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Switching one room of a hydronic radiator system to hydronic radiant heating

scottns Member Posts: 1
My house is currently heated with baseboard, hydronic heating.  We have one zone for each floor.

I am in the process of planning a renovation of the bathrooms.  Especially since the floor will be torn up, I’m thinking it would be a good time to switch the heating in just the bathrooms to hydronic underfloor heating.  (the bedrooms are wooden, not gonna be taken up)

I know that underfloor heating would ideally run on its own zone and probably at a different (lower) temperature, but routing hydronic line to the bathroom would be involved as the floor below has sealed up ceilings.  

I’m wondering if we could use the radiator loop to heat the floors?  I realize this would overheat that room.  To deal with this, could we have a bypass around the hydronic underfloor heating and valves on the bypass and underfloor heating to control relative flow thru floor?  

Has anybody seen anything like this with the two systems mixed on the same loop? Any advice or thoughts are welcome.

In case it matters at all, I’m located in upstate New York.  

Thank you


  • Jamie Hall
    Jamie Hall Member Posts: 22,162
    I won't say it's impossible. However, it would be very very difficult. The problem is the radiator loop probably runs at a much higher temperature than is safe for the floor, never mind comfortable underfoot. A mixing valve might sound attractive -- except that it needs a cooler supply, and it either needs a pump on the mixed outlet in a closed system (like your heating system) or a much lower pressure on the outlet than on either of the inlets (such as might be with a water heater mixing valve).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 20,809
    What size are the bath floors? Electric mats are an option so you can run them anytime without short cycling the boiler with tiny zones. A few hundred watts of mat will do a small bath floor
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream