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Can one use a slab-over-slab radiant heat system?

pkbirchbay | Posted in Mechanicals on

Thank you all that answer my question.
Here is my question in short form:
Pole barn that was built as a small factory to be revamped to a new business and add radiant heat?

Can one add the heat system on the current slab and re-pour a new slab on top, where height and doors are not a issue? or Should one cut out the old slab add needed equipment and re pour a new slab. Again or Could new construction be a better option? Time and cost factors are important.
As a added note this is in mid northern Minnesota.
If you need more just ask. Thank you again!

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  1. Expert Member
    Dana Dorsett | | #1

    In your climate you'd want at least R12 under the slab if it's going to be the space heating radiator, R15+ even better. If you can afford to lose the headroom it's fine to lay down 3-4" of EPS and pour a new 4" slab over it.

    If the intended use for the building doesn't require concrete floors you could do it with 3-4" EPS and a wooden subfloor, using an above-the-subfloor approach such as WarmBoard or Roth Panels.

  2. GBA Editor
    Martin Holladay | | #2

    Q. "Can one add the heat system on the current slab and pour a new slab on top, where height and doors are not an issue?"

    A. Yes. However, you should know that the most important thing is how much rigid foam you have under the heated slab. If your existing slab lacks a continuous horizontal layer of rigid foam under the slab, then you would need to install about 4 inches of rigid foam above the existing slab, followed by a new slab that includes embedded PEX tubing.

  3. pkbirchbay | | #3

    Thank You for the answers: In theory I thought it was a sound idea. But just wanted to ask someone whom has more expertise than I.
    So In theory What is the best R factor I could get is 4 " of foam enough I have feet of overhead that is unneeded and unwanted but not cost effective to lower ceiling
    And a stranded pex layout for this area. with 4" of over pour. Building is being converted to dog kennels and boarding/Grooming/Runs. anything else I should consider?

  4. GBA Editor
    Martin Holladay | | #4

    If you use XPS, then your 4 inches of rigid foam will have an R-value of R-20, at least for the first few years. (R-value of XPS gradually declines, settling down eventually at about R-4.2 per inch after a few decades.)

    If you use EPS, which is much more environmentally friendly and is the preferred approach used by green builders, you'll have R-16 or perhaps a bit more.

  5. GBA Editor
    Martin Holladay | | #5

    Concerning your PEX layout -- you either need to hire an engineer or an experienced designer of hydronic heating systems.The first step is to perform a heat loss calculation (also known as a Manual J calculation) for your building.

    If you want to become a hydronic system designer, there's a lot to learn. Start studying on the web if you want -- but be aware that many websites include misinformation.

  6. dinnerbellmel | | #6

    Look up Crete-Heat panels. You can always add a low of foam underneath them for additional insulation.

  7. pkbirchbay | | #7

    Thanks for the answers. To anser your question I went to school for radiant heat systems am a engineer and have done design on some system to include the house I live in. But it is a very good point. There is a lot to know and you always learn more as time goes on.

  8. user-2890856 | | #8

    Ken ,

    How high is the ceiling in this structure ? What kind of temperature will you be trying to maintain ? Are there large barn doors , roll up doors ? How are the walls of the building insulated ?
    Where in Minnesota are you ? By any chance did you receive radiant training from Uponor ?
    Martin certainly offered a pertinent warning about mis information on the internet . I would offer that you make inquiries if needed at or the RPA website , both are well established with educated commentary from posters on heatinghelp that is all encompassing from the tubing layout and placement to how to optimize heating sources from renewables to boilers and or water heaters that are actually up to the task and can perform 2 jobs very well .
    That heat loss will be necessary and remember that dogs are lower to the ground and have different physiology than humans , not sure how far you want to go with design .

  9. pkbirchbay | | #9

    Richard: All very good points. To answer your questions.
    This building is in Hinckly Mn
    1.The ceiling is 10 feet spry foam walls The only door will be More of the style of a home it is getting all new windows.
    2. I did get my training at Uponor about 10 years ago.
    4. I an doing the design and then will run it by someone that does it much more often than myself.
    5. I will be subbing the job out but want the basic design before I request bids.
    6. it will be used as kennel and grooming so the temp will be to suit dogs. I plan to zone it out for different areas to custom needs per area.
    But any advice is very welcome
    Thank you.

  10. user-2890856 | | #10

    Do you have a proposed floorplan yet ? Would like to see it . Floorplans tend to shed lots of light on opportunities in design that benefit any type of structure , both animals and people benefit greatly from their varied needs for COMFORT . Wet dogs , dry dogs , dogs at rest , active awake dogs . How many BTUh does a dog produce , yep , lots of variables .

    What type fuel is available or are you considering ?

    Who was training when you were at Uponor 10 years ago , John Barba , Steve Swanson or Wes Sisco ?

    You might consider contacting Aune Plumbing in Zimmerman . Eric is quite possibly one of the best in Minnesota , Period ! He also is one of the principles at . He may be interested in a project like yours . If there is anything I may assist with feel free to contact me at [email protected] or by phone at 732-581-3833 .

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