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Hybrid Radiant-Forced Air System

JulieFig Member Posts: 2
I am building a 2-story, 2400 sq ft and wish to use radiant heating for comfort, but the bids seem insanely expensive.  Is it reasonable to combine hydronic floor heat on the bottom (where we spend most of our time) with forced-air on the top?  I suspect we may not need to heat the second story much in our mild SF bay area climate, but can the ducting be part of the ventilation system that we'd need to have anyway?  I guess this is really two questions..   


  • Hybrid System

    You won't need ducting for ventilation on the radiant system; it's just not necessary.

    Yes, you can have radiant downstairs and forced air upstairs.  If you have a downstairs slab, most of the cost can be be for the upstairs radiant because it's more costly to install in a raised floor vs. a concrete slab.

    I'm in Berkeley and even though we have a mild, Mediterranean climate, the moisture in the air makes it feel colder than it is. 
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • JulieFig
    JulieFig Member Posts: 2
    2-Story Hybrid

    We have a crawl space under the ground floor, and had bid a low-mass system using PEX, grooved wood, and aluminum, but if we do radiant on the first floor only, mas use gypcrete instead.  In either case, we would install ducting for an ERV and fresh air.  The forced air upstairs would be to avoid having the weight of a hydronic system on the second story.  Like I said, I suspect we won't have to actually run it much, as every 2-story house i go into seems to be hot upstairs, cold downstairs.  Of course these all had forced-air throughout.

    Do you have any direct experience with a hybrid system in our area?
  • zacmobile
    zacmobile Member Posts: 211

    Have you thought about panel radiators for the second floor? They give off a wonderful radiant heat and they could be sized to run at or close to the water temperature required for the lower floors so piping would be simplified.
  • Floor Treatments

    "PEX, grooved wood and aluminum" is a system usually used for remodeling in an existing structure...........and it's labor intensive and expensive.  Gypcrete is an excellent way to embed tubing and provides good soundproofing, but it's expensive as well and often requires re-engineering the floor for the added weight.

    Warmboard is a product that is perfect for new construction.  It comes in 4' x 8' sheets and acts as the subfloor for your house and also as a substrate for radiant tubing.


    You can send Warmboard your plans and they will engineer and detail the system for you.  We've done quite a few Warmboard jobs, most recently a small house in Berkeley earlier this year.  The owner had her carpenter install the Warmboard and she laid down the tubing herself. 

    To answer your question, yes, I've done a few hybrid (radiant/forced air) systems.  They work well and reduce the final cost of the heating system.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
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