Quote:
Originally Posted by Vlad
I just want to remind where all discussion is coming from. Radiant hydroponic heating system is low or even very low temperature heating system. This makes possible using heat pump for heating water. Performance and COP of heat pump depends on temperature difference (outside/inside). The main goal to make water temperature as low as possible. This is why adding R value to your floor covering will lead to water temperature increase. My installation is hybrid above floor but I have extra layer of plywood above pex. In my installation I have 5/8 plywood and hardwood or tiles (about 20%) my water temperature was max @ 95 F.
I don't think it is a great idea to put tiles or carpet or any other flooring right on top of pex.
I am absolutely happy about performance of my heating floor system.
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I agree with everything you said. The only place I differ is regarding my particular house and a lot of houses similar to mine, one's with an existing diagonal planking subfloor. The only other choice for me is pex on top of underlayment, which I agree isn't too good.
But it really would not make it difficult to have low water temperatures in my system. Just as Mr. Bean says, run pex closer together. You get more heat with the same temperature. Plus if one is really anal about it, on my system with with two wood layers before floor covering you just might be able engineer one system that accepts the two insulation values of say R=2.7 (3*0.9 wood floor layers) and R=4.3 ((2*0.9) + 2.5 a single carpet layer with 2 wood layers.) That is a difference ratio of insulation values of about 1.6. That should easily be doable in one carefully engineered system for a floor covering change by a future owner. If one originally installs 3/4 hardwood floor covering then engineer the system so it has the reserve to heat 1.6 times the current total insulation value if carpet is installed later. Options are always good.