On Sat, Dec 10, 2011 at 8:45 PM, <shop-talk2 at mcfetridge.org> wrote:
> You could use a water vapor permeable plastic membrane (Tyvek and cheaper
> equivalents) that would still let the walls breath, but keep the flow of air
> to a minimum -- basically what it does as a house wrap.
I had something similar in mind for my attic. I currently have a layer
of blown insulation (from 1976), and then a second layer of R38 batts
(2' X 4' each) running opposite the joists. I'm thinking of running
lengths of Tyvek sheeting across the joists from gable to gable (under
the newer layer of batts) to reduce upward drafts.Of course, the
existing batts don't provide much of a vapor barrier, but I am more
concerned about air infiltration.