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Old 09-18-13, 12:07 PM   #1
Daox
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Default Hydronic floor heat spreader plate options

I am thinking a bit ahead in my office remodel. I am definitely doing a hydronically heated floor to go along with my solar hot water system. I am thinking of going with 6" on center either 3/8" pex or 1/2" pex tubing with aluminum heat spreaders to increase efficiency. The floor will not be poured concrete, but wood between the pex tubing.

So, what are my options for heat spreaders?

Obviously there is the DIY route. Buy a bunch of aluminum and cut it and form grooves in it. This is definitely going to be the cheapest route. Builditsolar has a pretty good selection of info on how to make these heat spreaders here:

Making, buying, and evaluating heat absorbing fins for solar collectors


But, what if I don't have time to make heat spreaders, or I'm just lazy and don't want to? What if I'm just looking for the absolute BEST heat spreader available? What are my options now? I'm pulling links from the builditsolar page above, but here is what I have:

UP Solar Solutions:
Aluminum Solar Absorbers - U.P. Solar Solutions

This seems like a DIY friendly place to work with. They are .017" thick. They make fins for 1/2", 5/8" and 3/4" PEX. You can order the exact quantity you want/need!


RHT Heat Transfer Plates:
RHT Heat Transfer Plates

Slightly less costly than the above option (in the .019" variety). .019" thick, and .024" versions. They also offer heat spreaders for 3/8" PEX. However, you have to buy in boxes of 100 pcs.



What other options are out there? What have you guys done yourself?

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Last edited by Daox; 09-18-13 at 01:09 PM..
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Old 09-18-13, 01:24 PM   #2
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Daox

I wonder if a spacing of tube 6" placed in a plywood groove with a ceramic or porcelin tile thin-set down would conduct heat well enough without an aluminum spreader. I know that a floor-cover of tongue and groove wood would be useless or god forbid carpet but I would bet that a hard surface such as for-mentioned tile would act more like the Cadilac concrete slab.

Maybe some one could try an experiment with a small section to see how well the heat would propagate through the tile.

Randen
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Old 09-18-13, 01:48 PM   #3
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I will be using bamboo over the PEX tubing. Its about 5/8" thick.
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Old 09-18-13, 06:41 PM   #4
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Look for the REHAU plates. They are very easy to install and you need only one per joist pace if you want 8" spacing but they don't have one for 6" spacing. That said, I have my tubing at 6' spacing in gypcrete between 2x2 at 12" centres and bamboo on top. works great.
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Old 12-13-13, 08:19 PM   #5
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Just as a follow up, I ended up going with the RHT plates. They came in and they're actually 4.75" wide. Its not a big deal, but it is 1/4" shorter than what the website says which is good to know when you're laying out your floor.
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Old 12-13-13, 11:35 PM   #6
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Quote:
Originally Posted by Daox View Post
...I ended up going with the RHT plates...
I didn't notice this thread until just now.

FYI:

I was looking into several different options, among them were Warmboard and Roth Panel. Warmboard is a pre-routed panel covered 100% with aluminum that is .020" thick, 12" spacings. Roth panel is a preformed high density styrofoam panel with 100% covered aluminum .020", 9" spacings.

Both are frightfully expensive.

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Old 12-14-13, 12:25 PM   #7
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Quote:
Originally Posted by randen View Post
Daox

I wonder if a spacing of tube 6" placed in a plywood groove with a ceramic or porcelin tile thin-set down would conduct heat well enough without an aluminum spreader. I know that a floor-cover of tongue and groove wood would be useless or god forbid carpet but I would bet that a hard surface such as for-mentioned tile would act more like the Cadilac concrete slab.

Maybe some one could try an experiment with a small section to see how well the heat would propagate through the tile.

Randen

Randen,

Good thoughts.

"Thin set" can be a variety of materials. Some are mostly concrete based where others have a lot of room temperature hardening plastics. Each would vary with the concrete type being the best conductor of heat.

I believe that a good thick (~ 1/2 inch; 1 cm) trowel of concrete based thin set would be a superb distributor of heat when directly coupled to a ceramic, tile, slate, stone or other type surface.

That said, a routed groove in the plywood would be an easy thing to do so that about 1/3 of the PEX pipe is exposed above the plywood surface (5 mm?). The thick layer of mud (thin set) would cover this and the tile could be applied rather easily on top of that.

It also depends on the heating system capacity and the number of degree days you are in. Here is Oklahoma, we use a thinner slab when we put in radiant flooring as it is easy to get a floor that contains too much heat. Our outside temperatures get cold quickly, but then warm up almost as fast. Home air temperature overheating is an issue here when well intentioned homeowners set their slab radiant to 78 F. It is great on cold nights, but when it warms up outside the next day, the heat remains in a thick slab for days (long thermal time constant). This heats air and clients have been known to open doors and windows to vent extra heat in winter.

Despite recommendations to keep the slab at 72-73 F, some insist on pushing the slab temp higher. And then they complain of overheating . . . This is especially true when the radiant system is a natural gas boiler with a huge BTU capacity.

The use of a small heating system (like geothermal) can be coupled to the slab so that the slab is heated in the daytime and the cumulative amount of stored BTUs delivered at night (thermal "flywheel" effect). This often requires a thicker slab (long thermal time constant). This allows a smaller heating unit to maintain a house temp on a cold night when double the number of peak BTUs might be needed.

The issue of how much slab thickness (how much stored slab heat) and how much heat to store is an evolving art.

It might be appropriate to put one long thermal time constant heated slab radiant system in a lower floor with faster responding (smaller time constant) floor above (bedroom areas).

That way, you may get the best of all situations where different living areas can be controlled more appropriately.

Easy to do with a variety of flooring materials.

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Last edited by stevehull; 12-14-13 at 12:29 PM..
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Old 12-14-13, 01:06 PM   #8
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Look up Gypcrete or Firmfill. Both are pourable self leveling gypsum based over pours that are used for floor heating all the time. They will feather down to 1/8" without cracking.

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