I am looking to retrofit a hydronic radiant heating system to the first (ground floor and basement of my house. For the first floor the plan is to install the system under the subfloor by snaking the tubing between the joists. The basement floor is slab concrete without any insulation below the slab. I don't have any ceiling height to lose so adding insulation does not seem like a good idea. Further, there is a mild moisture issue with the floor so this just seems like a bad idea.

I was thinking of running additional tubing in the ceiling. I am completely unfamiliar with the concept of radiant ceiling heating and not sure if it can be combined with radiant floor heating. Can I essentially run one set of hydronic radiant heat tubing to heat the ceiling of one room and the floor of the room above it.

  • @isherwood I tried to clarify my question. Basically, I want to know if I run one set of hydronic radiant heat tubing to heat the ceiling of one room and the floor of the room above it. – StrongBad Apr 13 '17 at 20:03
  • I would think if you are using radiant floor heat you would have some ceiling heat already. Cable heating was big here in the Pacific northwest when power was cheep. It will work to add ceiling heat but remember heat rises so your upstairs floor heat may need to be turned down. – Ed Beal Apr 13 '17 at 22:03
  • @EdBeal Heat does not rise. Heat moves from high temperatures to cold temperatures. Hot air rises. In a subfloor/ceiling cavity, there's little room for convection, so not likely a problem there. You also don't rely on convection for a radiant ceiling, which is why they are much hotter than radiant floors. – Hari Ganti Apr 14 '17 at 21:58
  • Ok try and not insulating above a cable or radient heat system in the ceiling and see how much is in the room below. – Ed Beal Apr 16 '17 at 22:48

You'd need custom heat spreaders, and it still won't work well

The heat spreaders used for hydronic systems only spread the heat along one face (so either a subfloor or the ceiling drywall). You would need to get a custom heat spreader for a single tube to do both.

A hydronic radiant ceiling also requires much higher temperatures than a floor does, so you'd have an uncomfortably hot floor or a rather ineffectively tepid ceiling. Neither is ideal.

You could run parallel systems between ceiling/floor joists

Two systems, with different temperatures, could be placed in parallel in the same space between joists. I can only speculate that it could work, but I've never heard of this before, so you might be venturing out a bit here.

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