in slab radiant floor heat Insulation??

Discussion in 'HVAC Heating & Cooling' started by Rolfsi, Mar 7, 2008.

  1. Rolfsi

    Rolfsi New Member

    Messages:
    11
    Location:
    Lacon Illinois
    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. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    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.
  3. Rolfsi

    Rolfsi New Member

    Messages:
    11
    Location:
    Lacon Illinois
    thanks

    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?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    hear

    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.
  5. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    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: Mar 10, 2008
  6. alternety

    alternety Like an engineer

    Messages:
    661
    Location:
    Washington
    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.
  7. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    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.
  8. seaneys

    seaneys New Member

    Messages:
    192
    Location:
    Chicago Suburbs
    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
  9. Rolfsi

    Rolfsi New Member

    Messages:
    11
    Location:
    Lacon Illinois
    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. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    radiant

    Now if it only heats properly.
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