Need a vapor barrier when drywalling?

[87GN]

I'm replacing the drywall in one of the rooms in the house. I've sealed the holes with some spray foam. After I install the insulation, do I need to put a vapor barrier on before te drywall? There wasn't any barrier when I removed the old drywall, then again, the house was built in 1959. If I need to install a vapor barrier, what thickness? Thanks.
Mark

 

[pstnbly]

Not enough information. Is there insulation and if yes what type is it?

 

[87GN]

I will be installing r15 fiberglass insulation.

 

[readhead]

Need more info. I'm not familiar with the vapor transmission in that area. Ask some reputable builders in the area about common practices in your location. Check with the building department and see if it is a requirement in your area.

 

[readhead]

What was on the wall before? Did you find any mold or damage when you opened the wall? If neither of those things you are probably good without a barrier. But I would check around anyway.

 

[Cyberbear]

Out on the left coast a vapor barrier can be optional. We used a vapor barrier over the insulation because the home was covered in aluminum siding, which can admit moisture as well as air on a windy day, evidenced by the ballooning that occurred. Once covered the walls were air tight and the floor to ceiling plastic film was working well.
For the small amount of cost, a moisture barrier may be a good idea in your application. In new construction an exterior moisture barrier is often used that serves to keep dampness away from the wall insulation.

 

[87GN]

Forgive me for not knowing the technical terms. It is going against an exterior wall. This is what I found when I took off the dry wall: r13 fiberglass insulation, approx 5 ft lengths of foam board from the top down, a foot or so of 5/8 sheet rock (looks original based off of the pictures of when the house was built in '59), and the remainder to the floor is plywood. There was no vapor barrier. There was some mold about 2 ft x 1ft at the bottom. I did find a bunch of abandoned bee honeycombs between the wall and the insulation which is why I'm going to seal whatever openings with spray foam. I'm in SE Pa.

Would pictures help? I can take some tonight and then post them.

Mark

 

[kbs2244]

The purpose of a vapor barrier in residential building is to keep the water vapor from the heated interior from entering the wall and condensing.

If you heat your house you need it.

The mold you found is what happens when you do not have it.