Finishing a vaulted ceiling, double vapor barrier?
Our house is built with clearspan metal trusses with purlins fastened on top of the trusses. When it was built, a layer of some of that reflective foam insulation was put over the purlins and then the metal roof went on top of that.
Now we are wanting to finish the inside, and I am wondering how it should be insulated. We were thinking of filling the stud cavities with fiberglass insulation and then putting more of the foam insulation (its about 1/4" thick) underneath that. We would then put sheet rock under the foam insulation. So it would be the sheet rock, a layer of the foam insulation, fiberglass in between the purlins, another layer of foam insulation on the purlins and then the metal.
My question is, would that be bad to have two vapor barriers?