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Radiant Floors below subfloor

RedMonte85RedMonte85 Posts: 11Member
Hi, I have recently purchased a home that is going to be completely remodeled. The house currently has baseboard water heat and the boiler is fairly new (Bosch ZBR35-3). The house is a one story ranch, 1600 sq ft with a full basement. I had some questions regarding radiant heat that would be attached in the bays between the joists, beneath the subfloor. I have read and read about the different methods and using the large aluminum plates to help disperse the heat.
1. How well do these radiant floors heat through a subfloor? I know that its most effective in a slab or directly under tile.
2. Will that Bosch boiler be enough for a system like that?
3. Will the radiant heat keep me from installing hardwood flooring?
4. Would vinyl flooring help soak and radiate the heat better?
5. I read in one of the threads on here about an outdoor switch or something that goes on the system, how exactly does that work? Does it regulate the boiler according to outdoor temperature?

I know its a lot of questions, thank you.

Comments

  • ZmanZman Posts: 4,997Member
    1. With aluminum plates, It will heat great through subfloor.
    2. Your boiler is almost certainly too big for a house that size. You would have to do a heat loss calc to be sure. It is certainly big enough.
    3. Hardwood flooring works just fine with radiant.
    4. Vinyl flooring will allow the heat to transfer more easily that other flooring. You should pick flooring you like, unless you like insulation for flooring, it will work just fine.
    5. Outdoor reset control (weather compensation control according to Bosch). Reads the outdoor temp and decreases the boiler setpoint temp as the the outdoor temp goes up. This improves efficiency and comfort.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RedMonte85RedMonte85 Posts: 11Member
    Thank you, as far as the installation goes for the radiant floor, what is better for the insulation of it? I have read that people insulate below the pex tubing, leaving an airspace, using foiled bubble insulation. I have also read about people using blow in insulation? Is there a preferred method and "best" insulation type to use?
  • ZmanZman Posts: 4,997Member
    If you use aluminum plates, you don't have to get too fancy with the insulation. The goal is to keep the heat from going down. I would use regular unfaced fiberglass. An airspace can't hurt, foil is not needed but many like to use it anyway.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RedMonte85RedMonte85 Posts: 11Member
    Is there a certain aluminum plate that works better than others? I've looked at the joist trak from uponor and there was another plate that had the long edges rolled for the pex to tuck into it, cant remember the name of it. Then there are the type that hold the pex directly against the wood subfloor and screw in over top of the tubing which dont seem as efficient to me. Joist trak looks the like the best to me, is that the case?
  • RedMonte85RedMonte85 Posts: 11Member
    I just would like to avoid any knocking sounds the tubing might make, guess I could always wrap parts of it with tape or something to make it fit more snugly
  • hot_rodhot_rod Posts: 11,684Member
    The extruded type will have the tightest fit, due to the additional material thickness and fillet. Of course more aluminum= more $$.

    PAP tube will have less expansion movement, but it is tougher to thread thru joists, holes, etc. without kinking.

    Many installers prefer 3/8" pex as it is more flexible, probably easier for DIYers or occasional tubers :)

    Some pex types market as more flexible, keeping the tube warm also helps with flexibility.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GordyGordy Posts: 9,264Member
    Zman said:

    If you use aluminum plates, you don't have to get too fancy with the insulation. The goal is to keep the heat from going down. I would use regular unfaced fiberglass. An airspace can't hurt, foil is not needed but many like to use it anyway.


    I’ve been thinking about the additional bubble foil step below the plates. Not for its supposed insulation, or reflective properties which are rubbish.

    I’m not saying it’s necessary, but I think it helps isolate the tube detail space from the fiberglass insulation, in not allowing convective currents that can occur in a fiberglass insulation batt.

    Fiberglass insulation batts are like a big air filter.
  • RedMonte85RedMonte85 Posts: 11Member
    I haven't read about PAP tubing, I will have to look into it. Is it more expensive?

    Will 3/8 tubing heat as well as 1/2"? I would assume that the plates for 3/8 would be cheaper?
  • RedMonte85RedMonte85 Posts: 11Member
    I wish there was a way to heat the basement through the ceiling as well, I will probably keep baseboard heat down there because I am not really willing to give up 3 inches of headroom on an already low ceiling
  • hot_rodhot_rod Posts: 11,684Member
    Yes the 3/8 will heat the same as 1/2, smaller diameter = shorter loop length is all.

    Consider installing radiant ceilings, and or walls in the basement. No real reason that radiant needs to be in the floor. It will need to be a separate install, the floor above will not work to heat up and down at the same time.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • RedMonte85RedMonte85 Posts: 11Member
    Well, the walls are concrete block in the basement, not sure how that would fair. I will have to run electrical through the joists below whatever insulation I put on top of the pex tubing for the floor heat. Not sure if sandwiching electrical in between hot tubing on the ceiling is a good idea even if there is a layer on insulation on both sides of the wiring
  • RedMonte85RedMonte85 Posts: 11Member
    I might have to think about the walls, would have to put it over furring strips and be mighty careful where screwing the drywall in
  • TimoteiyTimoteiy Posts: 1Member
    Hi RedMonte85. I did my house basement here with both 2 inch thick polystyrene insulation board glued on with PL300 and in some places also with furring strips R12 fiberglass before drywall. HUGE difference! I didn't have the central heating system in yet this last winter, we had over a month of -4, -5 Fahrenheit and all there was in a 600 square foot suite was an electrically heated kitchen floor 10' by 10', and it was very comfortable as long as doors were left open!
    I did another house retrofit for heated floors and used nailing strips (which helped level the cement) between the 1/2 inch pex, with metal plates where pex crossed over, THEN a 1/2" plywood floor THEN solid 5/8" hardwood. Crazy job. never again, but the heat came through fine. With the Burnham conventional boiler and improper controls it was way too costly to heat though. A friend built a brand new house with pex under the floors with the plates between joists, and an electric boiler and now he relies heavily on his wood stove to keep the electric bill down.
  • kenjohnsonkenjohnson Posts: 34Member
    I just finished a radiant floor install on a remodel. I went through the same thought process you are going through. You can read my post here - my be helpful.
    https://forum.heatinghelp.com/discussion/163346/would-like-some-feedback-on-my-radiant-design-plans#latest
  • RedMonte85RedMonte85 Posts: 11Member
    Hi again and thanks kenjohnson for that link, very informative. So I am just getting around to this heated floor. I did some heat loss calculation on the house. I completely gutted it and put in all new windows and insulation in the walls/ceilings. The house is well insulated and according to the slantfin calculator, I need 21,664 BTUs to heat the 1st floor of the house.
    I have not calculated how long my loops need to be yet. I figured I would be putting 4 loops in on the first floor. One for each bedroom and bathrooms (3 bedrooms and 2 baths) and one for the living area/kitchen combined.
    Is there software to use to calculate the loop lengths or is that something I just need to measure manually?
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