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Radiant Wall - Ceiling -Floor Assistance

NYplumber Member Posts: 503
Good afternoon wallies,

Doing some design work for a house we are working on next week.

House will have cast iron radiators oversized for lower water temps. Three rooms require radiant to work with decor and lack of wall space.

Front walk in, kids bathroom, & kitchen.

Front walk in is 20 sq ft with a load of roughly 900btu. For this we are contemplating ceiling radiant with possibly adding floor radiant too.

Main kids bathroom 40 sq ft, 1100btu.

Kitchen, still awaiting counter and cabinet layout.

Questions: ADS software wont work on my computer so limited to mathematics.

I think the front entrance can be heated radiantly.

For the bathroom we would like to do wall radiant (maybe floor too in the mud) with plates like the attached photo. Cant use Roth panel as the one inch loss in wall thickness will place the tub drain over a 2x12 beam. Wall will be spray foamed so carving out a small channel for the plates would work well.

Input would be helpful as I already spent much time searching and finding factors of .7-.8 btu per sq ft for tw-tr from the idronics6.

Lastly, which plates are of heavy gauge for the wall? The only plates I have used were Uponur extruded.

<img src="http://www.greenpowersystems.org/wp-content/uploads/2013/02/radiant_heat_11480.jpg" alt="" />

Thanks in advance.


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Hey, I recognize that job...

    Moe, I suspect you "borrowed" that picture from the DOE web site. That is one of the first radiant wall jobs that Advanced Hydronics (my former employer) installed. It was done for Habitat for Humanity on a project that was underwritten by the National Renewable Energy Laboratories (NREL). We developed a "template" and used a 3/4 H.P. router with a 7/8" bull nose bit to plow the grooves into the face of the studs so that the light aluminum plates sat perfectly flush to the face of the stud, then packed high density fiber glass insulation between the studs to keep the plate in firm contact with the drywall. If you look through the studs, you can see another radiant wall in the background. It is identical to the one in the foreground, except that it is on both sides of the wall. You can see the leads going to the Oventrop wall box mounted TRV's. This building achieved the highest HERS rating for the State of Colorado when it was completed. I am sure it has been overshadowed now (some 15 years later…) but I am also certain that it is one of the most comfortable houses HfH has ever built. Jim Lovell, former astronaut, was the then director of HfH, and I got to meet him. Fun project all around.

    Shortly after those pictures were taken, we yanked the nail guards off. We used "Story Poles" to show the volunteer drywall installers where is was safe to place fasteners, and we had NO tube hits. Had we left the nail guards on, it would have negatively affected the output of the panels.

    Anyway, what is it that you are looking for her? About the only information I have seen is some stuff that Siggy did on the output of these panels based on delta T between wall surface and room temperature. He also has them out there for floors and ceilings. Is that what you are looking for?

    Thanks for thinking outside of the floor box, and I think you and your customer will be impressed with the end result.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • SWEI
    SWEI Member Posts: 7,356
    Nail plates and wall heat

    We had a bit of a tussle a couple years back with an inspector over those.   Finally got a letter out of Watts Radiant stating that the transfer plates had to be in contact with the sheet goods in order for the system to work properly and he relented.

    Eight foot plates are less work than four footers for horizontal tubing runs.  Radiant Engineering up in Bozeman sells them in both light and heavy gauge and can help with the math as well.  Give them a ring.
  • NYplumber
    NYplumber Member Posts: 503

    Barrowed from GreenPowerSystems.org. Where they barrowed it is beyond me.

    Mark, so I guess I have all the math I need as far as how many sq ft of wall space. How about calculating the driving temp of the water behind sheetrock? Chances are we will have way more wall coverage then needed, and boom we are in to efficiency land for the boiler.

    I tried to get him to do radiant ceilings on the first floor but he got cold feet (pun intended) when he heard the cost of warmboard.
  • NYplumber
    NYplumber Member Posts: 503

    Thanks for the lead.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    edited March 2014
    Suggest you contact...

    The tubing manufacturer of your choice. I'd call Uponor in my case, and have them tell me required temperatures and flow rates to achieve your goal.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Zman
    Zman Member Posts: 7,569

    Go to this link and download CDAM.

    A great source.


    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein