wrote in message
oups.com...
I have put in new insulation, but have a question about vapor barriers
and some additional foam insulation. Here's my "recipe" that I'd like
some feedback on. Starting from the interior out, the following
materials will be used on all exterior walls AND ceiling:

Tongue & groove knotty pine 3/4" Foamular insulating foamboard 6
mil plastic R-19 kraft-faced insulation Durovent (to provide
airflow from soffit to peak).

1" FOAMULAR® is only R-5. That plus the R-19 (you should use unfaced) is
only R-24. I thought you need to be R-30 nowadays.

My questions a

1) If I put the plastic over the kraft-faced insulation, am I creating
a vapor "trap"?

Yes.

2) If the above answer is "Yes", will the foam board result in the same
vapor lock situation?

Yes.

My purpose for wanting to use the plastic is to better seal the walls
from drafts, especially since I'll be using t&g wood for the interior.
The foam board is just to add a little more seal and more insulation.
My concern is that I could create a situation where I'm trapping
moisture and thus encouraging mold growth and decay.

Can anyone with experience/knowledge about the subject provide some
feedback?

FOAMULAR® is already is a vapor barrier. You can simply seal the seams with
a non-permeable tape.

I have a Cape Cod style home located in Michigan. I gutted one of the
upstairs bedrooms, removed the collar ties and reinforced the rafters
to allow for a cathedral ceiling.

This sounds a bit odd. Reinforcing the rafters doesn't seem to be a
substitute for collar ties. What did you do here?

-al sung
Rapid Realm Technology, Inc.
Hopkinton, MA