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tmy23

Trying to Eke out a few more degrees with Radiant

15 years ago

Greetings, Happy Holidays to all...

Did a complete gut and remodel of our kitchen this summer and installed an underfloor hydronic system. Until this week, system heated room well. Winter seemed to arrive this week and I can't get much above 65 degrees (air temperature). Manufacturers site for my flooring (wood look laminate) recommend that the "surface" that the flooring is installed on is not above 90 degrees. Temperature sensor is reading 90 degrees.

The floor construction is 3/4" red oak (original 125 year old planking), in various places building felt to level the surface, then 1/2" plywood subfloor, foam underlayment and then the laminate. The sensor is on the bottom of this cross section. It is mounted in a 4"x4" area where the metal heat transfer surface was removed, thus the sensor is mounted directly to the bottom of the red oak planking. Downward heat loss is limited by 3.5" fiberglass batts between the floor joists.

Here is my question. With a 90 degree measurement on the bottom of the red oak planking, what might the temperature of the top of the 1/2" subfloor be? Is there some heat transfer loss through this cross section, OR does the whole floor eventually reach 90 degrees. Obviously where I am heading is whether I can nudge the slab sensor limit up a bit? I don't have any way to directly measure the temperature of the subfloor without pulling up the laminate. THANKS for all help

Comments (8)

  • 15 years ago

    The answer is yes usually the temp you want it is 110, 90 is low. try not to go over 125. What product did you use? did you go with viega, wirsboro or someone else. Did you use climate panels or stapple up. if staple up do you have a barrier between floors?

  • 15 years ago

    The tubing is 1/2" Zurn. The controls, valves I believe were a pre-packaged wirsbo that the HVAC installer put in. I fabricated my own heat transfer panels with flashing that I cut to length and pressed using a form made from a 1/2" piece of PVC screwed to a plank, with a "mating" plank that had 2 pieces of 1" furing strips screwed 5/8" apart. By simply placing a piece of flashing between the positive and negative forms, and standing on the stack, I was able to press a "U" shaped channel into the flashing stock. This was then stapled up to the bottom of the oak planks enclusing the PEX in the "U". It worked well. The flashing is sized to fill the entire joist bay from joist to joist. Then as said above, I put 3.5" fiberglass right up against the metal flashing. In terms of "barrier" do you mean the foam barrier that I put down between the playwood layer and the finished laminate? I used Unison 2 in 1.

    So your saying I can raise the floor temp a bit?

    thanks

  • 15 years ago

    well when you make your own heat trasfer plate your only lookig for trouble it may not be working right ...... google radiant barrier, insulation isnt enough. but you should be able to go to 120 no propblem check with the manufactors specs.

  • 15 years ago

    One thing you might want to rule out is having air bubbles stuck in one point of the tubbing. If it used to work well them it became less effective, it could be because air bubbles formed. They weren't there when the system was first installed. They form latter. water breaks down into the two gases that they are made of. I think that's how it works, but I'm not sure about that part. I am sure that I had areas of my system that stopped working. I raised the temperature a lot. It didn't work any better. I bled that run of tubbing and it worked better.

  • 15 years ago

    I see a bunch of issues (no experience with radiant myself).

    Seems like the foam is adding a layer of insulation so the temp reading for you sensor is probably higher that the laminate temp. Based on that I think it would be safe to raise it a bit.

    I also wonder about the ability of radiant to work in such a non conductive medium (wood/foam). I know it can be made to.

    Are the loops laid out/spaced correctly, who engineered (or lack thereof) the system, is there enough capacity/zones

  • 15 years ago

    The HVAC installer who did the piping to the radiant panel, and installed the sensors and programmed the system told me what size tubing to use, how to run, etc. etc. As I was saying up earler in this post, it seems the 1 1/4" wood and then foam underlayment, would prevent 100% heat transfer, so the top of my floor might be cooler. I wish I had thought of drilling out a little hole in the floor to put the sensor right up against the laminate. I raised the floor temperature max from 90 to 95 degrees and the room air temp is now up to 67 with an outside temp of 36 degrees. I am tempted to take it up another 5 degrees to 100 which should get me close to 69-70 with an outside temperature of 30. Again, I just didn't want to screw up the flooring, but I don't think the floor is getting up to 100 on the top side?

  • 15 years ago

    If you could run some tubes up a wall in that room, that could help. Also, did you insulate the part of the tubes that are not under the floor? If not, it sounds like the water could be losing all it's heat (radiating) in areas other than that room. When it gets to that room, it is insulated by the foam in the floor and not losing or radiating heat.

  • 15 years ago

    On average insulated homes with kitchen cabinets and appliances consuming a % of the floor available in kitchens for radiant it is not uncommon for the need of supplemental heat or a connecting room beefed up to cover the difference.

    The design/heat loss calcs would have disclosed that.