Just for clarification, I stapled the barrier to the underside of the attic/roof joists – works great for the warm weather and still waiting to see what will be yielded for the winter. Since I had a lot of barrier material left over, I thought this might be a good way to amplify the R value of the existing fiberglas insulation.

Thanks again!

Thanks for the comment. I’m a little unclear. You mentioned “under side of my attic rafters” – did you staple it up or lay it out over the insulation? As for putting foil below the insulation, it will work. By using a solid product (non-perforated) you would have both a vapor barrier (stop moisture and air) AND a radiant barrier as long as you can get an air space on one side of the foil. Typically this is done by running radiant barrier across the studs (walls) or bottom of joists (ceilings), THEN running furring strips (usually 1″x2″s) perpendicular to the studs or joists. Then, you would attach sheetrock to the furring strips.

The end result coming from the inside out would be: Sheetrock => Air Space due to furring strips => Radiant Barrier Foil => Insulation

Does this help?

Ed

My question is, would I also benefit from installing a non-perforated barrier BELOW my attic floor insulation, to deflect radiant heat back towards the living space (if the barrier isn’t coming in direct contact with cold air, would moisture ever develop?)? I believe the top layer has already reduced the cold air looping effect you describe so well, so this seemed a reasonable approach to me.

Thank you!