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radiant heat through 3.5 inches of wood floor?

simonhuynh Member Posts: 3
Hi Everyone -

I was recommended to this site by Alan Forbes, whom I believe is a regular. (hi Alan!) He suggested I pose my particular challenge to your collective knowledge and expertise.

The challenge is that I'd like to install radiant heat beneath existing flooring that is made of 2x4 douglas fir lumber planks turned on edge. The property is a unique one, and no one I've spoken to has ever heard of flooring made of that much wood. The wood looks quite nice and keeping it as is would save us the cost of more wood flooring, so I'd rather go under than over.

Alan is concerned that we won't be able to get adequate heat transfer through the 3.5 inches of wood. From what I've read elsewhere, douglas fir has an R-value of 1.2 per inch, so we're looking at an absolute thermal resistance of 4.2, maybe 4.0 after lots of sanding and then refinishing? In case it matters, the wood planks are 50 years old. On the bottom side of the house the wood planks will have seen lots of wear from weather.

So. . . can it be done?

I'm happy to attach pictures of whatever you'd like to see.

Thank you all in advance!


  • Zman
    Zman Member Posts: 7,357

    I think you can heat your house as you are describing. You will need heat transfer plates and lots of insulation under the tubing as well as at the exterior rim to make the heat go where you want it. I would expect the system to lag quite a bit as it will take time to heat up the wood.

    The real question is why?

    I have never walked on a wood floor, heated or not and noticed the temp. I don't know why, it just doesn't feel the same as heated tile or concrete floor.

    If it were me, I would install European style panel radiators. The will respond more quickly and because they will not overshoot and undershoot like a high mass floor, your system will be more comfortable and efficient.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Gordy
    Gordy Member Posts: 9,514

    With zman. Wood flooring is not a conductor as is so with tile or concrete. So the floor will feel warmer under foot because wood is an insulator/

    Radiant ceilings is another option that works well. It allows more sf of emitter, and capable of more btu output if need be.
  • bb_5
    bb_5 Member Posts: 15
    Radaint Wall

    a radiant wall may make sense as well.
This discussion has been closed.