effi wrote:

residence is slab on grade 2000 sq ft

attic has 4 inches of fiberglass insulation

no vapor barrier in attic between fiberglass and ceiling sheetrock
attached to rafters

will be adding 8" to 10" of blown in cellulose, should vapor barrier
be added between existing 4" fiberglass and drywall attached to the
rafters, before blowing the cellulose in?

or should no vapor barrier be used?



In a case like this you may be better off adding a vapor
barrier on the ceiling. Apply a paint with a low-perm
rating. Talk to any paint dealer.

A lot depends too on how cold it gets where you are.
If there hasn't been an issue with condensation, it may not
be a big factor...

Jim