Special Insulation for radiant floor heating?


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Old 11-30-09, 06:42 PM
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Special Insulation for radiant floor heating?

Just finished installing radiant floor heating under my living room, kitchen and dining room. I must say I love it but right now while the 1st floor is 65degrees the basement is 75+.

I have 1/2" pex tubing back and forth between my joists then snapped into a aluminum strip which spreads the heat. I need to insulate the joists to keep the heat from coming down into the basement and making more of it go up through the floor.

I have heard 2 things. Use regular R13 insulation kraft face. About $9 a roll.
and
Use R11 insulation with a foil face, about double the cost.

Is the foilf face needed? Even if I have those plates to spread the heat?
Would the regular R13 be ok? or no?

Thanks
 
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Old 11-30-09, 10:35 PM
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The amount of insulation will somewhat depend upon the use of that basement space. If it is not used and therefore doesn't need to have any extra heat, then much more insulation than either suggestion would be recommended.

If you want some heat to spill over from above, then less would be acceptable.

Now, if you are going to sheetrock the ceiling below, then foil faced rigid insulation is an option. No sheetrock, no rigid, fire codes.

So, your question. Either r-13 or r-11 are much too thin, too much heat will go to the basement. By the time you consider the effect of the joists on the total insulation, you would have less than r-10 total. The foil serves as a radiant barrier, so I would go with r-19, foil faced as a minimum, with the foil facing stapled over the edges of the joists as neatly as possible.

Adjust as needed to balance where you want the heat to go.

Bud
 
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Old 12-01-09, 06:39 AM
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id rather have all the heat go up thourgh the floor. a chilly basement is ok right?

R19 foil face is .55/sqft and would cost about $550 to insulate the 1st floor

i have also seen Aluminum Foil Reflective Barrier here Our Large Selection Of Radiant Heating Materials Can Benefit Your Project about 2/3 of the way down the page. Could i put that up then R13 rolls on insulation? Total cost would be around $450

is one better then the other?

I would still like to maintain some joists space incase i need to run wires in the future.

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.
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what would happen if i used just R13. the basement would still get warm and id lose heat from going upstairs?
 
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Old 12-01-09, 08:02 AM
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If your basement is well air sealed and insulated around the rim joist and exposed foundation, then any lost heat is really not totally lost. But, if your foundation walls are not insulated, you need to keep that heat upstairs. If you are not installing drywall, then plan it so more can be added later. Radiant barriers work it both direction and only one is needed. They will either reflect heat back to where it came from, or not transmit heat to the areas below when used below the insulation. Again, one can be added later. So, if budgets are tight, been there, then tuck some r-13 kraft up into the cavity and staple it to the sides of the rafters. That's a bare minimum, but you will be able to judge your energy use and basement temperature over the winter. Your joists are probably 2x10 so you have plenty of space to play with. Bud
 
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Old 12-02-09, 09:35 PM
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here are 2 pictures of what i have.
in one spot i put some left of R19 i had and in another I put R30. I was thinking maybe i could tell a difference in heat through the floor to the tile but after it was up I realized its probably not enough there to see a difference.

So what i would do is get R19 foil back and put that in there. Now the foil would touch the pex tubing and the insulation would be facing down right?

Thanks again

 
 

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