Insulation question

[exeter_acres]

Hello all... Nice board M.!!
Have an older home with vermiculite (sp?) insulation in the attic, and not much at that. I want to roll out some fiberglass on top of it. (Due to potential for asbestos, I don't want to disturb the vermiculite)
My question to this knowledgeable bunch is this... What do you all recommend, plain fiberglass rolls, faced on one side with a vapor barrier rolls, or the rolls that are the nice completely wrapped in plastic sheathing for itch-free installation.

Awaiting the outpouring of knowledge! [img]/forums/images/icons/grin.gif[/img]
Thanks
Curtis

[MikePA]

Curtis,

I think you're going to want to use unfaced (no vapor barrier) insulation and roll it out perpendicular to the joists. If you use insulation with a vapor barrier, you risk having moisture laden, heated air rise up through the vermiculite, hit the vapor barrier, cool and condense in the vermiculite.

We also live in an old house and our attic had rock wool insulation poured between the joists. The rock wool had settled plus there was no vapor barrier. I could go up into the attic during the winter and see frost on the sheething. There were stains on the sheething indicating this had been going on for a while. Not good.

I could not use roll insulation because the spacing between the joists was anything but standard. So,

1. Installed eave vents (there weren't any attic vents. I also installed a termostatically controlled fan, that I could control from the attic steps, in one of the small attic windows)
2. I removed all the rock wool.
3. Rolled out a plastic vapor barrier and stapled it to the sides of the joists.
4. Cut out stiff cardboard and placed it at the end of each joist bay. The cardboard was the same height as the joists.
5. Poured in vermiculite up to the top of the joists.
6. Rolled out 6 inch insulation bats, perpendicular to the joists, across the top.
7. Used vapor barrier primer on the ceilings of all our second floor rooms.

The important task was installing the vapor barrier to keep the moisture out of the attic, where it was condensing on the clapboard sheething.

[TimSullivan]

Mike, covered it very well but I would suggest that you consider blowing in cellulose insulation. Suppliers in our area lend out a machine with the purchase of the insulation. It is a two person operation but I think it does a better job.

[jimct]

I agree - go with the second layer of plain fiberglass. Besides the moisture concerns, the vapor barrier will also make the area much more attractive to mice. They like to build nests against the vapor barrier.