kraft-faced insulation over blown-in cellulose

[fixerupperinmaine]

I am laying R-38 insulation batts over existing blown-in cellulose (enough blown-in that the floor joists of the attic cannot be seen). These batts are kraft-faced because I could not get the unfaced.

Everything I read says to place unfaced over existing.

A few sites suggest that if faced, one should take the kraft paper off, or slash it and lay the kraft paper side down.

One site says that if no vapor barrier is present next to the ceiling (which is my case - some places I can see right through to the great Maine outdoors...), one may be added beneath the second layer of insulation as long as the insulation on top has at least twice the R-value of that below.

A friend (a builder) says that he's more concerned about heat loss from the cold attic and that I should keep the kraft paper facing up so that there is no heat loss. He says that the kraft paper breathes, unlike a real vapor barrier.

Then again... the sites I've read say that kraft paper acts as a vapor barrier.

A few sites mention that there should be no kraft paper facing up because of fire-safety concern.

I'm leaning toward taking the kraft paper off, but my friend's concern seems valid... then again there's the fire safety concern...

arrrrgggh! Help!

confused in Maine...

[HayZee518]

Cellulose insulation is treated with a fire retardant which will slow down burning - but it won't eliminate fire. Fiberglass batts kraft faced or not kraft faced will melt then burn! If your attic electrical is solid then why worry about fire? Sure fire is on everybody's mind as what not to have but unless you have reason to be concerned - i.e. a fireplace, a chimney fire, etc don't worry about it!

[fixerupperinmaine]

Thanks for the reply. There is a chimney through the attic. I just had some IC rated halo lights put in, so I guess this means that the electric is solid up there, though I don't know what's been done before I moved into this house...

But what about the whole vapor barrier concern? By keeping the kraft paper on, am I, in effect, preventing any moisture from evaporating?

[HayZee518]

let it breathe! there's moving air in the attic

[fixerupperinmaine]

Thanks again for your message.

So (sorry if I'm dense), are you saying "let it breathe" ie... the batts should be unfaced?

[HayZee518]

actually yes - if you have gable vents to let out the hot air there is moving air up there.

[Drywall DIY Guy]

Take the paper off

Yes, as mentioned, let it breath. Otherwise, moisture can build up since the vapor from your living space will condense when it hits cold temps. Then the moisture dampens the insulation, causing it to perform poorer and possibly leading to mold. Damp insulation has less tiny air pockets, and air pockets make a nice insulator in themselves. So take the paper off. A moisture barrier should only be placed right next to the heated surface - this stops moisture from getting into your insulation.

[fixerupperinmaine]

Thank you both for your help. I feel so much better. (And yes, I do have gable vents.)

At some point soon, I'll post another question about basement crawl space, vapor barrier, and insulation but I'll finish this project first!