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Thread: Radiant under thick slab...

  1. #1
    DIY Junior Member James20721's Avatar
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    Dec 2008
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    Default Radiant under thick slab...

    I came to this board because it seems to be open to thinking outside of the box.

    My house is over 100 years old and my family room is a converted concrete and brick porch that has been enclosed and insulated with r-13 walls, r-30 ceiling, and r-10 over the brick interior wall. I have a 7000 BTU Slant Fin baseboard on one wall. It can not keep up when the temps fall below 40 F.

    Below the room I have 4 crawlspaces with doors to the outside. My slab is 7" thick but I have taken spot reading with a non-contact thermometer and the temps over the basement are 4 degrees warmer than over the crawlspaces so I know that the slab is responding to the warmer basement. I know it will takes days to heat it but it would stay warm all winter.

    So, I'd like to install slant fins on the ceiling of the crawlspaces below the slab. I would also insulate the top 6" of the sides wall and 4" of rigid foam below the fins to force the heat up into the slab. I don't want to heat the entire crawlspace; just the slab. I plan to operate the system from November from March which is when I have my boiler running each year. I don't want the crawlspace to ever call for heat. I prefer for the water to flow only when the house calls for heat. However when the slab is warm enough, I want the flow to bypass the crawl spaces and continue back to the boiler. Imagine a sensor that would read the temp of the slab and only open the a valve when the floor is below the set temp.

    I'd like ideas on how to control the flow and suggest parts and components.

    How can I make this work to supplement the baseboard?

    Thanks,

    James
    PS: I will be in class all day. I will check the board later this evening.

  2. #2

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    James check out this website www.radiantec.com call one of their techs/engineers they are great for answers......Hope this helped ....Good luck..
    Last edited by smokinjoe; 12-15-2008 at 10:34 PM.

  3. #3
    Plumber in Previous Life sixlashes's Avatar
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    You have a typo smokinjoe, it is www.radiantec.com. I agree, they are knowledgable and willing to help.

    Applying heat to the outside foot or so of your slab will help. Is there any insulation on the exterior edge of the slab itself? That is critical. If you heat the slab like you are proposing, but do not have at least 2" of edge insulation, you will be fighting a losing (expensive) battle. More is better. I would also be careful with the clearances of the heater so you cannot heat the foam and cause odors.

  4. #4
    DIY Junior Member James20721's Avatar
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    The floor does not have any insulation at the moment. I will add 2" insulation around the sides and 4" under the radinat heat tubes. How much space should I have below the tubes. The 2" rigid insulation is rated for 190F. I did not think about odor. Thanks for the tip.

  5. #5

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    Quote Originally Posted by sixlashes View Post
    You have a typo smokinjoe, it is www.radiantec.com. I agree, they are knowledgable and willing to help.

    Applying heat to the outside foot or so of your slab will help. Is there any insulation on the exterior edge of the slab itself? That is critical. If you heat the slab like you are proposing, but do not have at least 2" of edge insulation, you will be fighting a losing (expensive) battle. More is better. I would also be careful with the clearances of the heater so you cannot heat the foam and cause odors.
    Thank u ..Corrected now

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