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Thread: in slab radiant floor heat Insulation??

  1. #1
    DIY Junior Member Rolfsi's Avatar
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    Default in slab radiant floor heat Insulation??

    What is the best product to use for insulating in-slab pex? Rfoil bubble or EPS Foam? Anyone have any experience with either?
    Thanks for your help.
    Rolfsi

  2. #2
    In the Trades Bob NH's Avatar
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    You don't usually insulate the PEX. You insulate between the slab and the ground and around the perimeter with a good closed-cell foam designed for the purpose. Then the heating tubes are usually installed about 1/3 of the thickness of the slab from the top.

    The fact that you are asking that question here suggests that you need more help that we can give you, because we don't know the details of your situation. A good design requires enough information to do the design and analysis.

    You need to get a good thermal design of the whole slab system. If you get it wrong you end up spending a lot of $energy$ to heat the earth. Then, when the energy costs become unbearable you are forced to abandon an expensive system and replace it with another expensive system that doesn't send a lot of BTUs toward the center of the earth where it is not needed.

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    DIY Junior Member Rolfsi's Avatar
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    Bob:
    Thanks for your help. I am assuming your answer to the question is EPS ridgid board? I would prefer to do the PEX aspect of it myself and leave the manifold, pumps, boiler, etc. up to a plumber. Any suggestions?

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    Moderator & Master Plumber hj's Avatar
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    Why would you want to do the most important, and the one that could be screwed up the easiest, and leave the easy part to the professional. If you do not install the PEX properly, or have the right PEX, you will have a bad system, no matter how good the plumber installs the rest of it.

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    Computer Programmer Bill Arden's Avatar
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    I have 2 inch yellow foam under the slab and 2 inch yellow foam up the outside of the slab.

    Edit: if you have a high water table, you will want 4 inches of ridged closed cell foam.
    Last edited by Bill Arden; 03-10-2008 at 09:39 PM.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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    Like an engineer alternety's Avatar
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    And you should put in and overlapped at the joints (glued is best) poly vapor barrier.

    You should look at some radiant heating books and figure out what size pipe (1/2" is pretty common). Make sure it has an oxygen barrier, layed out in the proper spacing and pattern, equal length loops if possible (makes balancing easier), manifold locations planned, zones figured out if you are doing that. It is not rocket science, but it does require knowledge.

    Web site for slantfin has a free heating loss calculator.

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    Computer Programmer Bill Arden's Avatar
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    I was lazy and let the heating contractor work all that out for the slab.

    This just leaves the easy parts that can be changed if needed.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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    DIY Senior Member seaneys's Avatar
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    Quote Originally Posted by Rolfsi View Post
    What is the best product to use for insulating in-slab pex? Rfoil bubble or EPS Foam? Anyone have any experience with either?
    Thanks for your help.
    Rolfsi
    I don't know if it is best, but I used 2" pink foam and a vapor barrier.

    Bob is right - you want really research this (especially if you live in a cold climate). As I recall, there are several good sites on the web.

    Steve

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    DIY Junior Member Rolfsi's Avatar
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    Default radiant heat

    Just finished getting it installed and boy is it neat. Used a Munchkin contender boiler and it is really a neat system.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Default radiant

    Now if it only heats properly.

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