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i need help of how many loop 1 or 2 between the joist bay

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lofi
lofi Member Posts: 2
good evening everyone,

Im working on my parents house, I remove the furnace to have more space in the basement and I want to install radiant system to the main floor through the joist.

so I did the calculation for the space and I will be running even number to all of the zone area. but I have one problem, in one of the area between each joist only 10.5 inch means 12inch OC so I can do one run per joist bay or still have to do 2 run per bay.


please help if you know. thank you in advance for helping

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  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    No. I don't think you can get two transfer plates in a 10" space. You might investigate if you can get a two track plate for two rows of pex on a single plate.
    lofi
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
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    Transfer plates are 4" wide. 3/8" PEX is usually installed on 8" centers. The plates can be trimmed for smaller joist bays. One loop per bay is usually the method.
    lofi
  • Alan (California Radiant) Forbes
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    You can also use Ultra-Fin which only requires one run per bay. 
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    lofi
  • Ironman
    Ironman Member Posts: 7,379
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    Rehau has these which are 9 1/2” wide:



    Have you done a Manual J heat loss calculation to see if a radiant floor will be sufficient to heat the house by itself? In most older houses it won’t.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Alan (California Radiant) ForbeslofiSTEVEusaPAZman
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    You'll notice that in the Rehau that the insulation under the plate has 1" of air space. The fibre glass insulation you might add is not pressed up against the plate. You need that air space.
    lofi
  • lofi
    lofi Member Posts: 2
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    thank you guys for helping me out.

    thank you Pual pollets, so from what i understood from your message I can install single loop of 1/2 pix pipe on single transfer plate and also Im gonna install insulation (as far as i know i have to leave a gape of 1 inch to 1.5 inch for air to flow between pix pipe and insulation but what type of insulation can i use inside the joist bay. also the R value should be 22!! or doesn't matter what's the R value. and any recommendation of what type of insulation to use.

    thank you again for your help and support.

    -thank you for the info, Ironman you asked "Have you done a Manual J heat loss calculation" nope i have not done it yet but i made some research about the topic and some people said I can use coolcalc. I will do it this weekend. let say it is not sufficient then i cannot install radiant heat floor?!
  • Ironman
    Ironman Member Posts: 7,379
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    You can install it, but if it’s not sufficient you’ll need some form of supplemental heat.

    SlantFin has a free app that you can download that’s fairly accurate.

    There’s a link somewhere on this site or you can google it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Alan (California Radiant) Forbes
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    From the Radiant Design & Supply website:

    Our ThinFin C is a thinner gauge and narrower plate than ThermoFin C. The heavier gauge ThermoFin C is 1/2" wider than ThinFin C and has 18% more contact area. ThinFin C may be sufficient for buildings that are not in extremely cold climates or for well insulated buildings. Also, if the space between your joists are narrow so that you have to install the two rows of fins 6" on center instead of 8" on center, then you will have more plates spaced closer and could use the ThinFin. Two rows of plates are installed between the joists to pull loops of tubing in each joist. With less aluminum, ThinFin is more economically priced than ThermoFin.

    https://www.youtube.com/watch?v=MdFTk5R6fFQ&t=25s
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    edited February 2022
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    One pex loop = 2 pipes. Pulling 1/2" pex is much harder than 3/8". Close the distance between the plates when joist bay is less than 15". If there's only room for one pipe and plates, run the return on the side of the joist. Min. R20 insulation which can touch the plate. No need for air space.
    Try the manual from Uponor: https://www.uponor.com/getmedia/e5fedcd0-6f25-425f-afe1-f34aa8f5e06e/quik trak design and installation manual?sitename=USA