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advice on radiant tubing install

Adk1guy Member Posts: 60
edited November 2022 in Radiant Heating
I have an open kitchen/ hall area I am planning radiant tubing below the subfloor accessible from below in the basement. I have several questions I'd like to field. I realize a heat loss calculation is recommended but there is only about 300 linear feet of tubing space available if at 8" centers in the joint bays and I want to fill it in.

1. Heat under cabinets and appliances? Put tubing under them or not?
2. extruded $$metal plates like uponor or thin plates like omega? Will the extra expenditure on the thicker plates put more heat upstairs?
3. type A uponor vs type b?
4. Manifolds with flow meters upside down? Since the tubing will be going up, I will either need to route the tubing 180 degrees or mount the manifold upside down.


  • hot_rod
    hot_rod Member Posts: 21,804
    If you have a kitchen sink and dishwasher on outside wall, I would put 1 run, 6" off the outside wall area. Even if you have to drill joists to do it.

    It might be nice to get 3 tubes per joist space, the tight tube helps in small areas that might have high loads due to limited floor area. Tubing gets more complicated however.

    Extruded plates grip the tube best. Radiant Design has the ThinFin extruded plates, lighter and narrower, but same tube fit.

    Consider 3/8" pex A if you need to do a lot of threading, it is the most flexible. Mr Pex has always claimed to be the most flexible pex.

    Caleffi offers inverted manifolds, probably other brands will work if you can flip the auto vents.
    I have seen manifolds mounted up flat against the floor joists also.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kenjohnson
    kenjohnson Member Posts: 84
    1/2" is nice if you have a lot of runs and want to keep the pump size small for efficiency. It is a lot harder to bend and pull without kinking.

    I did not run my tubing under cabinets. Make sure not to run it under the refrigerator.

    You didn't ask, but just in case you think about doing three tube runs per joist bay - don't. You only get about 10% more heat output and it is a real pain-in-the-$#% to route the extra tubing.

    Be sure to diagram out you plate locations and tubing runs before you get started. Leave plenty of room for pex bends at the end of the plates.