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is there a limit on how thin thermal mass can be - above floor panels

WillC
WillC Member Posts: 23
edited December 2020 in Radiant Heating
Hi,

I am reading the excellent Modern Hydronic Heating book and I have some questions.
When comparing a product like Warmboard, the aluminium is .025" thick, another product like Ecowarm is only .01" thick. That is a 85% difference of thickness. Is Warmboard 85% more effective?

if I understand right, the thinner the thermal mass is, the more reactive to inputs the floor is, the thicker the thermal mass is, the better it is at dampening the variation of temperatures of the room.

I have seen products with very little thickness of aluminum, so thin I would be worried to scratch it during the construction.

I dont want to do that but If I was very careful, could I install a layer of aluminium from the roll I have in my kitchen, on top of some 3/4 plywood, run my PEX in a channel and get almost the same heat transfer as a Warmboard product but with just less temperature dampening?

Is there a limit on how thin we can go?
Is there a thickness of aluminium that is agreed to be ideal for above floor panels?

Thanks

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,168
    The aluminium panel isn't there for thermal mass. It has almost none, in any thickness. It's there to ensure the heat is distributed more evenly into the floor structure.

    If you were very careful, used heavy gauge aluminium foil, and made sure it was in tight contact with the pipes, I expect it might work almost as well as Warmboard. The real trick is the "tight contact with the pipes". If it's not in good contact, it might as well not be there at all.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    edited December 2020
    I think either @hot_rod or @Ironman once posted something showing the various radiant buildups shot with a FLIR showing how well they transfer heat.
    It might have been a study done by someone in VA which made me think it might have been @Ironman.
    steve
  • hot_rod
    hot_rod Member Posts: 22,022
    From the testing I have seen, the thicker gauge seems to conduct the temperatures our to the edges best.
    But the bigger transfer happens where the tube and plate come in contact
    . Or not🤭 That is where the ThermoFin product excels, the tight tube contact. I’m not sure the foil would be worth the effort?

    Here is one study, I have some FEA of the plates somewhere also.

    This IR is ThermoFin compared to rubber tube staple up.

    https://radiantdesignandsupply.com/theheatexchanger/2013/3/4/comparative-infra-red-study-of-heat-transfer-plates
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • WillC
    WillC Member Posts: 23
    Thanks for the answers guys.
  • woobagooba
    woobagooba Member Posts: 186
    Bump for WillC. I'm in the middle of a decision re: Ecowarm versus Warmboard R (we are going over the sub-floor and want the aluminum on top). Which did you end up choosing and why? Cheers
  • hot_rod
    hot_rod Member Posts: 22,022
    Depending on your floor coverings the Roth panel is a nice system. The 3/8 tube version is only 1/2" thickness.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • TAG
    TAG Member Posts: 755
    The Roth panel looks very interesting ..... I have only used the Warmboard S. I have used in many projects and it works very well.

    Most important: What BTU do you need ? Look at the product to assure the product will deliver at the water temp you need. Example: I went with the thicker ThermoFin not because the thiner would not work ... the thicker would work at the lower temps of the Warmboard in the rest of the house.
  • woobagooba
    woobagooba Member Posts: 186
    hot_rod said:

    Depending on your floor coverings the Roth panel is a nice system. The 3/8 tube version is only 1/2" thickness.

    Hey Hot Rod. What type of finished flooring were you putting over your Roth installs?
  • hot_rod
    hot_rod Member Posts: 22,022

    hot_rod said:

    Depending on your floor coverings the Roth panel is a nice system. The 3/8 tube version is only 1/2" thickness.

    Hey Hot Rod. What type of finished flooring were you putting over your Roth installs?
    The homes that I used the Roth on had 3/4 T&G flooring nailed down. The bathrooms has cement board screwed over the panel, then tile thinset down.

    One mistake on the hardwood was the floor installer insisted on putting down a red rosin paper over the Roth. I traced all the tubing with a magic marker but they still hit a couple. I had 100 psi air on it so we found them right away. Blamed it on that strong Show Me weed :)

    On the tiny home I first put 1/5" underlay then glued down 12" cork tiles.
    Not happy with the cork staying flat, I removed them and floated a thin bamboo engineered flooring over the underlay.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • TAG
    TAG Member Posts: 755
    Hot rod .... what did the floor guy think the paper was doing ?

    Being an old house guy I have works on many old houses where the flooring is direct to the subfloor ... never understood the Rosin paper. The floor guys say it cuts down on noise ? Maybe it does with plywood ... but we have ripped up a few of those as well.

    Warmboard makes a point of saying .. No paper.
  • hot_rod
    hot_rod Member Posts: 22,022
    edited February 2021
    TAG said:

    Hot rod .... what did the floor guy think the paper was doing ?

    Being an old house guy I have works on many old houses where the flooring is direct to the subfloor ... never understood the Rosin paper. The floor guys say it cuts down on noise ? Maybe it does with plywood ... but we have ripped up a few of those as well.

    Warmboard makes a point of saying .. No paper.

    Plenty of those old hardwood system I have worked on had asphalt impregenated felt paper under them also. The reasoning I heard was a moisture barrier to prevent moisture from coming up from below. Also a slip sheet for movement noise.
    I have not looked at the hardwood flooring association websites lately, the used to require that paper under solid hardwood, maybe it has been revised?
    I would guess the solid aluminum layer on WB would serve the same purpose.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • TAG
    TAG Member Posts: 755
    Lots of felt ..... that I could see years ago with random board subfloors and dirt floor basements. Interesting fact --- there is only a couple of companies that still make the true 30lb felt. It was at one time very common and made a great VB ... it still allows some moisture to pass. I had to use it a couple years back when I replaced a slate roof .... comes from Canada