Radiant floor in joists

DaveGateway

graphs

rb,
Thanks for the graphs!
What I see is about a 65:35 ratio between radiation:convection at the following temps.
Heated floor at 80*, air & unheated walls at 68*
(radiation 11btuh/ft2 : convection 7btuh/ft2)
11 + 7 = 18? I thought it would be around 24btuh/ft2?
Maby my unheated walls are too warm?
Thanks BP

hr

How would

get out of the slot, with the tube, to cross over to the next slot? Can tou still get under this floor? If so transfer plates from below may be the best approch.

I'd also worry about hitting nails with the router. sometimes they are close to the edge of that diagonal planking. I think the nailed down hardwood would more than make up for the diagonal strength that might be lost by routering the space

hot rod

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hr

How would

get out of the slot, with the tube, to cross over to the next slot? Can tou still get under this floor? If so transfer plates from below may be the best approch.

I'd also worry about hitting nails with the router. sometimes they are close to the edge of that diagonal planking. I think the nailed down hardwood would more than make up for the diagonal strength that might be lost by routering the space

hot rod

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enough to be dangerous

ends

yes, crossing at the ends is a tricky problem.

The reason I want to avoid placing under the floor boards it to avoid their R value and thus lower the water temp needed.
It seems to me that if you place an insulating object on the heated floor then the surface temp of the floor will approach the temperature of the water in the pipes. If the water temp is 120F then the surface of the HW floor could be near 120F if you happen to toss a pillow on the floor or if you happen to lie on the floor. The lower the water temp needs to be then the less important this effect will be.
If you avoid the subfloor R value then the total Rvalue of the floor will go down by at least 1/2. If the under subfloor piping requires 120F then the over subfloor piping would require 95F for the same heat output. I think I'm right, am I? Everyone seems to assume that the floor temp will be its free air value. No one talks about what happens when its temporarily insulated.

pasquale

hr

ends and up R value

you are correct 3/4" of subfloor would cost you R-0.8. It does buy you a better heat spread, less striping) than installing finished floor directly on the tube.

Generally the floor SURFACE temperature should be 83° or below. With transfer plates under the subfloor and 3/4" of hardwood, 120° supply should still get you 20 btu/ sq. ft or more. What is the heat load of the room you are considering. This would be the first, and most important step. Define the load then it will help you decide if the on top, or under subfloor would be sufficient.

What will your heat source be? Generally boilers or DHW's need to run above 120 to prevent condensation. Lowering the supply to 95° would require a mixing valve, or mixing system.

hot rod

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