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Pex and insulation for radiant ceilings

Hello All,

New to the forum.

I have a major renovation and addition starting on a home in New Jersey.
We are installing radiant heat under the floors in most of the existing home. We do not have access to the floor below the master bedroom but the ceiling in the master with be all open.

I see some specialized systems in the market for radiant ceilings.
Is it possible to run hydronic PEX loops in the ceiling to heat the master bedroom?
If so what method of insulation and airspace above the loops and/or heat transfer plates would be best?
Ceiling will be standard 5/8 sheetrock.

Thanks for your comments.


  • Rich_49
    Rich_49 Member Posts: 2,766
    Is the space above the master heated or unconditioned ? Insulation is a must regardless but what R value may be different .

    I have yet to see a room which radiant ceiling could not heat while , oddly enough ( not really ) , I have come across many rooms where floor heating required supplemental while moving it to the ceiling only eliminated that requirement .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Gordy
    Gordy Member Posts: 9,546
    There are a few ways to go about the assembly. I like panels with a continuous aluminum skin. Roth has choices of 3/8”, or 1/2” pex, and 12”, 6” tube spacing.

    Then there is plates with furing strips. I personally think it’s a little harder to get good contact to the back of the gypsum board for good heat transfer.
  • SENWiEco
    SENWiEco Member Posts: 159
    Do you have access to John Siegenthaler's Modern Hydronic Heating book? He talks about options and designs in chapter 10.17 (pg 471). It is very doable, I will be heating and cooling my whole house via ceiling panels made up of pex loops in ThermoFin C plates
    Sean Wiens
  • bob eck
    bob eck Member Posts: 930
    Can you put the radiant on top of your sub floor. Viega has a product called Climate Panel goes on top of the floor then the finished floor goes on top of it. Check it out.
  • TAG
    TAG Member Posts: 755
    We had electric ceiling at a beach house at the NJ shore when I was a kid -- believe it was buried in the plaster vs under drywall. Mention because It was quite common on LBI. Remember manuals with calculations years ago when I was looking into various radiant. You may want to track some down for basic numbers.

    It worked very well -- can remember laying in bed and feeing the heat. Have done wall radiant when I needed some supplemental heat when renovating .... in those situations I used foil foam and cut the foam to fit between the studs -- tubes attached to the foam ... works very well. Always do some in my showers.

    I have no numbers to back this up -- but the transfer through the drywall with tubes alone seems better than what you get with plates through subfloor and 3/4 finished wood with same temp water.
  • Gordy
    Gordy Member Posts: 9,546
    Believe it or not wood is a better insulator than gypsum.
    5/8 gypsum which is r .56. So unless you do over the top with a tile overlay, the ceiling would push through less r value than an over the top with wood, or even radiant friendly carpets.

    The chase copper, and brass manual from the old 50’s house quoted 70 btus a SF possible, With water temps of up to 160* :) . I don’t know if I’d ever push plaster to that temp, but they tested, and believed it to be possible. Never needed to though.
    Drywall puts an upper limit of 120*. I couldn’t imagine needing that kind of surface temp with a well designed panel.
  • hot_rod
    hot_rod Member Posts: 21,874
    Here is a simple DIY radiant ceiling detail.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gordy
    Gordy Member Posts: 9,546
    hot_rod said:

    Here is a simple DIY radiant ceiling detail.

    While nice workable panel detail I look at labor costs of doing a multi layer, and fastener system.

    1 layer of osb.
    1 layer of foam.
    1 layer Attaching plates
    Extra fasteners for each layer.
    1 layer of gypsum.

    With something like Roth, or similar.
    1 layer of Roth panel.
    1 layer of gypsum.
    Also the continuous aluminum skin is superior to the plates.
  • TAG
    TAG Member Posts: 755
    edited February 2019
    I have never used the Roth -- it's foam correct .. w/ AL skin?

    It's been a while since I looked at it and I was afraid of putting the wood over the foam w/ long nails (noise) .. Went with Warmboard. They sent me a sample --

    On a ceiling -- The Roth looks like a great idea. It was much cheaper vs warmboard
  • Gordy
    Gordy Member Posts: 9,546
    edited February 2019
    There’s is also sunboard. Which offers different tube centers. That’s what I like. With WB you are stuck with 12” centers which is fine, but depending on load it’s nice to have a tube center option.

    I think the foam insulation is redundant, and in that particular detail, maybe using foil face in trying to leverage that foil into the output spread.

    I think continuous aluminum is superior.
  • TAG
    TAG Member Posts: 755
    I thought the Roth was a full AL clad -- my memory is the panels are light weight. Think in a ceiling the foam and light weight would both be a plus ... no ?

    Never used the sunboard -- not a good website.

    Have had excellent results with Warmboard and wood floors .... it makes for an incredibly strong solid floor.

    Depending on insulation -- the OP's load my be low.
  • RetrosPex
    RetrosPex Member Posts: 56
    This is a very interesting discussion. I looked at Siggy's design, and I like it except for the detail about leaving one side of an aluminum plate loose to expand. I'd use extruded plates, and fasten them with coarse screws. Or, like Gordy says, use a panel with continuous aluminum. You cannot beat that. They will outperform a floor system. The other aspect I really like about a ceiling system is this: How many times have you changed what is on your ceiling? How many times have you changed flooring? Having it above head eliminates future issues with someone driving a nail thorough it.

    In my current project, I have a master bedroom heat plan that is yet to be decided. I purchased a couple European wall radiators, but planned to also go with underfloor plates. I'm considering putting a 2" layer of rigid insulation on the underside of the ceiling, screwing on plywood, and then applying plates. I'll also look into those panels Gordy mentions. Haven't seen them yet.

    The ceiling option sounds great. Good luck