Vapor Barrier for drywall-over-plaster applications?

[joelpat]

I have an old house with no insulation, poorly (dangerious) retrofitted electrical, and a lot of cracked plaster.

Originally, I was planning to strip the walls to studs, but my schedule and budget are getting squeezed and I'm looking for ways to make the project more efficient.

I'm now thinking I should:
Leave the lath/plaster in place
Cut a 1' horizontal channel at knee height for running electrical
blow dry cellulose into the stud cavities
cover the walls in 3/8" drywall

The only problem with this plan is I now have insulation and no vapor barrier. Would it be acceptable to put the vapor barrier over the plaster and under the drywall? I seems to me this would be the same thing as vapor barrier over studs and under drywall, but I thought I would check with those who know better.

[anderson@ardex.com.tw]

Apply waterbased epoxy coating over the plaster that will provide good bonding and vapour barrier for the insulation system.

[CThomp]

Cracked plaster could possibly mean some wood damage behind the plaster.

I had lots of cracked plaster in my old house. After gutting the house off all plaster except the ceiling I discover severe rot around every window sill in the house. I had ALOT of rebuilding to do.