Using unfaced insulation?

[MushCreek]

I'm trying to find a deal on insulation for my shop. I ran across a good deal on unfaced batts. If I use them, what should I use for a vapor barrier? Is plastic OK, or should I use something a little more breathable? What about Tyvek?

 

[Metal-Marc]

I'm trying to find a deal on insulation for my shop. I ran across a good deal on unfaced batts. If I use them, what should I use for a vapor barrier? Is plastic OK, or should I use something a little more breathable? What about Tyvek?

Plastic (6 mil) is what you want as a vapor barrier and if it's breathable, then it's not a vapor barrier.

 

[larry4406]

Plastic (6 mil) is what you want as a vapor barrier and if it's breathable, then it's not a vapor barrier.

I don't think plastic is what you want in the south.

 

[acer66]

I don't think plastic is what you want in the south.

Might be totally off but is paint not considered a vapor barrier?

 

[Metal-Marc]

I don't think plastic is what you want in the south.

Ah. Hum. Yeah. Well, it is in the North.

 

[acer66]

Ah. Hum. Yeah. Well, it is in the North.

OP’s profile says Upstate South Carolina.

 

[Metal-Marc]

OP’s profile says Upstate South Carolina.

Is he north of you?

 

[acer66]

Is he north of you?

No, I am In North Carolina.

Not sure what my location has to do with anything the OP is asking though.

 

[MushCreek]

I don't think that the kraft paper on insulation is a true barrier, ie, vapor proof. Or maybe I'm wrong; that's why I'm asking. Just like Tyvek isn't truly vapor proof; it breathes very slightly. This is in a wood barn in hot, humid South Carolina. I will run AC in the summer, and heat in the winter, but not continuously. HVAC will be a minisplit, used as needed (when I'm working out there).

 

[acer66]

This thread might help.

Vapor barrier needed? So many conflicting answers- Climate zone 7. Rockwool insulation.

I've received and also read so many conflicting answers...I'm freaking stumped. Can anyone who KNOWS what they are doing comment? I'm asking, begging, and pleading... my head cant take any more research on this and the starkly contrasting answers are driving me nuts... even from the local...

www.garagejournal.com

 

[jack stand]

Tyvek is not made or sold to be a
vapor barrier. It will shed liquid water but it's designed to transmit water vapor.
It's an air barrier.