Lack of attic vapor barrier with cellulose insul

[Jerry Simon]

Your thoughts on such?

[David Meiland]

What would you normally expect as the vapor barrier--poly on the framing, kraft on fiberglass batts, VB primer on the ceiling?

[Jerry Simon]

What would you normally expect as the vapor barrier--poly on the framing, kraft on fiberglass batts, VB primer on the ceiling?

Yes

[Tom Raymond]

How deep was the cells? Once you get to R-45 or so (15" applied, 13.3" settled) it pretty much is an air barrier.

[Jerry Simon]

Once you get to R-45 or so (15" applied, 13.3" settled) it pretty much is an air barrier.

That's what I've been told. Can't recall ever seeing such, though (no vapor barrier). Usually see fiberglass batts w/VB covered with a layer of cellulose.

[kurt]

I think it's better without if its deep.

[John Dirks Jr]

I never see VB if its loose fill only.

[hausdok]

Hi,

Cells is a very good vapor barrier in and of itself. It allows water vapor to diffuse slowly through it and evaporate on the cold side of the insulation, without allowing a lot of heat bypass leakage, and while doing a good job preventing wind infiltration. As long as you've got good attic ventilation on the cold side of the batting you'll be good.

Using a vapor barrier on the ceiling plane would work but if it were on top of the insulation - say in a layer of kraft-paper-faced fiberglass batting - it might cause moisture issues within the insulation if the vapor trying to pass through that batting is being cooled to dewpoint.

ONE TEAM - ONE FIGHT!!!

Mike