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Insulation underneath radiant panel

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Simply Rad
Simply Rad Member Posts: 184
edited August 2016 in Radiant Heating
I have a project in the rough-in phase. We have a room that is raised and built over a suspended floor. The radiant panel flooring is about 2' higher than the framed subfloor. The contractor forgot to insulate directly under the radiant panel but the suspended flooring with have insulation. Should I worry about this very large airgap and have the contractor somehow insulate directly under the radiant panel or, which I think, will it work fine?
Thanks Jeffrey
Jeffrey Campbell

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  • SWEI
    SWEI Member Posts: 7,356
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    You almost certainly want to insulate. What kind of panel/piping is being used?
  • hot_rod
    hot_rod Member Posts: 22,132
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    Is the suspended floor well insulated? then a 2"air space with another framed floor? If well sealed around the edges the air space would be an insulator.

    Maybe spray or pour foam could be added to that space, if I'm understanding the build up.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    edited August 2016
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    It depends somewhat on the panel assembly. If the plates are exposed below, they could be radiating downward. R-13 kraft-faced batts are cheap.
  • Simply Rad
    Simply Rad Member Posts: 184
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    Basically there is a traditionally frame floor, and then another framed floor, about 2' total above this framed floor, with Warmboard on top. They forgot to insulated directly underneath the WB, but they will be insulating under the bottom subfloor. The space is insulated already on one side with spray foam insulation because its an outside wall. We could insulate the other side with batts, which is the inside wall. Hopefully I am explaining this so you can understand.
    Jeffrey Campbell
  • Firecontrol933
    Firecontrol933 Member Posts: 73
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    Two feet is too much IMO. The contractor forgot so I guess it's on him to figure out how he's going to get the insulation where it needs to be ...... and that's directly under the WB. Two feet is a lot more space than some crawlspaces I've had to work in.
    delta T
  • hot_rod
    hot_rod Member Posts: 22,132
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    The Warmboard will transfer heat energy to that 2' space below if left uninsulated. Probably there is loss around the edge of that space, so yeah it will add to the load.

    The floor covering R value on the WB will have some say on how much goes down also, not much R value in the plywood below the WB tubes.

    Is the space under the first floor heated? That lessens the load on that void space of course.

    Insulators are paid to work in tight spaces, I'd send them in and put as much in as the joist depth will allow, insulation is the gift that keeps on giving.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Rich_49delta T

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