I have a house that was built in 1956 in northern California. It has never been remodeled and has no insulation or vapor barrier in the walls. The walls get condensation on them when it is cold outside at night then warms up in the morning. Anything that is up against the walls gets wet and mildews or molds. I removed the sheet rock and found that it has tar paper in some spots and you can see chicken wire and stucco in most. How can I put a vapor barrier in at this time without having to remove stucco?
It's going to be hard to do. Since you have exposed things from the inside, the problem is that you would need some form of vapor barrier (like Tyvek)that is installed outside the wall framing. If you were to install a VB on the interior surface of the framing, all you will do is trap moisture inside the walls, causing rot. Adding strips of VB material to the back side of the stucco in-between the studs would help, but would not be a real VB as there will be too many gaps at each stud.
It could be that a solid foam fill sprayed onto the back side of the stucco would work. This is a job for a pro with the right equipment - he could also be the one to tell you if this is a good idea for a Northern California environment.
You can also try to create a vapor barrier with special interior, vapor barrier grade paints. The effectiveness of the paints is severely limited and you'd still have to caulk all the window trim, outlets and switches. If you do this you'll also want to take the 1" diameter plastic plugs out of the siding. This is where they drill those attractive holes in the outside wall to blow-in the insulation. Replace them with screened and louvered 1" diameter vent plugs. You can buy these at lumberyards. This will allow the wall cavity to dry out once the wet insulation is removed.
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