insulating under staple up radiant heat??

Building a house and using stable up pex in the joist spaces (actually spaces b/t web joists) under the subfloor. This is under our upper level, with conditioned space below on the mainfloor and below that with a finsihed basement. Both the main floor and basement have pex embedded in concrete.
My question is, will it be adequate to insulate b/t the joist spaces with R-11, leaving a 2-3" airspace under the tubing? Also, I bought craft faced (sp?) R-11, so do I put the paper down, toward the ceiling/conditioned space below? (I'm doing the insulation install to save $$$ rather than have the HVAC crew do it.) The finsihed floor above will be a mix of engineered wood and carpet with the special pad for radiant applications. We're using a gas high-efficiency boiler and my HVAC contractor says he will run the H20 at around 140 degrees.

Bubble wrap insulation first, shiny sid towards the floor with an air space then the r11. Or 1" styrofoam with an air gap.

insulation

The paper is a vapor barrier and has absolutely no function between floors. You could purchase plain insulation without the barrier cheaper. It just presses into postion between the joists and stays there until you install the sheetrock. That is the way an insulation company would do it.

I got the paper-backed only b/c it was on sale and with a mail in rebate ended up being $4/roll cheaper! I figured besides being cheaper, it would be a little easier to work with.

In regard to the foil bubble I've heard so many different opinions on whether it's necessary or not. It seems that most say it's not needed unless there is unconditioned space below, and that bat insulation is fine over conditioned space.

Thoughts?

foil

When the vapor barrier is needed, it goes BETWEEN the heated room and the insulation to keep moisture out of it. Otherwise the vapor will get into the insulation and freeze in the wintertime, and possibly mildew in the summer.

Try polyurea spray for insulating.It's water proof coating protects it.Many company providing polyurea spray for insulation and joints fill up.e.g ultimate linings,xtremeliners etc.

hj said:

When the vapor barrier is needed, it goes BETWEEN the heated room and the insulation to keep moisture out of it. Otherwise the vapor will get into the insulation and freeze in the wintertime, and possibly mildew in the summer.

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If the space below is semi-conditioned, like a garage, would the vapor barrier go above or below the insulation?

twilbanks said:

In regard to the foil bubble I've heard so many different opinions on whether it's necessary or not. It seems that most say it's not needed unless there is unconditioned space below, and that bat insulation is fine over conditioned space.

Thoughts?

Click to expand...

If you want to be sure the heat goes up, the double bubble will help address that ... and I would shy away from paperback insulation between heated spaces.