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Radiant Ceiling Build Sequence

SENWiEcoSENWiEco Member Posts: 107
Hey folks,

I have finally finished my dwelling to the point that I am ready to plan the installation of the radiant ceiling panels and am having a lot of trouble visualizing the work sequence.

I will be utilizing the panel construction shown in Siegenthaler's Modern Hydronic Heating handbook per attached.

But how can you sequence the layers?

The floor truss bays will be insulated with 3-1/2" of mineral wool insulation. Then OSB will be attached to the bottom of the trusses. Then 3/4" rigid foam strips will be glued in place between Thermofin U transfer plates.

Here's the issue, this all needs to be done prior to starting the installation of the pex tubing, but by this point it is too late to run the pex leaders from the panels areas back to the manifolds.

The only way I can see doing it is to run the leaders to the area of the panels prior to insulating and then have a splice/joint in the tubing at the entry location of the panel. I know you are never supposed to have joints in concrete panels, but is it acceptable to have joints in ceiling panels (since they would always be reasonably easy to access down the road in case of an issue).

If not then ???

Appreciate any insight from those that have worked with ceiling panels.

Once I get this figured out I then have to determine a way of installing 200+ wafer style ceiling LED recessed light drivers through all of the above in a way that will satisfy the electrical inspector. :-(

Take care and stay safe!


Sean Wiens


  • STEVEusaPASTEVEusaPA Member Posts: 4,737
    Why not use warmboard on the ceiling? I wouldn’t use that drawing.
    Plan ahead, rough wire for lights.
    Warmboard, drill holes for wafer pucks.
    Run tubing.
    Drywall ceiling, then walls.
  • SENWiEcoSENWiEco Member Posts: 107
    thanks @STEVEusaPA - warmboard does not have my required spacing for one reason (I am going with 6" centres), but even if I did, there would still be the same question as to build sequence. Once the floor joists are covered over with some form of paneling, then it is too late to run the leaders back to the manifolds.

    As for the lighting, it is not as simple as just 'roughing in'. The inspector want the remote driver case for the puck lights roughed in and attached to framing. BUT the lead from the driver box to the puck on the lights I am using is not long enough to reach through 3-1/2" of insulation and the 1-3/4" of OSB/insulation/drywall. So I will need to get approval to just install the electrical cable whips into the floor assembly and then later once the ceiling is complete, pull the whip down through everything, connect the driver box and then just push loose up into the ceiling.

    Out of interest, what is you concern re the proposed drawing.
    Sean Wiens
  • BillyOBillyO Member Posts: 250
    edited September 2020
    viega climate panel
  • psb75psb75 Member Posts: 313
    what about remote manifolds near the room with ceiling heat?
  • SENWiEcoSENWiEco Member Posts: 107
    @BillyO - thanks but not a fan of the viega product. Expensive, plywood does not provide any insulative value, and the system only uses 3/8 tube.

    @psb75 - I am using 100% ceiling panels for all space conditioning and have 2 manifolds per floor that all the circuits are brought to.
    Sean Wiens
  • SENWiEcoSENWiEco Member Posts: 107
    Does anyone have guidance on how to install the leaders per my opening post?
    Sean Wiens
  • Alan (California Radiant) ForbesAlan (California Radiant) Forbes Member Posts: 2,626
    edited September 2020
    The only way I can see doing it is to run the leaders to the area of the panels prior to insulating and then have a splice/joint in the tubing at the entry location of the panel. I know you are never supposed to have joints in concrete panels, but is it acceptable to have joints in ceiling panels (since they would always be reasonably easy to access down the road in case of an issue).

    Go for it.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • hot_rodhot_rod Member Posts: 14,397
    Do you have a supply and return to the location already? you mentioned not being able to get leaders back to the mech room?

    Yes you can splice the tube, use an A pex with expansion fittings to minimize pressure drop if you have a lot of splices.

    Roth panels are handy a bit of foam R value, super easy for overhead use.
    Really the R-value should be in the joist bay above the ceiling if possible. That foam layer is only R-5 per inch.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • STEVEusaPASTEVEusaPA Member Posts: 4,737
    edited September 2020
    Warmboard doesn't need the same (smaller) spacing to achieve the same output.
    I still don't understand why, after framing, you can't put up the warmboard, and run all the pex, with home runs to the basement or manifolds-in and down the walls, properly protected.
    Just like all your mechanicals, then drywall.
    The drawing you propose is too labor intensive for my liking. I also don't have a lot of faith of basically hanging the entire assembly relying on glue and drywall screws that are a lot harder to install in that set up without driving them in too far, thus reducing their holding power if they break the face of the drywall.

    As far as your lights, aren't they essentially the equivalent of old work and can be installed like old work?
  • SENWiEcoSENWiEco Member Posts: 107
    Thank @hot_rod , I have contacted Roth and asked for a sample. My concern will be how well the tubing to al sheet interface is. I have been sold on ThermoFin to this point because of this study.

    I agree with where insulation should be. I am insulating joist bays above all the panels in the basement and first floor with R14 mineral wool and the roof on the top floor has over R70 (R66 effective).

    Thanks Bob and @Alan (California Radiant) Forbes for confirming it is acceptable to have splices in this situation. That solves my problem.

    I will rough in the manifolds on each floor and leaders to each of the panel areas, then insulate, install panels per provided drawing or possibly go with premanufactured panels, then slip in tube and splice. Pressurize and then install drywall.
    Sean Wiens
  • SENWiEcoSENWiEco Member Posts: 107
    @STEVEusaPA - the issue was whether or not you can have a splice. If no splices, then it is impossible to route leaders back to manifolds once the ceilings are covered over with OSB or some form of pre-manufactured panel unless you were able to run the leader tube along the surface of the panel all the way to wherever the manifold was located. But I have areas with drop beams, led light troughs, and other obstructions, where I need the leaders to travel in the floor cavity and not along the panel surface.

    Re lights, they CAN be installed as 'old work', but this does not meet code in new construction. The driver box is supposed to be attached to structure. These are the lights The metal box is supposed to be screwed to structure. This will be impossible in my case and I need to try to get a relaxation on this requirement.
    Sean Wiens
  • ratioratio Member Posts: 2,694
    About the lights, maybe you could hang some cheap surface mount fixtures while you're waiting for the long-lead-time special order lights to come in? That way you wouldn't have to hold up your inspections…
  • SENWiEcoSENWiEco Member Posts: 107
    Thanks @ratio, I already have all 201 led lights on site. I have been thinking during the day, even IF the leads on the lights i have was long enough, you would still not want to attach the driver boxes in the assembly I will have as there would be no way to access the boxes at a later date if the fixture died. I am definitely going to need acceptance of just roughing in cable wips at this time. Project for next week :-)
    Sean Wiens
  • ratioratio Member Posts: 2,694
    Well, I don't want to be on record as recommending you tell the inspector something that is less than the truth, but sometimes you have to work around inconsiderate rules.

    It's actually a thing, to throw up a cheap place-holder while the specced fixtures come in—never had an issue getting inspections, at least around here.


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