above them
retarded shit, but my house had an addition built like this

Can't get in a 12 inch crawlspace? Fatty!!

My basement floor is framed (?) with 2x4s on the flat, then double layer of 5/8 OSB on top. When I bought the house I couldn't figure it out that when you jumped on the floor it felt concrete solid, yet couldn't be, since in parts I can see that the concrete floor was lower. Finally holesawed a core to see.

My place was built 1937 BTW, my walk out basement was originally a garage.

 

[[486]]

Can't get in a 12 inch crawlspace? Fatty!!

Can. Won't.

Ended up being a bunch of dead animal remains under there, I coulda easily been one if I got stuck. Also, hard to shoot at them in that tight of confines.

 

[dave_dj1]

in floor electric is a terrible option if you are already set up for hydronic.

i agree about the thermal mass thing, which also depends on the floor and mounting. baseboard and radiators are quicker reacting than in floor.

I agree but it would provide quick heat and relatively easy installation. I'm talking about the under tile stuff.

 

[Provience]

I agree but it would provide quick heat and relatively easy installation. I'm talking about the under tile stuff.

yeah, but the advantage of that stuff is that it is cheaper because you don't have to buy all the boiler and such and stuff. he's already got all the 'expensive' stuff running the rest of the house.

 

[Provience]

In this neck of the woods all the new houses I work on are 1 1/2” of gypcrete on top of the subfloor on any floor that isn’t on grade. Pex is stapled down then they pour gyp, if hardwood is going down on top they put some 2x4 runners down spaced about 12” apart so the hardwood can get nailed down

that's a thought. instead of doing a ledger, stuff some glass between the joints and subfloor, then pex/gyp/tile

use a rolled setupdown at the entry way to save the toes depending on the height difference.